drm/i915: Replace the pinned context address with its unique ID

[deliverable/linux.git] / drivers / gpu / drm / i915 / intel_lrc.c

/*
 * Copyright © 2014 Intel Corporation
 *
 * Permission is hereby granted, free of charge, to any person obtaining a
 * copy of this software and associated documentation files (the "Software"),
 * to deal in the Software without restriction, including without limitation
 * the rights to use, copy, modify, merge, publish, distribute, sublicense,
 * and/or sell copies of the Software, and to permit persons to whom the
 * Software is furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice (including the next
 * paragraph) shall be included in all copies or substantial portions of the
 * Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
 * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
 * IN THE SOFTWARE.
 *
 * Authors:
 *    Ben Widawsky <ben@bwidawsk.net>
 *    Michel Thierry <michel.thierry@intel.com>
 *    Thomas Daniel <thomas.daniel@intel.com>
 *    Oscar Mateo <oscar.mateo@intel.com>
 *
 */

/**
 * DOC: Logical Rings, Logical Ring Contexts and Execlists
 *
 * Motivation:
 * GEN8 brings an expansion of the HW contexts: "Logical Ring Contexts".
 * These expanded contexts enable a number of new abilities, especially
 * "Execlists" (also implemented in this file).
 *
 * One of the main differences with the legacy HW contexts is that logical
 * ring contexts incorporate many more things to the context's state, like
 * PDPs or ringbuffer control registers:
 *
 * The reason why PDPs are included in the context is straightforward: as
 * PPGTTs (per-process GTTs) are actually per-context, having the PDPs
 * contained there mean you don't need to do a ppgtt->switch_mm yourself,
 * instead, the GPU will do it for you on the context switch.
 *
 * But, what about the ringbuffer control registers (head, tail, etc..)?
 * shouldn't we just need a set of those per engine command streamer? This is
 * where the name "Logical Rings" starts to make sense: by virtualizing the
 * rings, the engine cs shifts to a new "ring buffer" with every context
 * switch. When you want to submit a workload to the GPU you: A) choose your
 * context, B) find its appropriate virtualized ring, C) write commands to it
 * and then, finally, D) tell the GPU to switch to that context.
 *
 * Instead of the legacy MI_SET_CONTEXT, the way you tell the GPU to switch
 * to a contexts is via a context execution list, ergo "Execlists".
 *
 * LRC implementation:
 * Regarding the creation of contexts, we have:
 *
 * - One global default context.
 * - One local default context for each opened fd.
 * - One local extra context for each context create ioctl call.
 *
 * Now that ringbuffers belong per-context (and not per-engine, like before)
 * and that contexts are uniquely tied to a given engine (and not reusable,
 * like before) we need:
 *
 * - One ringbuffer per-engine inside each context.
 * - One backing object per-engine inside each context.
 *
 * The global default context starts its life with these new objects fully
 * allocated and populated. The local default context for each opened fd is
 * more complex, because we don't know at creation time which engine is going
 * to use them. To handle this, we have implemented a deferred creation of LR
 * contexts:
 *
 * The local context starts its life as a hollow or blank holder, that only
 * gets populated for a given engine once we receive an execbuffer. If later
 * on we receive another execbuffer ioctl for the same context but a different
 * engine, we allocate/populate a new ringbuffer and context backing object and
 * so on.
 *
 * Finally, regarding local contexts created using the ioctl call: as they are
 * only allowed with the render ring, we can allocate & populate them right
 * away (no need to defer anything, at least for now).
 *
 * Execlists implementation:
 * Execlists are the new method by which, on gen8+ hardware, workloads are
 * submitted for execution (as opposed to the legacy, ringbuffer-based, method).
 * This method works as follows:
 *
 * When a request is committed, its commands (the BB start and any leading or
 * trailing commands, like the seqno breadcrumbs) are placed in the ringbuffer
 * for the appropriate context. The tail pointer in the hardware context is not
 * updated at this time, but instead, kept by the driver in the ringbuffer
 * structure. A structure representing this request is added to a request queue
 * for the appropriate engine: this structure contains a copy of the context's
 * tail after the request was written to the ring buffer and a pointer to the
 * context itself.
 *
 * If the engine's request queue was empty before the request was added, the
 * queue is processed immediately. Otherwise the queue will be processed during
 * a context switch interrupt. In any case, elements on the queue will get sent
 * (in pairs) to the GPU's ExecLists Submit Port (ELSP, for short) with a
 * globally unique 20-bits submission ID.
 *
 * When execution of a request completes, the GPU updates the context status
 * buffer with a context complete event and generates a context switch interrupt.
 * During the interrupt handling, the driver examines the events in the buffer:
 * for each context complete event, if the announced ID matches that on the head
 * of the request queue, then that request is retired and removed from the queue.
 *
 * After processing, if any requests were retired and the queue is not empty
 * then a new execution list can be submitted. The two requests at the front of
 * the queue are next to be submitted but since a context may not occur twice in
 * an execution list, if subsequent requests have the same ID as the first then
 * the two requests must be combined. This is done simply by discarding requests
 * at the head of the queue until either only one requests is left (in which case
 * we use a NULL second context) or the first two requests have unique IDs.
 *
 * By always executing the first two requests in the queue the driver ensures
 * that the GPU is kept as busy as possible. In the case where a single context
 * completes but a second context is still executing, the request for this second
 * context will be at the head of the queue when we remove the first one. This
 * request will then be resubmitted along with a new request for a different context,
 * which will cause the hardware to continue executing the second request and queue
 * the new request (the GPU detects the condition of a context getting preempted
 * with the same context and optimizes the context switch flow by not doing
 * preemption, but just sampling the new tail pointer).
 *
 */
#include <linux/interrupt.h>

#include <drm/drmP.h>
#include <drm/i915_drm.h>
#include "i915_drv.h"
#include "intel_mocs.h"

#define GEN9_LR_CONTEXT_RENDER_SIZE (22 * PAGE_SIZE)
#define GEN8_LR_CONTEXT_RENDER_SIZE (20 * PAGE_SIZE)
#define GEN8_LR_CONTEXT_OTHER_SIZE (2 * PAGE_SIZE)

#define RING_EXECLIST_QFULL             (1 << 0x2)
#define RING_EXECLIST1_VALID            (1 << 0x3)
#define RING_EXECLIST0_VALID            (1 << 0x4)
#define RING_EXECLIST_ACTIVE_STATUS     (3 << 0xE)
#define RING_EXECLIST1_ACTIVE           (1 << 0x11)
#define RING_EXECLIST0_ACTIVE           (1 << 0x12)

#define GEN8_CTX_STATUS_IDLE_ACTIVE     (1 << 0)
#define GEN8_CTX_STATUS_PREEMPTED       (1 << 1)
#define GEN8_CTX_STATUS_ELEMENT_SWITCH  (1 << 2)
#define GEN8_CTX_STATUS_ACTIVE_IDLE     (1 << 3)
#define GEN8_CTX_STATUS_COMPLETE        (1 << 4)
#define GEN8_CTX_STATUS_LITE_RESTORE    (1 << 15)

#define CTX_LRI_HEADER_0                0x01
#define CTX_CONTEXT_CONTROL             0x02
#define CTX_RING_HEAD                   0x04
#define CTX_RING_TAIL                   0x06
#define CTX_RING_BUFFER_START           0x08
#define CTX_RING_BUFFER_CONTROL         0x0a
#define CTX_BB_HEAD_U                   0x0c
#define CTX_BB_HEAD_L                   0x0e
#define CTX_BB_STATE                    0x10
#define CTX_SECOND_BB_HEAD_U            0x12
#define CTX_SECOND_BB_HEAD_L            0x14
#define CTX_SECOND_BB_STATE             0x16
#define CTX_BB_PER_CTX_PTR              0x18
#define CTX_RCS_INDIRECT_CTX            0x1a
#define CTX_RCS_INDIRECT_CTX_OFFSET     0x1c
#define CTX_LRI_HEADER_1                0x21
#define CTX_CTX_TIMESTAMP               0x22
#define CTX_PDP3_UDW                    0x24
#define CTX_PDP3_LDW                    0x26
#define CTX_PDP2_UDW                    0x28
#define CTX_PDP2_LDW                    0x2a
#define CTX_PDP1_UDW                    0x2c
#define CTX_PDP1_LDW                    0x2e
#define CTX_PDP0_UDW                    0x30
#define CTX_PDP0_LDW                    0x32
#define CTX_LRI_HEADER_2                0x41
#define CTX_R_PWR_CLK_STATE             0x42
#define CTX_GPGPU_CSR_BASE_ADDRESS      0x44

#define GEN8_CTX_VALID (1<<0)
#define GEN8_CTX_FORCE_PD_RESTORE (1<<1)
#define GEN8_CTX_FORCE_RESTORE (1<<2)
#define GEN8_CTX_L3LLC_COHERENT (1<<5)
#define GEN8_CTX_PRIVILEGE (1<<8)

#define ASSIGN_CTX_REG(reg_state, pos, reg, val) do { \
        (reg_state)[(pos)+0] = i915_mmio_reg_offset(reg); \
        (reg_state)[(pos)+1] = (val); \
} while (0)

#define ASSIGN_CTX_PDP(ppgtt, reg_state, n) do {                \
        const u64 _addr = i915_page_dir_dma_addr((ppgtt), (n)); \
        reg_state[CTX_PDP ## n ## _UDW+1] = upper_32_bits(_addr); \
        reg_state[CTX_PDP ## n ## _LDW+1] = lower_32_bits(_addr); \
} while (0)

#define ASSIGN_CTX_PML4(ppgtt, reg_state) do { \
        reg_state[CTX_PDP0_UDW + 1] = upper_32_bits(px_dma(&ppgtt->pml4)); \
        reg_state[CTX_PDP0_LDW + 1] = lower_32_bits(px_dma(&ppgtt->pml4)); \
} while (0)

enum {
        ADVANCED_CONTEXT = 0,
        LEGACY_32B_CONTEXT,
        ADVANCED_AD_CONTEXT,
        LEGACY_64B_CONTEXT
};
#define GEN8_CTX_ADDRESSING_MODE_SHIFT 3
#define GEN8_CTX_ADDRESSING_MODE(dev)  (USES_FULL_48BIT_PPGTT(dev) ?\
                LEGACY_64B_CONTEXT :\
                LEGACY_32B_CONTEXT)
enum {
        FAULT_AND_HANG = 0,
        FAULT_AND_HALT, /* Debug only */
        FAULT_AND_STREAM,
        FAULT_AND_CONTINUE /* Unsupported */
};
#define GEN8_CTX_ID_SHIFT 32
#define GEN8_CTX_ID_WIDTH 21
#define GEN8_CTX_RCS_INDIRECT_CTX_OFFSET_DEFAULT        0x17
#define GEN9_CTX_RCS_INDIRECT_CTX_OFFSET_DEFAULT        0x26

static int intel_lr_context_pin(struct intel_context *ctx,
                                struct intel_engine_cs *engine);

/**
 * intel_sanitize_enable_execlists() - sanitize i915.enable_execlists
 * @dev: DRM device.
 * @enable_execlists: value of i915.enable_execlists module parameter.
 *
 * Only certain platforms support Execlists (the prerequisites being
 * support for Logical Ring Contexts and Aliasing PPGTT or better).
 *
 * Return: 1 if Execlists is supported and has to be enabled.
 */
int intel_sanitize_enable_execlists(struct drm_device *dev, int enable_execlists)
{
        WARN_ON(i915.enable_ppgtt == -1);

        /* On platforms with execlist available, vGPU will only
         * support execlist mode, no ring buffer mode.
         */
        if (HAS_LOGICAL_RING_CONTEXTS(dev) && intel_vgpu_active(dev))
                return 1;

        if (INTEL_INFO(dev)->gen >= 9)
                return 1;

        if (enable_execlists == 0)
                return 0;

        if (HAS_LOGICAL_RING_CONTEXTS(dev) && USES_PPGTT(dev) &&
            i915.use_mmio_flip >= 0)
                return 1;

        return 0;
}

static void
logical_ring_init_platform_invariants(struct intel_engine_cs *engine)
{
        struct drm_device *dev = engine->dev;

        if (IS_GEN8(dev) || IS_GEN9(dev))
                engine->idle_lite_restore_wa = ~0;

        engine->disable_lite_restore_wa = (IS_SKL_REVID(dev, 0, SKL_REVID_B0) ||
                                        IS_BXT_REVID(dev, 0, BXT_REVID_A1)) &&
                                        (engine->id == VCS || engine->id == VCS2);

        engine->ctx_desc_template = GEN8_CTX_VALID;
        engine->ctx_desc_template |= GEN8_CTX_ADDRESSING_MODE(dev) <<
                                   GEN8_CTX_ADDRESSING_MODE_SHIFT;
        if (IS_GEN8(dev))
                engine->ctx_desc_template |= GEN8_CTX_L3LLC_COHERENT;
        engine->ctx_desc_template |= GEN8_CTX_PRIVILEGE;

        /* TODO: WaDisableLiteRestore when we start using semaphore
         * signalling between Command Streamers */
        /* ring->ctx_desc_template |= GEN8_CTX_FORCE_RESTORE; */

        /* WaEnableForceRestoreInCtxtDescForVCS:skl */
        /* WaEnableForceRestoreInCtxtDescForVCS:bxt */
        if (engine->disable_lite_restore_wa)
                engine->ctx_desc_template |= GEN8_CTX_FORCE_RESTORE;
}

/**
 * intel_lr_context_descriptor_update() - calculate & cache the descriptor
 *                                        descriptor for a pinned context
 *
 * @ctx: Context to work on
 * @ring: Engine the descriptor will be used with
 *
 * The context descriptor encodes various attributes of a context,
 * including its GTT address and some flags. Because it's fairly
 * expensive to calculate, we'll just do it once and cache the result,
 * which remains valid until the context is unpinned.
 *
 * This is what a descriptor looks like, from LSB to MSB:
 *    bits  0-11:    flags, GEN8_CTX_* (cached in ctx_desc_template)
 *    bits 12-31:    LRCA, GTT address of (the HWSP of) this context
 *    bits 32-52:    ctx ID, a globally unique tag
 *    bits 53-54:    mbz, reserved for use by hardware
 *    bits 55-63:    group ID, currently unused and set to 0
 */
static void
intel_lr_context_descriptor_update(struct intel_context *ctx,
                                   struct intel_engine_cs *engine)
{
        u64 desc;

        BUILD_BUG_ON(MAX_CONTEXT_HW_ID > (1<<GEN8_CTX_ID_WIDTH));

        desc = engine->ctx_desc_template;                       /* bits  0-11 */
        desc |= ctx->engine[engine->id].lrc_vma->node.start +   /* bits 12-31 */
               LRC_PPHWSP_PN * PAGE_SIZE;
        desc |= (u64)ctx->hw_id << GEN8_CTX_ID_SHIFT;           /* bits 32-52 */

        ctx->engine[engine->id].lrc_desc = desc;
}

uint64_t intel_lr_context_descriptor(struct intel_context *ctx,
                                     struct intel_engine_cs *engine)
{
        return ctx->engine[engine->id].lrc_desc;
}

static void execlists_elsp_write(struct drm_i915_gem_request *rq0,
                                 struct drm_i915_gem_request *rq1)
{

        struct intel_engine_cs *engine = rq0->engine;
        struct drm_device *dev = engine->dev;
        struct drm_i915_private *dev_priv = dev->dev_private;
        uint64_t desc[2];

        if (rq1) {
                desc[1] = intel_lr_context_descriptor(rq1->ctx, rq1->engine);
                rq1->elsp_submitted++;
        } else {
                desc[1] = 0;
        }

        desc[0] = intel_lr_context_descriptor(rq0->ctx, rq0->engine);
        rq0->elsp_submitted++;

        /* You must always write both descriptors in the order below. */
        I915_WRITE_FW(RING_ELSP(engine), upper_32_bits(desc[1]));
        I915_WRITE_FW(RING_ELSP(engine), lower_32_bits(desc[1]));

        I915_WRITE_FW(RING_ELSP(engine), upper_32_bits(desc[0]));
        /* The context is automatically loaded after the following */
        I915_WRITE_FW(RING_ELSP(engine), lower_32_bits(desc[0]));

        /* ELSP is a wo register, use another nearby reg for posting */
        POSTING_READ_FW(RING_EXECLIST_STATUS_LO(engine));
}

static void
execlists_update_context_pdps(struct i915_hw_ppgtt *ppgtt, u32 *reg_state)
{
        ASSIGN_CTX_PDP(ppgtt, reg_state, 3);
        ASSIGN_CTX_PDP(ppgtt, reg_state, 2);
        ASSIGN_CTX_PDP(ppgtt, reg_state, 1);
        ASSIGN_CTX_PDP(ppgtt, reg_state, 0);
}

static void execlists_update_context(struct drm_i915_gem_request *rq)
{
        struct intel_engine_cs *engine = rq->engine;
        struct i915_hw_ppgtt *ppgtt = rq->ctx->ppgtt;
        uint32_t *reg_state = rq->ctx->engine[engine->id].lrc_reg_state;

        reg_state[CTX_RING_TAIL+1] = rq->tail;

        /* True 32b PPGTT with dynamic page allocation: update PDP
         * registers and point the unallocated PDPs to scratch page.
         * PML4 is allocated during ppgtt init, so this is not needed
         * in 48-bit mode.
         */
        if (ppgtt && !USES_FULL_48BIT_PPGTT(ppgtt->base.dev))
                execlists_update_context_pdps(ppgtt, reg_state);
}

static void execlists_submit_requests(struct drm_i915_gem_request *rq0,
                                      struct drm_i915_gem_request *rq1)
{
        struct drm_i915_private *dev_priv = rq0->i915;
        unsigned int fw_domains = rq0->engine->fw_domains;

        execlists_update_context(rq0);

        if (rq1)
                execlists_update_context(rq1);

        spin_lock_irq(&dev_priv->uncore.lock);
        intel_uncore_forcewake_get__locked(dev_priv, fw_domains);

        execlists_elsp_write(rq0, rq1);

        intel_uncore_forcewake_put__locked(dev_priv, fw_domains);
        spin_unlock_irq(&dev_priv->uncore.lock);
}

static void execlists_context_unqueue(struct intel_engine_cs *engine)
{
        struct drm_i915_gem_request *req0 = NULL, *req1 = NULL;
        struct drm_i915_gem_request *cursor, *tmp;

        assert_spin_locked(&engine->execlist_lock);

        /*
         * If irqs are not active generate a warning as batches that finish
         * without the irqs may get lost and a GPU Hang may occur.
         */
        WARN_ON(!intel_irqs_enabled(engine->dev->dev_private));

        /* Try to read in pairs */
        list_for_each_entry_safe(cursor, tmp, &engine->execlist_queue,
                                 execlist_link) {
                if (!req0) {
                        req0 = cursor;
                } else if (req0->ctx == cursor->ctx) {
                        /* Same ctx: ignore first request, as second request
                         * will update tail past first request's workload */
                        cursor->elsp_submitted = req0->elsp_submitted;
                        list_move_tail(&req0->execlist_link,
                                       &engine->execlist_retired_req_list);
                        req0 = cursor;
                } else {
                        req1 = cursor;
                        WARN_ON(req1->elsp_submitted);
                        break;
                }
        }

        if (unlikely(!req0))
                return;

        if (req0->elsp_submitted & engine->idle_lite_restore_wa) {
                /*
                 * WaIdleLiteRestore: make sure we never cause a lite restore
                 * with HEAD==TAIL.
                 *
                 * Apply the wa NOOPS to prevent ring:HEAD == req:TAIL as we
                 * resubmit the request. See gen8_emit_request() for where we
                 * prepare the padding after the end of the request.
                 */
                struct intel_ringbuffer *ringbuf;

                ringbuf = req0->ctx->engine[engine->id].ringbuf;
                req0->tail += 8;
                req0->tail &= ringbuf->size - 1;
        }

        execlists_submit_requests(req0, req1);
}

static unsigned int
execlists_check_remove_request(struct intel_engine_cs *engine, u32 request_id)
{
        struct drm_i915_gem_request *head_req;

        assert_spin_locked(&engine->execlist_lock);

        head_req = list_first_entry_or_null(&engine->execlist_queue,
                                            struct drm_i915_gem_request,
                                            execlist_link);

        if (!head_req)
                return 0;

        if (unlikely(head_req->ctx->hw_id != request_id))
                return 0;

        WARN(head_req->elsp_submitted == 0, "Never submitted head request\n");

        if (--head_req->elsp_submitted > 0)
                return 0;

        list_move_tail(&head_req->execlist_link,
                       &engine->execlist_retired_req_list);

        return 1;
}

static u32
get_context_status(struct intel_engine_cs *engine, unsigned int read_pointer,
                   u32 *context_id)
{
        struct drm_i915_private *dev_priv = engine->dev->dev_private;
        u32 status;

        read_pointer %= GEN8_CSB_ENTRIES;

        status = I915_READ_FW(RING_CONTEXT_STATUS_BUF_LO(engine, read_pointer));

        if (status & GEN8_CTX_STATUS_IDLE_ACTIVE)
                return 0;

        *context_id = I915_READ_FW(RING_CONTEXT_STATUS_BUF_HI(engine,
                                                              read_pointer));

        return status;
}

/**
 * intel_lrc_irq_handler() - handle Context Switch interrupts
 * @engine: Engine Command Streamer to handle.
 *
 * Check the unread Context Status Buffers and manage the submission of new
 * contexts to the ELSP accordingly.
 */
static void intel_lrc_irq_handler(unsigned long data)
{
        struct intel_engine_cs *engine = (struct intel_engine_cs *)data;
        struct drm_i915_private *dev_priv = engine->dev->dev_private;
        u32 status_pointer;
        unsigned int read_pointer, write_pointer;
        u32 csb[GEN8_CSB_ENTRIES][2];
        unsigned int csb_read = 0, i;
        unsigned int submit_contexts = 0;

        intel_uncore_forcewake_get(dev_priv, engine->fw_domains);

        status_pointer = I915_READ_FW(RING_CONTEXT_STATUS_PTR(engine));

        read_pointer = engine->next_context_status_buffer;
        write_pointer = GEN8_CSB_WRITE_PTR(status_pointer);
        if (read_pointer > write_pointer)
                write_pointer += GEN8_CSB_ENTRIES;

        while (read_pointer < write_pointer) {
                if (WARN_ON_ONCE(csb_read == GEN8_CSB_ENTRIES))
                        break;
                csb[csb_read][0] = get_context_status(engine, ++read_pointer,
                                                      &csb[csb_read][1]);
                csb_read++;
        }

        engine->next_context_status_buffer = write_pointer % GEN8_CSB_ENTRIES;

        /* Update the read pointer to the old write pointer. Manual ringbuffer
         * management ftw </sarcasm> */
        I915_WRITE_FW(RING_CONTEXT_STATUS_PTR(engine),
                      _MASKED_FIELD(GEN8_CSB_READ_PTR_MASK,
                                    engine->next_context_status_buffer << 8));

        intel_uncore_forcewake_put(dev_priv, engine->fw_domains);

        spin_lock(&engine->execlist_lock);

        for (i = 0; i < csb_read; i++) {
                if (unlikely(csb[i][0] & GEN8_CTX_STATUS_PREEMPTED)) {
                        if (csb[i][0] & GEN8_CTX_STATUS_LITE_RESTORE) {
                                if (execlists_check_remove_request(engine, csb[i][1]))
                                        WARN(1, "Lite Restored request removed from queue\n");
                        } else
                                WARN(1, "Preemption without Lite Restore\n");
                }

                if (csb[i][0] & (GEN8_CTX_STATUS_ACTIVE_IDLE |
                    GEN8_CTX_STATUS_ELEMENT_SWITCH))
                        submit_contexts +=
                                execlists_check_remove_request(engine, csb[i][1]);
        }

        if (submit_contexts) {
                if (!engine->disable_lite_restore_wa ||
                    (csb[i][0] & GEN8_CTX_STATUS_ACTIVE_IDLE))
                        execlists_context_unqueue(engine);
        }

        spin_unlock(&engine->execlist_lock);

        if (unlikely(submit_contexts > 2))
                DRM_ERROR("More than two context complete events?\n");
}

static void execlists_context_queue(struct drm_i915_gem_request *request)
{
        struct intel_engine_cs *engine = request->engine;
        struct drm_i915_gem_request *cursor;
        int num_elements = 0;

        if (request->ctx != request->i915->kernel_context)
                intel_lr_context_pin(request->ctx, engine);

        i915_gem_request_reference(request);

        spin_lock_bh(&engine->execlist_lock);

        list_for_each_entry(cursor, &engine->execlist_queue, execlist_link)
                if (++num_elements > 2)
                        break;

        if (num_elements > 2) {
                struct drm_i915_gem_request *tail_req;

                tail_req = list_last_entry(&engine->execlist_queue,
                                           struct drm_i915_gem_request,
                                           execlist_link);

                if (request->ctx == tail_req->ctx) {
                        WARN(tail_req->elsp_submitted != 0,
                                "More than 2 already-submitted reqs queued\n");
                        list_move_tail(&tail_req->execlist_link,
                                       &engine->execlist_retired_req_list);
                }
        }

        list_add_tail(&request->execlist_link, &engine->execlist_queue);
        if (num_elements == 0)
                execlists_context_unqueue(engine);

        spin_unlock_bh(&engine->execlist_lock);
}

static int logical_ring_invalidate_all_caches(struct drm_i915_gem_request *req)
{
        struct intel_engine_cs *engine = req->engine;
        uint32_t flush_domains;
        int ret;

        flush_domains = 0;
        if (engine->gpu_caches_dirty)
                flush_domains = I915_GEM_GPU_DOMAINS;

        ret = engine->emit_flush(req, I915_GEM_GPU_DOMAINS, flush_domains);
        if (ret)
                return ret;

        engine->gpu_caches_dirty = false;
        return 0;
}

static int execlists_move_to_gpu(struct drm_i915_gem_request *req,
                                 struct list_head *vmas)
{
        const unsigned other_rings = ~intel_engine_flag(req->engine);
        struct i915_vma *vma;
        uint32_t flush_domains = 0;
        bool flush_chipset = false;
        int ret;

        list_for_each_entry(vma, vmas, exec_list) {
                struct drm_i915_gem_object *obj = vma->obj;

                if (obj->active & other_rings) {
                        ret = i915_gem_object_sync(obj, req->engine, &req);
                        if (ret)
                                return ret;
                }

                if (obj->base.write_domain & I915_GEM_DOMAIN_CPU)
                        flush_chipset |= i915_gem_clflush_object(obj, false);

                flush_domains |= obj->base.write_domain;
        }

        if (flush_domains & I915_GEM_DOMAIN_GTT)
                wmb();

        /* Unconditionally invalidate gpu caches and ensure that we do flush
         * any residual writes from the previous batch.
         */
        return logical_ring_invalidate_all_caches(req);
}

int intel_logical_ring_alloc_request_extras(struct drm_i915_gem_request *request)
{
        int ret;

        /* Flush enough space to reduce the likelihood of waiting after
         * we start building the request - in which case we will just
         * have to repeat work.
         */
        request->reserved_space += MIN_SPACE_FOR_ADD_REQUEST;

        request->ringbuf = request->ctx->engine[request->engine->id].ringbuf;

        if (i915.enable_guc_submission) {
                /*
                 * Check that the GuC has space for the request before
                 * going any further, as the i915_add_request() call
                 * later on mustn't fail ...
                 */
                struct intel_guc *guc = &request->i915->guc;

                ret = i915_guc_wq_check_space(guc->execbuf_client);
                if (ret)
                        return ret;
        }

        if (request->ctx != request->i915->kernel_context) {
                ret = intel_lr_context_pin(request->ctx, request->engine);
                if (ret)
                        return ret;
        }

        ret = intel_ring_begin(request, 0);
        if (ret)
                goto err_unpin;

        request->reserved_space -= MIN_SPACE_FOR_ADD_REQUEST;
        return 0;

err_unpin:
        if (request->ctx != request->i915->kernel_context)
                intel_lr_context_unpin(request->ctx, request->engine);
        return ret;
}

/*
 * intel_logical_ring_advance_and_submit() - advance the tail and submit the workload
 * @request: Request to advance the logical ringbuffer of.
 *
 * The tail is updated in our logical ringbuffer struct, not in the actual context. What
 * really happens during submission is that the context and current tail will be placed
 * on a queue waiting for the ELSP to be ready to accept a new context submission. At that
 * point, the tail *inside* the context is updated and the ELSP written to.
 */
static int
intel_logical_ring_advance_and_submit(struct drm_i915_gem_request *request)
{
        struct intel_ringbuffer *ringbuf = request->ringbuf;
        struct drm_i915_private *dev_priv = request->i915;
        struct intel_engine_cs *engine = request->engine;

        intel_logical_ring_advance(ringbuf);
        request->tail = ringbuf->tail;

        /*
         * Here we add two extra NOOPs as padding to avoid
         * lite restore of a context with HEAD==TAIL.
         *
         * Caller must reserve WA_TAIL_DWORDS for us!
         */
        intel_logical_ring_emit(ringbuf, MI_NOOP);
        intel_logical_ring_emit(ringbuf, MI_NOOP);
        intel_logical_ring_advance(ringbuf);

        if (intel_engine_stopped(engine))
                return 0;

        if (engine->last_context != request->ctx) {
                if (engine->last_context)
                        intel_lr_context_unpin(engine->last_context, engine);
                if (request->ctx != request->i915->kernel_context) {
                        intel_lr_context_pin(request->ctx, engine);
                        engine->last_context = request->ctx;
                } else {
                        engine->last_context = NULL;
                }
        }

        if (dev_priv->guc.execbuf_client)
                i915_guc_submit(dev_priv->guc.execbuf_client, request);
        else
                execlists_context_queue(request);

        return 0;
}

/**
 * execlists_submission() - submit a batchbuffer for execution, Execlists style
 * @dev: DRM device.
 * @file: DRM file.
 * @ring: Engine Command Streamer to submit to.
 * @ctx: Context to employ for this submission.
 * @args: execbuffer call arguments.
 * @vmas: list of vmas.
 * @batch_obj: the batchbuffer to submit.
 * @exec_start: batchbuffer start virtual address pointer.
 * @dispatch_flags: translated execbuffer call flags.
 *
 * This is the evil twin version of i915_gem_ringbuffer_submission. It abstracts
 * away the submission details of the execbuffer ioctl call.
 *
 * Return: non-zero if the submission fails.
 */
int intel_execlists_submission(struct i915_execbuffer_params *params,
                               struct drm_i915_gem_execbuffer2 *args,
                               struct list_head *vmas)
{
        struct drm_device       *dev = params->dev;
        struct intel_engine_cs *engine = params->engine;
        struct drm_i915_private *dev_priv = dev->dev_private;
        struct intel_ringbuffer *ringbuf = params->ctx->engine[engine->id].ringbuf;
        u64 exec_start;
        int instp_mode;
        u32 instp_mask;
        int ret;

        instp_mode = args->flags & I915_EXEC_CONSTANTS_MASK;
        instp_mask = I915_EXEC_CONSTANTS_MASK;
        switch (instp_mode) {
        case I915_EXEC_CONSTANTS_REL_GENERAL:
        case I915_EXEC_CONSTANTS_ABSOLUTE:
        case I915_EXEC_CONSTANTS_REL_SURFACE:
                if (instp_mode != 0 && engine != &dev_priv->engine[RCS]) {
                        DRM_DEBUG("non-0 rel constants mode on non-RCS\n");
                        return -EINVAL;
                }

                if (instp_mode != dev_priv->relative_constants_mode) {
                        if (instp_mode == I915_EXEC_CONSTANTS_REL_SURFACE) {
                                DRM_DEBUG("rel surface constants mode invalid on gen5+\n");
                                return -EINVAL;
                        }

                        /* The HW changed the meaning on this bit on gen6 */
                        instp_mask &= ~I915_EXEC_CONSTANTS_REL_SURFACE;
                }
                break;
        default:
                DRM_DEBUG("execbuf with unknown constants: %d\n", instp_mode);
                return -EINVAL;
        }

        if (args->flags & I915_EXEC_GEN7_SOL_RESET) {
                DRM_DEBUG("sol reset is gen7 only\n");
                return -EINVAL;
        }

        ret = execlists_move_to_gpu(params->request, vmas);
        if (ret)
                return ret;

        if (engine == &dev_priv->engine[RCS] &&
            instp_mode != dev_priv->relative_constants_mode) {
                ret = intel_ring_begin(params->request, 4);
                if (ret)
                        return ret;

                intel_logical_ring_emit(ringbuf, MI_NOOP);
                intel_logical_ring_emit(ringbuf, MI_LOAD_REGISTER_IMM(1));
                intel_logical_ring_emit_reg(ringbuf, INSTPM);
                intel_logical_ring_emit(ringbuf, instp_mask << 16 | instp_mode);
                intel_logical_ring_advance(ringbuf);

                dev_priv->relative_constants_mode = instp_mode;
        }

        exec_start = params->batch_obj_vm_offset +
                     args->batch_start_offset;

        ret = engine->emit_bb_start(params->request, exec_start, params->dispatch_flags);
        if (ret)
                return ret;

        trace_i915_gem_ring_dispatch(params->request, params->dispatch_flags);

        i915_gem_execbuffer_move_to_active(vmas, params->request);

        return 0;
}

void intel_execlists_retire_requests(struct intel_engine_cs *engine)
{
        struct drm_i915_gem_request *req, *tmp;
        struct list_head retired_list;

        WARN_ON(!mutex_is_locked(&engine->dev->struct_mutex));
        if (list_empty(&engine->execlist_retired_req_list))
                return;

        INIT_LIST_HEAD(&retired_list);
        spin_lock_bh(&engine->execlist_lock);
        list_replace_init(&engine->execlist_retired_req_list, &retired_list);
        spin_unlock_bh(&engine->execlist_lock);

        list_for_each_entry_safe(req, tmp, &retired_list, execlist_link) {
                struct intel_context *ctx = req->ctx;
                struct drm_i915_gem_object *ctx_obj =
                                ctx->engine[engine->id].state;

                if (ctx_obj && (ctx != req->i915->kernel_context))
                        intel_lr_context_unpin(ctx, engine);

                list_del(&req->execlist_link);
                i915_gem_request_unreference(req);
        }
}

void intel_logical_ring_stop(struct intel_engine_cs *engine)
{
        struct drm_i915_private *dev_priv = engine->dev->dev_private;
        int ret;

        if (!intel_engine_initialized(engine))
                return;

        ret = intel_engine_idle(engine);
        if (ret)
                DRM_ERROR("failed to quiesce %s whilst cleaning up: %d\n",
                          engine->name, ret);

        /* TODO: Is this correct with Execlists enabled? */
        I915_WRITE_MODE(engine, _MASKED_BIT_ENABLE(STOP_RING));
        if (wait_for((I915_READ_MODE(engine) & MODE_IDLE) != 0, 1000)) {
                DRM_ERROR("%s :timed out trying to stop ring\n", engine->name);
                return;
        }
        I915_WRITE_MODE(engine, _MASKED_BIT_DISABLE(STOP_RING));
}

int logical_ring_flush_all_caches(struct drm_i915_gem_request *req)
{
        struct intel_engine_cs *engine = req->engine;
        int ret;

        if (!engine->gpu_caches_dirty)
                return 0;

        ret = engine->emit_flush(req, 0, I915_GEM_GPU_DOMAINS);
        if (ret)
                return ret;

        engine->gpu_caches_dirty = false;
        return 0;
}

static int intel_lr_context_do_pin(struct intel_context *ctx,
                                   struct intel_engine_cs *engine)
{
        struct drm_device *dev = engine->dev;
        struct drm_i915_private *dev_priv = dev->dev_private;
        struct drm_i915_gem_object *ctx_obj = ctx->engine[engine->id].state;
        struct intel_ringbuffer *ringbuf = ctx->engine[engine->id].ringbuf;
        void *vaddr;
        u32 *lrc_reg_state;
        int ret;

        WARN_ON(!mutex_is_locked(&engine->dev->struct_mutex));

        ret = i915_gem_obj_ggtt_pin(ctx_obj, GEN8_LR_CONTEXT_ALIGN,
                        PIN_OFFSET_BIAS | GUC_WOPCM_TOP);
        if (ret)
                return ret;

        vaddr = i915_gem_object_pin_map(ctx_obj);
        if (IS_ERR(vaddr)) {
                ret = PTR_ERR(vaddr);
                goto unpin_ctx_obj;
        }

        lrc_reg_state = vaddr + LRC_STATE_PN * PAGE_SIZE;

        ret = intel_pin_and_map_ringbuffer_obj(engine->dev, ringbuf);
        if (ret)
                goto unpin_map;

        ctx->engine[engine->id].lrc_vma = i915_gem_obj_to_ggtt(ctx_obj);
        intel_lr_context_descriptor_update(ctx, engine);
        lrc_reg_state[CTX_RING_BUFFER_START+1] = ringbuf->vma->node.start;
        ctx->engine[engine->id].lrc_reg_state = lrc_reg_state;
        ctx_obj->dirty = true;

        /* Invalidate GuC TLB. */
        if (i915.enable_guc_submission)
                I915_WRITE(GEN8_GTCR, GEN8_GTCR_INVALIDATE);

        return ret;

unpin_map:
        i915_gem_object_unpin_map(ctx_obj);
unpin_ctx_obj:
        i915_gem_object_ggtt_unpin(ctx_obj);

        return ret;
}

static int intel_lr_context_pin(struct intel_context *ctx,
                                struct intel_engine_cs *engine)
{
        int ret = 0;

        if (ctx->engine[engine->id].pin_count++ == 0) {
                ret = intel_lr_context_do_pin(ctx, engine);
                if (ret)
                        goto reset_pin_count;

                i915_gem_context_reference(ctx);
        }
        return ret;

reset_pin_count:
        ctx->engine[engine->id].pin_count = 0;
        return ret;
}

void intel_lr_context_unpin(struct intel_context *ctx,
                            struct intel_engine_cs *engine)
{
        struct drm_i915_gem_object *ctx_obj = ctx->engine[engine->id].state;

        WARN_ON(!mutex_is_locked(&ctx->i915->dev->struct_mutex));
        if (--ctx->engine[engine->id].pin_count == 0) {
                i915_gem_object_unpin_map(ctx_obj);
                intel_unpin_ringbuffer_obj(ctx->engine[engine->id].ringbuf);
                i915_gem_object_ggtt_unpin(ctx_obj);
                ctx->engine[engine->id].lrc_vma = NULL;
                ctx->engine[engine->id].lrc_desc = 0;
                ctx->engine[engine->id].lrc_reg_state = NULL;

                i915_gem_context_unreference(ctx);
        }
}

static int intel_logical_ring_workarounds_emit(struct drm_i915_gem_request *req)
{
        int ret, i;
        struct intel_engine_cs *engine = req->engine;
        struct intel_ringbuffer *ringbuf = req->ringbuf;
        struct drm_device *dev = engine->dev;
        struct drm_i915_private *dev_priv = dev->dev_private;
        struct i915_workarounds *w = &dev_priv->workarounds;

        if (w->count == 0)
                return 0;

        engine->gpu_caches_dirty = true;
        ret = logical_ring_flush_all_caches(req);
        if (ret)
                return ret;

        ret = intel_ring_begin(req, w->count * 2 + 2);
        if (ret)
                return ret;

        intel_logical_ring_emit(ringbuf, MI_LOAD_REGISTER_IMM(w->count));
        for (i = 0; i < w->count; i++) {
                intel_logical_ring_emit_reg(ringbuf, w->reg[i].addr);
                intel_logical_ring_emit(ringbuf, w->reg[i].value);
        }
        intel_logical_ring_emit(ringbuf, MI_NOOP);

        intel_logical_ring_advance(ringbuf);

        engine->gpu_caches_dirty = true;
        ret = logical_ring_flush_all_caches(req);
        if (ret)
                return ret;

        return 0;
}

#define wa_ctx_emit(batch, index, cmd)                                  \
        do {                                                            \
                int __index = (index)++;                                \
                if (WARN_ON(__index >= (PAGE_SIZE / sizeof(uint32_t)))) { \
                        return -ENOSPC;                                 \
                }                                                       \
                batch[__index] = (cmd);                                 \
        } while (0)

#define wa_ctx_emit_reg(batch, index, reg) \
        wa_ctx_emit((batch), (index), i915_mmio_reg_offset(reg))

/*
 * In this WA we need to set GEN8_L3SQCREG4[21:21] and reset it after
 * PIPE_CONTROL instruction. This is required for the flush to happen correctly
 * but there is a slight complication as this is applied in WA batch where the
 * values are only initialized once so we cannot take register value at the
 * beginning and reuse it further; hence we save its value to memory, upload a
 * constant value with bit21 set and then we restore it back with the saved value.
 * To simplify the WA, a constant value is formed by using the default value
 * of this register. This shouldn't be a problem because we are only modifying
 * it for a short period and this batch in non-premptible. We can ofcourse
 * use additional instructions that read the actual value of the register
 * at that time and set our bit of interest but it makes the WA complicated.
 *
 * This WA is also required for Gen9 so extracting as a function avoids
 * code duplication.
 */
static inline int gen8_emit_flush_coherentl3_wa(struct intel_engine_cs *engine,
                                                uint32_t *const batch,
                                                uint32_t index)
{
        uint32_t l3sqc4_flush = (0x40400000 | GEN8_LQSC_FLUSH_COHERENT_LINES);

        /*
         * WaDisableLSQCROPERFforOCL:skl
         * This WA is implemented in skl_init_clock_gating() but since
         * this batch updates GEN8_L3SQCREG4 with default value we need to
         * set this bit here to retain the WA during flush.
         */
        if (IS_SKL_REVID(engine->dev, 0, SKL_REVID_E0))
                l3sqc4_flush |= GEN8_LQSC_RO_PERF_DIS;

        wa_ctx_emit(batch, index, (MI_STORE_REGISTER_MEM_GEN8 |
                                   MI_SRM_LRM_GLOBAL_GTT));
        wa_ctx_emit_reg(batch, index, GEN8_L3SQCREG4);
        wa_ctx_emit(batch, index, engine->scratch.gtt_offset + 256);
        wa_ctx_emit(batch, index, 0);

        wa_ctx_emit(batch, index, MI_LOAD_REGISTER_IMM(1));
        wa_ctx_emit_reg(batch, index, GEN8_L3SQCREG4);
        wa_ctx_emit(batch, index, l3sqc4_flush);

        wa_ctx_emit(batch, index, GFX_OP_PIPE_CONTROL(6));
        wa_ctx_emit(batch, index, (PIPE_CONTROL_CS_STALL |
                                   PIPE_CONTROL_DC_FLUSH_ENABLE));
        wa_ctx_emit(batch, index, 0);
        wa_ctx_emit(batch, index, 0);
        wa_ctx_emit(batch, index, 0);
        wa_ctx_emit(batch, index, 0);

        wa_ctx_emit(batch, index, (MI_LOAD_REGISTER_MEM_GEN8 |
                                   MI_SRM_LRM_GLOBAL_GTT));
        wa_ctx_emit_reg(batch, index, GEN8_L3SQCREG4);
        wa_ctx_emit(batch, index, engine->scratch.gtt_offset + 256);
        wa_ctx_emit(batch, index, 0);

        return index;
}

static inline uint32_t wa_ctx_start(struct i915_wa_ctx_bb *wa_ctx,
                                    uint32_t offset,
                                    uint32_t start_alignment)
{
        return wa_ctx->offset = ALIGN(offset, start_alignment);
}

static inline int wa_ctx_end(struct i915_wa_ctx_bb *wa_ctx,
                             uint32_t offset,
                             uint32_t size_alignment)
{
        wa_ctx->size = offset - wa_ctx->offset;

        WARN(wa_ctx->size % size_alignment,
             "wa_ctx_bb failed sanity checks: size %d is not aligned to %d\n",
             wa_ctx->size, size_alignment);
        return 0;
}

/**
 * gen8_init_indirectctx_bb() - initialize indirect ctx batch with WA
 *
 * @ring: only applicable for RCS
 * @wa_ctx: structure representing wa_ctx
 *  offset: specifies start of the batch, should be cache-aligned. This is updated
 *    with the offset value received as input.
 *  size: size of the batch in DWORDS but HW expects in terms of cachelines
 * @batch: page in which WA are loaded
 * @offset: This field specifies the start of the batch, it should be
 *  cache-aligned otherwise it is adjusted accordingly.
 *  Typically we only have one indirect_ctx and per_ctx batch buffer which are
 *  initialized at the beginning and shared across all contexts but this field
 *  helps us to have multiple batches at different offsets and select them based
 *  on a criteria. At the moment this batch always start at the beginning of the page
 *  and at this point we don't have multiple wa_ctx batch buffers.
 *
 *  The number of WA applied are not known at the beginning; we use this field
 *  to return the no of DWORDS written.
 *
 *  It is to be noted that this batch does not contain MI_BATCH_BUFFER_END
 *  so it adds NOOPs as padding to make it cacheline aligned.
 *  MI_BATCH_BUFFER_END will be added to perctx batch and both of them together
 *  makes a complete batch buffer.
 *
 * Return: non-zero if we exceed the PAGE_SIZE limit.
 */

static int gen8_init_indirectctx_bb(struct intel_engine_cs *engine,
                                    struct i915_wa_ctx_bb *wa_ctx,
                                    uint32_t *const batch,
                                    uint32_t *offset)
{
        uint32_t scratch_addr;
        uint32_t index = wa_ctx_start(wa_ctx, *offset, CACHELINE_DWORDS);

        /* WaDisableCtxRestoreArbitration:bdw,chv */
        wa_ctx_emit(batch, index, MI_ARB_ON_OFF | MI_ARB_DISABLE);

        /* WaFlushCoherentL3CacheLinesAtContextSwitch:bdw */
        if (IS_BROADWELL(engine->dev)) {
                int rc = gen8_emit_flush_coherentl3_wa(engine, batch, index);
                if (rc < 0)
                        return rc;
                index = rc;
        }

        /* WaClearSlmSpaceAtContextSwitch:bdw,chv */
        /* Actual scratch location is at 128 bytes offset */
        scratch_addr = engine->scratch.gtt_offset + 2*CACHELINE_BYTES;

        wa_ctx_emit(batch, index, GFX_OP_PIPE_CONTROL(6));
        wa_ctx_emit(batch, index, (PIPE_CONTROL_FLUSH_L3 |
                                   PIPE_CONTROL_GLOBAL_GTT_IVB |
                                   PIPE_CONTROL_CS_STALL |
                                   PIPE_CONTROL_QW_WRITE));
        wa_ctx_emit(batch, index, scratch_addr);
        wa_ctx_emit(batch, index, 0);
        wa_ctx_emit(batch, index, 0);
        wa_ctx_emit(batch, index, 0);

        /* Pad to end of cacheline */
        while (index % CACHELINE_DWORDS)
                wa_ctx_emit(batch, index, MI_NOOP);

        /*
         * MI_BATCH_BUFFER_END is not required in Indirect ctx BB because
         * execution depends on the length specified in terms of cache lines
         * in the register CTX_RCS_INDIRECT_CTX
         */

        return wa_ctx_end(wa_ctx, *offset = index, CACHELINE_DWORDS);
}

/**
 * gen8_init_perctx_bb() - initialize per ctx batch with WA
 *
 * @ring: only applicable for RCS
 * @wa_ctx: structure representing wa_ctx
 *  offset: specifies start of the batch, should be cache-aligned.
 *  size: size of the batch in DWORDS but HW expects in terms of cachelines
 * @batch: page in which WA are loaded
 * @offset: This field specifies the start of this batch.
 *   This batch is started immediately after indirect_ctx batch. Since we ensure
 *   that indirect_ctx ends on a cacheline this batch is aligned automatically.
 *
 *   The number of DWORDS written are returned using this field.
 *
 *  This batch is terminated with MI_BATCH_BUFFER_END and so we need not add padding
 *  to align it with cacheline as padding after MI_BATCH_BUFFER_END is redundant.
 */
static int gen8_init_perctx_bb(struct intel_engine_cs *engine,
                               struct i915_wa_ctx_bb *wa_ctx,
                               uint32_t *const batch,
                               uint32_t *offset)
{
        uint32_t index = wa_ctx_start(wa_ctx, *offset, CACHELINE_DWORDS);

        /* WaDisableCtxRestoreArbitration:bdw,chv */
        wa_ctx_emit(batch, index, MI_ARB_ON_OFF | MI_ARB_ENABLE);

        wa_ctx_emit(batch, index, MI_BATCH_BUFFER_END);

        return wa_ctx_end(wa_ctx, *offset = index, 1);
}

static int gen9_init_indirectctx_bb(struct intel_engine_cs *engine,
                                    struct i915_wa_ctx_bb *wa_ctx,
                                    uint32_t *const batch,
                                    uint32_t *offset)
{
        int ret;
        struct drm_device *dev = engine->dev;
        uint32_t index = wa_ctx_start(wa_ctx, *offset, CACHELINE_DWORDS);

        /* WaDisableCtxRestoreArbitration:skl,bxt */
        if (IS_SKL_REVID(dev, 0, SKL_REVID_D0) ||
            IS_BXT_REVID(dev, 0, BXT_REVID_A1))
                wa_ctx_emit(batch, index, MI_ARB_ON_OFF | MI_ARB_DISABLE);

        /* WaFlushCoherentL3CacheLinesAtContextSwitch:skl,bxt */
        ret = gen8_emit_flush_coherentl3_wa(engine, batch, index);
        if (ret < 0)
                return ret;
        index = ret;

        /* Pad to end of cacheline */
        while (index % CACHELINE_DWORDS)
                wa_ctx_emit(batch, index, MI_NOOP);

        return wa_ctx_end(wa_ctx, *offset = index, CACHELINE_DWORDS);
}

static int gen9_init_perctx_bb(struct intel_engine_cs *engine,
                               struct i915_wa_ctx_bb *wa_ctx,
                               uint32_t *const batch,
                               uint32_t *offset)
{
        struct drm_device *dev = engine->dev;
        uint32_t index = wa_ctx_start(wa_ctx, *offset, CACHELINE_DWORDS);

        /* WaSetDisablePixMaskCammingAndRhwoInCommonSliceChicken:skl,bxt */
        if (IS_SKL_REVID(dev, 0, SKL_REVID_B0) ||
            IS_BXT_REVID(dev, 0, BXT_REVID_A1)) {
                wa_ctx_emit(batch, index, MI_LOAD_REGISTER_IMM(1));
                wa_ctx_emit_reg(batch, index, GEN9_SLICE_COMMON_ECO_CHICKEN0);
                wa_ctx_emit(batch, index,
                            _MASKED_BIT_ENABLE(DISABLE_PIXEL_MASK_CAMMING));
                wa_ctx_emit(batch, index, MI_NOOP);
        }

        /* WaClearTdlStateAckDirtyBits:bxt */
        if (IS_BXT_REVID(dev, 0, BXT_REVID_B0)) {
                wa_ctx_emit(batch, index, MI_LOAD_REGISTER_IMM(4));

                wa_ctx_emit_reg(batch, index, GEN8_STATE_ACK);
                wa_ctx_emit(batch, index, _MASKED_BIT_DISABLE(GEN9_SUBSLICE_TDL_ACK_BITS));

                wa_ctx_emit_reg(batch, index, GEN9_STATE_ACK_SLICE1);
                wa_ctx_emit(batch, index, _MASKED_BIT_DISABLE(GEN9_SUBSLICE_TDL_ACK_BITS));

                wa_ctx_emit_reg(batch, index, GEN9_STATE_ACK_SLICE2);
                wa_ctx_emit(batch, index, _MASKED_BIT_DISABLE(GEN9_SUBSLICE_TDL_ACK_BITS));

                wa_ctx_emit_reg(batch, index, GEN7_ROW_CHICKEN2);
                /* dummy write to CS, mask bits are 0 to ensure the register is not modified */
                wa_ctx_emit(batch, index, 0x0);
                wa_ctx_emit(batch, index, MI_NOOP);
        }

        /* WaDisableCtxRestoreArbitration:skl,bxt */
        if (IS_SKL_REVID(dev, 0, SKL_REVID_D0) ||
            IS_BXT_REVID(dev, 0, BXT_REVID_A1))
                wa_ctx_emit(batch, index, MI_ARB_ON_OFF | MI_ARB_ENABLE);

        wa_ctx_emit(batch, index, MI_BATCH_BUFFER_END);

        return wa_ctx_end(wa_ctx, *offset = index, 1);
}

static int lrc_setup_wa_ctx_obj(struct intel_engine_cs *engine, u32 size)
{
        int ret;

        engine->wa_ctx.obj = i915_gem_object_create(engine->dev,
                                                   PAGE_ALIGN(size));
        if (IS_ERR(engine->wa_ctx.obj)) {
                DRM_DEBUG_DRIVER("alloc LRC WA ctx backing obj failed.\n");
                ret = PTR_ERR(engine->wa_ctx.obj);
                engine->wa_ctx.obj = NULL;
                return ret;
        }

        ret = i915_gem_obj_ggtt_pin(engine->wa_ctx.obj, PAGE_SIZE, 0);
        if (ret) {
                DRM_DEBUG_DRIVER("pin LRC WA ctx backing obj failed: %d\n",
                                 ret);
                drm_gem_object_unreference(&engine->wa_ctx.obj->base);
                return ret;
        }

        return 0;
}

static void lrc_destroy_wa_ctx_obj(struct intel_engine_cs *engine)
{
        if (engine->wa_ctx.obj) {
                i915_gem_object_ggtt_unpin(engine->wa_ctx.obj);
                drm_gem_object_unreference(&engine->wa_ctx.obj->base);
                engine->wa_ctx.obj = NULL;
        }
}

static int intel_init_workaround_bb(struct intel_engine_cs *engine)
{
        int ret;
        uint32_t *batch;
        uint32_t offset;
        struct page *page;
        struct i915_ctx_workarounds *wa_ctx = &engine->wa_ctx;

        WARN_ON(engine->id != RCS);

        /* update this when WA for higher Gen are added */
        if (INTEL_INFO(engine->dev)->gen > 9) {
                DRM_ERROR("WA batch buffer is not initialized for Gen%d\n",
                          INTEL_INFO(engine->dev)->gen);
                return 0;
        }

        /* some WA perform writes to scratch page, ensure it is valid */
        if (engine->scratch.obj == NULL) {
                DRM_ERROR("scratch page not allocated for %s\n", engine->name);
                return -EINVAL;
        }

        ret = lrc_setup_wa_ctx_obj(engine, PAGE_SIZE);
        if (ret) {
                DRM_DEBUG_DRIVER("Failed to setup context WA page: %d\n", ret);
                return ret;
        }

        page = i915_gem_object_get_dirty_page(wa_ctx->obj, 0);
        batch = kmap_atomic(page);
        offset = 0;

        if (INTEL_INFO(engine->dev)->gen == 8) {
                ret = gen8_init_indirectctx_bb(engine,
                                               &wa_ctx->indirect_ctx,
                                               batch,
                                               &offset);
                if (ret)
                        goto out;

                ret = gen8_init_perctx_bb(engine,
                                          &wa_ctx->per_ctx,
                                          batch,
                                          &offset);
                if (ret)
                        goto out;
        } else if (INTEL_INFO(engine->dev)->gen == 9) {
                ret = gen9_init_indirectctx_bb(engine,
                                               &wa_ctx->indirect_ctx,
                                               batch,
                                               &offset);
                if (ret)
                        goto out;

                ret = gen9_init_perctx_bb(engine,
                                          &wa_ctx->per_ctx,
                                          batch,
                                          &offset);
                if (ret)
                        goto out;
        }

out:
        kunmap_atomic(batch);
        if (ret)
                lrc_destroy_wa_ctx_obj(engine);

        return ret;
}

static void lrc_init_hws(struct intel_engine_cs *engine)
{
        struct drm_i915_private *dev_priv = engine->dev->dev_private;

        I915_WRITE(RING_HWS_PGA(engine->mmio_base),
                   (u32)engine->status_page.gfx_addr);
        POSTING_READ(RING_HWS_PGA(engine->mmio_base));
}

static int gen8_init_common_ring(struct intel_engine_cs *engine)
{
        struct drm_device *dev = engine->dev;
        struct drm_i915_private *dev_priv = dev->dev_private;
        unsigned int next_context_status_buffer_hw;

        lrc_init_hws(engine);

        I915_WRITE_IMR(engine,
                       ~(engine->irq_enable_mask | engine->irq_keep_mask));
        I915_WRITE(RING_HWSTAM(engine->mmio_base), 0xffffffff);

        I915_WRITE(RING_MODE_GEN7(engine),
                   _MASKED_BIT_DISABLE(GFX_REPLAY_MODE) |
                   _MASKED_BIT_ENABLE(GFX_RUN_LIST_ENABLE));
        POSTING_READ(RING_MODE_GEN7(engine));

        /*
         * Instead of resetting the Context Status Buffer (CSB) read pointer to
         * zero, we need to read the write pointer from hardware and use its
         * value because "this register is power context save restored".
         * Effectively, these states have been observed:
         *
         *      | Suspend-to-idle (freeze) | Suspend-to-RAM (mem) |
         * BDW  | CSB regs not reset       | CSB regs reset       |
         * CHT  | CSB regs not reset       | CSB regs not reset   |
         * SKL  |         ?                |         ?            |
         * BXT  |         ?                |         ?            |
         */
        next_context_status_buffer_hw =
                GEN8_CSB_WRITE_PTR(I915_READ(RING_CONTEXT_STATUS_PTR(engine)));

        /*
         * When the CSB registers are reset (also after power-up / gpu reset),
         * CSB write pointer is set to all 1's, which is not valid, use '5' in
         * this special case, so the first element read is CSB[0].
         */
        if (next_context_status_buffer_hw == GEN8_CSB_PTR_MASK)
                next_context_status_buffer_hw = (GEN8_CSB_ENTRIES - 1);

        engine->next_context_status_buffer = next_context_status_buffer_hw;
        DRM_DEBUG_DRIVER("Execlists enabled for %s\n", engine->name);

        intel_engine_init_hangcheck(engine);

        return intel_mocs_init_engine(engine);
}

static int gen8_init_render_ring(struct intel_engine_cs *engine)
{
        struct drm_device *dev = engine->dev;
        struct drm_i915_private *dev_priv = dev->dev_private;
        int ret;

        ret = gen8_init_common_ring(engine);
        if (ret)
                return ret;

        /* We need to disable the AsyncFlip performance optimisations in order
         * to use MI_WAIT_FOR_EVENT within the CS. It should already be
         * programmed to '1' on all products.
         *
         * WaDisableAsyncFlipPerfMode:snb,ivb,hsw,vlv,bdw,chv
         */
        I915_WRITE(MI_MODE, _MASKED_BIT_ENABLE(ASYNC_FLIP_PERF_DISABLE));

        I915_WRITE(INSTPM, _MASKED_BIT_ENABLE(INSTPM_FORCE_ORDERING));

        return init_workarounds_ring(engine);
}

static int gen9_init_render_ring(struct intel_engine_cs *engine)
{
        int ret;

        ret = gen8_init_common_ring(engine);
        if (ret)
                return ret;

        return init_workarounds_ring(engine);
}

static int intel_logical_ring_emit_pdps(struct drm_i915_gem_request *req)
{
        struct i915_hw_ppgtt *ppgtt = req->ctx->ppgtt;
        struct intel_engine_cs *engine = req->engine;
        struct intel_ringbuffer *ringbuf = req->ringbuf;
        const int num_lri_cmds = GEN8_LEGACY_PDPES * 2;
        int i, ret;

        ret = intel_ring_begin(req, num_lri_cmds * 2 + 2);
        if (ret)
                return ret;

        intel_logical_ring_emit(ringbuf, MI_LOAD_REGISTER_IMM(num_lri_cmds));
        for (i = GEN8_LEGACY_PDPES - 1; i >= 0; i--) {
                const dma_addr_t pd_daddr = i915_page_dir_dma_addr(ppgtt, i);

                intel_logical_ring_emit_reg(ringbuf,
                                            GEN8_RING_PDP_UDW(engine, i));
                intel_logical_ring_emit(ringbuf, upper_32_bits(pd_daddr));
                intel_logical_ring_emit_reg(ringbuf,
                                            GEN8_RING_PDP_LDW(engine, i));
                intel_logical_ring_emit(ringbuf, lower_32_bits(pd_daddr));
        }

        intel_logical_ring_emit(ringbuf, MI_NOOP);
        intel_logical_ring_advance(ringbuf);

        return 0;
}

static int gen8_emit_bb_start(struct drm_i915_gem_request *req,
                              u64 offset, unsigned dispatch_flags)
{
        struct intel_ringbuffer *ringbuf = req->ringbuf;
        bool ppgtt = !(dispatch_flags & I915_DISPATCH_SECURE);
        int ret;

        /* Don't rely in hw updating PDPs, specially in lite-restore.
         * Ideally, we should set Force PD Restore in ctx descriptor,
         * but we can't. Force Restore would be a second option, but
         * it is unsafe in case of lite-restore (because the ctx is
         * not idle). PML4 is allocated during ppgtt init so this is
         * not needed in 48-bit.*/
        if (req->ctx->ppgtt &&
            (intel_engine_flag(req->engine) & req->ctx->ppgtt->pd_dirty_rings)) {
                if (!USES_FULL_48BIT_PPGTT(req->i915) &&
                    !intel_vgpu_active(req->i915->dev)) {
                        ret = intel_logical_ring_emit_pdps(req);
                        if (ret)
                                return ret;
                }

                req->ctx->ppgtt->pd_dirty_rings &= ~intel_engine_flag(req->engine);
        }

        ret = intel_ring_begin(req, 4);
        if (ret)
                return ret;

        /* FIXME(BDW): Address space and security selectors. */
        intel_logical_ring_emit(ringbuf, MI_BATCH_BUFFER_START_GEN8 |
                                (ppgtt<<8) |
                                (dispatch_flags & I915_DISPATCH_RS ?
                                 MI_BATCH_RESOURCE_STREAMER : 0));
        intel_logical_ring_emit(ringbuf, lower_32_bits(offset));
        intel_logical_ring_emit(ringbuf, upper_32_bits(offset));
        intel_logical_ring_emit(ringbuf, MI_NOOP);
        intel_logical_ring_advance(ringbuf);

        return 0;
}

static bool gen8_logical_ring_get_irq(struct intel_engine_cs *engine)
{
        struct drm_device *dev = engine->dev;
        struct drm_i915_private *dev_priv = dev->dev_private;
        unsigned long flags;

        if (WARN_ON(!intel_irqs_enabled(dev_priv)))
                return false;

        spin_lock_irqsave(&dev_priv->irq_lock, flags);
        if (engine->irq_refcount++ == 0) {
                I915_WRITE_IMR(engine,
                               ~(engine->irq_enable_mask | engine->irq_keep_mask));
                POSTING_READ(RING_IMR(engine->mmio_base));
        }
        spin_unlock_irqrestore(&dev_priv->irq_lock, flags);

        return true;
}

static void gen8_logical_ring_put_irq(struct intel_engine_cs *engine)
{
        struct drm_device *dev = engine->dev;
        struct drm_i915_private *dev_priv = dev->dev_private;
        unsigned long flags;

        spin_lock_irqsave(&dev_priv->irq_lock, flags);
        if (--engine->irq_refcount == 0) {
                I915_WRITE_IMR(engine, ~engine->irq_keep_mask);
                POSTING_READ(RING_IMR(engine->mmio_base));
        }
        spin_unlock_irqrestore(&dev_priv->irq_lock, flags);
}

static int gen8_emit_flush(struct drm_i915_gem_request *request,
                           u32 invalidate_domains,
                           u32 unused)
{
        struct intel_ringbuffer *ringbuf = request->ringbuf;
        struct intel_engine_cs *engine = ringbuf->engine;
        struct drm_device *dev = engine->dev;
        struct drm_i915_private *dev_priv = dev->dev_private;
        uint32_t cmd;
        int ret;

        ret = intel_ring_begin(request, 4);
        if (ret)
                return ret;

        cmd = MI_FLUSH_DW + 1;

        /* We always require a command barrier so that subsequent
         * commands, such as breadcrumb interrupts, are strictly ordered
         * wrt the contents of the write cache being flushed to memory
         * (and thus being coherent from the CPU).
         */
        cmd |= MI_FLUSH_DW_STORE_INDEX | MI_FLUSH_DW_OP_STOREDW;

        if (invalidate_domains & I915_GEM_GPU_DOMAINS) {
                cmd |= MI_INVALIDATE_TLB;
                if (engine == &dev_priv->engine[VCS])
                        cmd |= MI_INVALIDATE_BSD;
        }

        intel_logical_ring_emit(ringbuf, cmd);
        intel_logical_ring_emit(ringbuf,
                                I915_GEM_HWS_SCRATCH_ADDR |
                                MI_FLUSH_DW_USE_GTT);
        intel_logical_ring_emit(ringbuf, 0); /* upper addr */
        intel_logical_ring_emit(ringbuf, 0); /* value */
        intel_logical_ring_advance(ringbuf);

        return 0;
}

static int gen8_emit_flush_render(struct drm_i915_gem_request *request,
                                  u32 invalidate_domains,
                                  u32 flush_domains)
{
        struct intel_ringbuffer *ringbuf = request->ringbuf;
        struct intel_engine_cs *engine = ringbuf->engine;
        u32 scratch_addr = engine->scratch.gtt_offset + 2 * CACHELINE_BYTES;
        bool vf_flush_wa = false;
        u32 flags = 0;
        int ret;

        flags |= PIPE_CONTROL_CS_STALL;

        if (flush_domains) {
                flags |= PIPE_CONTROL_RENDER_TARGET_CACHE_FLUSH;
                flags |= PIPE_CONTROL_DEPTH_CACHE_FLUSH;
                flags |= PIPE_CONTROL_DC_FLUSH_ENABLE;
                flags |= PIPE_CONTROL_FLUSH_ENABLE;
        }

        if (invalidate_domains) {
                flags |= PIPE_CONTROL_TLB_INVALIDATE;
                flags |= PIPE_CONTROL_INSTRUCTION_CACHE_INVALIDATE;
                flags |= PIPE_CONTROL_TEXTURE_CACHE_INVALIDATE;
                flags |= PIPE_CONTROL_VF_CACHE_INVALIDATE;
                flags |= PIPE_CONTROL_CONST_CACHE_INVALIDATE;
                flags |= PIPE_CONTROL_STATE_CACHE_INVALIDATE;
                flags |= PIPE_CONTROL_QW_WRITE;
                flags |= PIPE_CONTROL_GLOBAL_GTT_IVB;

                /*
                 * On GEN9: before VF_CACHE_INVALIDATE we need to emit a NULL
                 * pipe control.
                 */
                if (IS_GEN9(engine->dev))
                        vf_flush_wa = true;
        }

        ret = intel_ring_begin(request, vf_flush_wa ? 12 : 6);
        if (ret)
                return ret;

        if (vf_flush_wa) {
                intel_logical_ring_emit(ringbuf, GFX_OP_PIPE_CONTROL(6));
                intel_logical_ring_emit(ringbuf, 0);
                intel_logical_ring_emit(ringbuf, 0);
                intel_logical_ring_emit(ringbuf, 0);
                intel_logical_ring_emit(ringbuf, 0);
                intel_logical_ring_emit(ringbuf, 0);
        }

        intel_logical_ring_emit(ringbuf, GFX_OP_PIPE_CONTROL(6));
        intel_logical_ring_emit(ringbuf, flags);
        intel_logical_ring_emit(ringbuf, scratch_addr);
        intel_logical_ring_emit(ringbuf, 0);
        intel_logical_ring_emit(ringbuf, 0);
        intel_logical_ring_emit(ringbuf, 0);
        intel_logical_ring_advance(ringbuf);

        return 0;
}

static u32 gen8_get_seqno(struct intel_engine_cs *engine)
{
        return intel_read_status_page(engine, I915_GEM_HWS_INDEX);
}

static void gen8_set_seqno(struct intel_engine_cs *engine, u32 seqno)
{
        intel_write_status_page(engine, I915_GEM_HWS_INDEX, seqno);
}

static void bxt_a_seqno_barrier(struct intel_engine_cs *engine)
{
        /*
         * On BXT A steppings there is a HW coherency issue whereby the
         * MI_STORE_DATA_IMM storing the completed request's seqno
         * occasionally doesn't invalidate the CPU cache. Work around this by
         * clflushing the corresponding cacheline whenever the caller wants
         * the coherency to be guaranteed. Note that this cacheline is known
         * to be clean at this point, since we only write it in
         * bxt_a_set_seqno(), where we also do a clflush after the write. So
         * this clflush in practice becomes an invalidate operation.
         */
        intel_flush_status_page(engine, I915_GEM_HWS_INDEX);
}

static void bxt_a_set_seqno(struct intel_engine_cs *engine, u32 seqno)
{
        intel_write_status_page(engine, I915_GEM_HWS_INDEX, seqno);

        /* See bxt_a_get_seqno() explaining the reason for the clflush. */
        intel_flush_status_page(engine, I915_GEM_HWS_INDEX);
}

/*
 * Reserve space for 2 NOOPs at the end of each request to be
 * used as a workaround for not being allowed to do lite
 * restore with HEAD==TAIL (WaIdleLiteRestore).
 */
#define WA_TAIL_DWORDS 2

static inline u32 hws_seqno_address(struct intel_engine_cs *engine)
{
        return engine->status_page.gfx_addr + I915_GEM_HWS_INDEX_ADDR;
}

static int gen8_emit_request(struct drm_i915_gem_request *request)
{
        struct intel_ringbuffer *ringbuf = request->ringbuf;
        int ret;

        ret = intel_ring_begin(request, 6 + WA_TAIL_DWORDS);
        if (ret)
                return ret;

        /* w/a: bit 5 needs to be zero for MI_FLUSH_DW address. */
        BUILD_BUG_ON(I915_GEM_HWS_INDEX_ADDR & (1 << 5));

        intel_logical_ring_emit(ringbuf,
                                (MI_FLUSH_DW + 1) | MI_FLUSH_DW_OP_STOREDW);
        intel_logical_ring_emit(ringbuf,
                                hws_seqno_address(request->engine) |
                                MI_FLUSH_DW_USE_GTT);
        intel_logical_ring_emit(ringbuf, 0);
        intel_logical_ring_emit(ringbuf, i915_gem_request_get_seqno(request));
        intel_logical_ring_emit(ringbuf, MI_USER_INTERRUPT);
        intel_logical_ring_emit(ringbuf, MI_NOOP);
        return intel_logical_ring_advance_and_submit(request);
}

static int gen8_emit_request_render(struct drm_i915_gem_request *request)
{
        struct intel_ringbuffer *ringbuf = request->ringbuf;
        int ret;

        ret = intel_ring_begin(request, 8 + WA_TAIL_DWORDS);
        if (ret)
                return ret;

        /* We're using qword write, seqno should be aligned to 8 bytes. */
        BUILD_BUG_ON(I915_GEM_HWS_INDEX & 1);

        /* w/a for post sync ops following a GPGPU operation we
         * need a prior CS_STALL, which is emitted by the flush
         * following the batch.
         */
        intel_logical_ring_emit(ringbuf, GFX_OP_PIPE_CONTROL(6));
        intel_logical_ring_emit(ringbuf,
                                (PIPE_CONTROL_GLOBAL_GTT_IVB |
                                 PIPE_CONTROL_CS_STALL |
                                 PIPE_CONTROL_QW_WRITE));
        intel_logical_ring_emit(ringbuf, hws_seqno_address(request->engine));
        intel_logical_ring_emit(ringbuf, 0);
        intel_logical_ring_emit(ringbuf, i915_gem_request_get_seqno(request));
        /* We're thrashing one dword of HWS. */
        intel_logical_ring_emit(ringbuf, 0);
        intel_logical_ring_emit(ringbuf, MI_USER_INTERRUPT);
        intel_logical_ring_emit(ringbuf, MI_NOOP);
        return intel_logical_ring_advance_and_submit(request);
}

static int intel_lr_context_render_state_init(struct drm_i915_gem_request *req)
{
        struct render_state so;
        int ret;

        ret = i915_gem_render_state_prepare(req->engine, &so);
        if (ret)
                return ret;

        if (so.rodata == NULL)
                return 0;

        ret = req->engine->emit_bb_start(req, so.ggtt_offset,
                                       I915_DISPATCH_SECURE);
        if (ret)
                goto out;

        ret = req->engine->emit_bb_start(req,
                                       (so.ggtt_offset + so.aux_batch_offset),
                                       I915_DISPATCH_SECURE);
        if (ret)
                goto out;

        i915_vma_move_to_active(i915_gem_obj_to_ggtt(so.obj), req);

out:
        i915_gem_render_state_fini(&so);
        return ret;
}

static int gen8_init_rcs_context(struct drm_i915_gem_request *req)
{
        int ret;

        ret = intel_logical_ring_workarounds_emit(req);
        if (ret)
                return ret;

        ret = intel_rcs_context_init_mocs(req);
        /*
         * Failing to program the MOCS is non-fatal.The system will not
         * run at peak performance. So generate an error and carry on.
         */
        if (ret)
                DRM_ERROR("MOCS failed to program: expect performance issues.\n");

        return intel_lr_context_render_state_init(req);
}

/**
 * intel_logical_ring_cleanup() - deallocate the Engine Command Streamer
 *
 * @ring: Engine Command Streamer.
 *
 */
void intel_logical_ring_cleanup(struct intel_engine_cs *engine)
{
        struct drm_i915_private *dev_priv;

        if (!intel_engine_initialized(engine))
                return;

        /*
         * Tasklet cannot be active at this point due intel_mark_active/idle
         * so this is just for documentation.
         */
        if (WARN_ON(test_bit(TASKLET_STATE_SCHED, &engine->irq_tasklet.state)))
                tasklet_kill(&engine->irq_tasklet);

        dev_priv = engine->dev->dev_private;

        if (engine->buffer) {
                intel_logical_ring_stop(engine);
                WARN_ON((I915_READ_MODE(engine) & MODE_IDLE) == 0);
        }

        if (engine->cleanup)
                engine->cleanup(engine);

        i915_cmd_parser_fini_ring(engine);
        i915_gem_batch_pool_fini(&engine->batch_pool);

        if (engine->status_page.obj) {
                i915_gem_object_unpin_map(engine->status_page.obj);
                engine->status_page.obj = NULL;
        }

        engine->idle_lite_restore_wa = 0;
        engine->disable_lite_restore_wa = false;
        engine->ctx_desc_template = 0;

        lrc_destroy_wa_ctx_obj(engine);
        engine->dev = NULL;
}

static void
logical_ring_default_vfuncs(struct drm_device *dev,
                            struct intel_engine_cs *engine)
{
        /* Default vfuncs which can be overriden by each engine. */
        engine->init_hw = gen8_init_common_ring;
        engine->emit_request = gen8_emit_request;
        engine->emit_flush = gen8_emit_flush;
        engine->irq_get = gen8_logical_ring_get_irq;
        engine->irq_put = gen8_logical_ring_put_irq;
        engine->emit_bb_start = gen8_emit_bb_start;
        engine->get_seqno = gen8_get_seqno;
        engine->set_seqno = gen8_set_seqno;
        if (IS_BXT_REVID(dev, 0, BXT_REVID_A1)) {
                engine->irq_seqno_barrier = bxt_a_seqno_barrier;
                engine->set_seqno = bxt_a_set_seqno;
        }
}

static inline void
logical_ring_default_irqs(struct intel_engine_cs *engine, unsigned shift)
{
        engine->irq_enable_mask = GT_RENDER_USER_INTERRUPT << shift;
        engine->irq_keep_mask = GT_CONTEXT_SWITCH_INTERRUPT << shift;
}

static int
lrc_setup_hws(struct intel_engine_cs *engine,
              struct drm_i915_gem_object *dctx_obj)
{
        void *hws;

        /* The HWSP is part of the default context object in LRC mode. */
        engine->status_page.gfx_addr = i915_gem_obj_ggtt_offset(dctx_obj) +
                                       LRC_PPHWSP_PN * PAGE_SIZE;
        hws = i915_gem_object_pin_map(dctx_obj);
        if (IS_ERR(hws))
                return PTR_ERR(hws);
        engine->status_page.page_addr = hws + LRC_PPHWSP_PN * PAGE_SIZE;
        engine->status_page.obj = dctx_obj;

        return 0;
}

static int
logical_ring_init(struct drm_device *dev, struct intel_engine_cs *engine)
{
        struct drm_i915_private *dev_priv = to_i915(dev);
        struct intel_context *dctx = dev_priv->kernel_context;
        enum forcewake_domains fw_domains;
        int ret;

        /* Intentionally left blank. */
        engine->buffer = NULL;

        engine->dev = dev;
        INIT_LIST_HEAD(&engine->active_list);
        INIT_LIST_HEAD(&engine->request_list);
        i915_gem_batch_pool_init(dev, &engine->batch_pool);
        init_waitqueue_head(&engine->irq_queue);

        INIT_LIST_HEAD(&engine->buffers);
        INIT_LIST_HEAD(&engine->execlist_queue);
        INIT_LIST_HEAD(&engine->execlist_retired_req_list);
        spin_lock_init(&engine->execlist_lock);

        tasklet_init(&engine->irq_tasklet,
                     intel_lrc_irq_handler, (unsigned long)engine);

        logical_ring_init_platform_invariants(engine);

        fw_domains = intel_uncore_forcewake_for_reg(dev_priv,
                                                    RING_ELSP(engine),
                                                    FW_REG_WRITE);

        fw_domains |= intel_uncore_forcewake_for_reg(dev_priv,
                                                     RING_CONTEXT_STATUS_PTR(engine),
                                                     FW_REG_READ | FW_REG_WRITE);

        fw_domains |= intel_uncore_forcewake_for_reg(dev_priv,
                                                     RING_CONTEXT_STATUS_BUF_BASE(engine),
                                                     FW_REG_READ);

        engine->fw_domains = fw_domains;

        ret = i915_cmd_parser_init_ring(engine);
        if (ret)
                goto error;

        ret = intel_lr_context_deferred_alloc(dctx, engine);
        if (ret)
                goto error;

        /* As this is the default context, always pin it */
        ret = intel_lr_context_do_pin(dctx, engine);
        if (ret) {
                DRM_ERROR(
                        "Failed to pin and map ringbuffer %s: %d\n",
                        engine->name, ret);
                goto error;
        }

        /* And setup the hardware status page. */
        ret = lrc_setup_hws(engine, dctx->engine[engine->id].state);
        if (ret) {
                DRM_ERROR("Failed to set up hws %s: %d\n", engine->name, ret);
                goto error;
        }

        return 0;

error:
        intel_logical_ring_cleanup(engine);
        return ret;
}

static int logical_render_ring_init(struct drm_device *dev)
{
        struct drm_i915_private *dev_priv = dev->dev_private;
        struct intel_engine_cs *engine = &dev_priv->engine[RCS];
        int ret;

        engine->name = "render ring";
        engine->id = RCS;
        engine->exec_id = I915_EXEC_RENDER;
        engine->guc_id = GUC_RENDER_ENGINE;
        engine->mmio_base = RENDER_RING_BASE;

        logical_ring_default_irqs(engine, GEN8_RCS_IRQ_SHIFT);
        if (HAS_L3_DPF(dev))
                engine->irq_keep_mask |= GT_RENDER_L3_PARITY_ERROR_INTERRUPT;

        logical_ring_default_vfuncs(dev, engine);

        /* Override some for render ring. */
        if (INTEL_INFO(dev)->gen >= 9)
                engine->init_hw = gen9_init_render_ring;
        else
                engine->init_hw = gen8_init_render_ring;
        engine->init_context = gen8_init_rcs_context;
        engine->cleanup = intel_fini_pipe_control;
        engine->emit_flush = gen8_emit_flush_render;
        engine->emit_request = gen8_emit_request_render;

        engine->dev = dev;

        ret = intel_init_pipe_control(engine);
        if (ret)
                return ret;

        ret = intel_init_workaround_bb(engine);
        if (ret) {
                /*
                 * We continue even if we fail to initialize WA batch
                 * because we only expect rare glitches but nothing
                 * critical to prevent us from using GPU
                 */
                DRM_ERROR("WA batch buffer initialization failed: %d\n",
                          ret);
        }

        ret = logical_ring_init(dev, engine);
        if (ret) {
                lrc_destroy_wa_ctx_obj(engine);
        }

        return ret;
}

static int logical_bsd_ring_init(struct drm_device *dev)
{
        struct drm_i915_private *dev_priv = dev->dev_private;
        struct intel_engine_cs *engine = &dev_priv->engine[VCS];

        engine->name = "bsd ring";
        engine->id = VCS;
        engine->exec_id = I915_EXEC_BSD;
        engine->guc_id = GUC_VIDEO_ENGINE;
        engine->mmio_base = GEN6_BSD_RING_BASE;

        logical_ring_default_irqs(engine, GEN8_VCS1_IRQ_SHIFT);
        logical_ring_default_vfuncs(dev, engine);

        return logical_ring_init(dev, engine);
}

static int logical_bsd2_ring_init(struct drm_device *dev)
{
        struct drm_i915_private *dev_priv = dev->dev_private;
        struct intel_engine_cs *engine = &dev_priv->engine[VCS2];

        engine->name = "bsd2 ring";
        engine->id = VCS2;
        engine->exec_id = I915_EXEC_BSD;
        engine->guc_id = GUC_VIDEO_ENGINE2;
        engine->mmio_base = GEN8_BSD2_RING_BASE;

        logical_ring_default_irqs(engine, GEN8_VCS2_IRQ_SHIFT);
        logical_ring_default_vfuncs(dev, engine);

        return logical_ring_init(dev, engine);
}

static int logical_blt_ring_init(struct drm_device *dev)
{
        struct drm_i915_private *dev_priv = dev->dev_private;
        struct intel_engine_cs *engine = &dev_priv->engine[BCS];

        engine->name = "blitter ring";
        engine->id = BCS;
        engine->exec_id = I915_EXEC_BLT;
        engine->guc_id = GUC_BLITTER_ENGINE;
        engine->mmio_base = BLT_RING_BASE;

        logical_ring_default_irqs(engine, GEN8_BCS_IRQ_SHIFT);
        logical_ring_default_vfuncs(dev, engine);

        return logical_ring_init(dev, engine);
}

static int logical_vebox_ring_init(struct drm_device *dev)
{
        struct drm_i915_private *dev_priv = dev->dev_private;
        struct intel_engine_cs *engine = &dev_priv->engine[VECS];

        engine->name = "video enhancement ring";
        engine->id = VECS;
        engine->exec_id = I915_EXEC_VEBOX;
        engine->guc_id = GUC_VIDEOENHANCE_ENGINE;
        engine->mmio_base = VEBOX_RING_BASE;

        logical_ring_default_irqs(engine, GEN8_VECS_IRQ_SHIFT);
        logical_ring_default_vfuncs(dev, engine);

        return logical_ring_init(dev, engine);
}

/**
 * intel_logical_rings_init() - allocate, populate and init the Engine Command Streamers
 * @dev: DRM device.
 *
 * This function inits the engines for an Execlists submission style (the equivalent in the
 * legacy ringbuffer submission world would be i915_gem_init_engines). It does it only for
 * those engines that are present in the hardware.
 *
 * Return: non-zero if the initialization failed.
 */
int intel_logical_rings_init(struct drm_device *dev)
{
        struct drm_i915_private *dev_priv = dev->dev_private;
        int ret;

        ret = logical_render_ring_init(dev);
        if (ret)
                return ret;

        if (HAS_BSD(dev)) {
                ret = logical_bsd_ring_init(dev);
                if (ret)
                        goto cleanup_render_ring;
        }

        if (HAS_BLT(dev)) {
                ret = logical_blt_ring_init(dev);
                if (ret)
                        goto cleanup_bsd_ring;
        }

        if (HAS_VEBOX(dev)) {
                ret = logical_vebox_ring_init(dev);
                if (ret)
                        goto cleanup_blt_ring;
        }

        if (HAS_BSD2(dev)) {
                ret = logical_bsd2_ring_init(dev);
                if (ret)
                        goto cleanup_vebox_ring;
        }

        return 0;

cleanup_vebox_ring:
        intel_logical_ring_cleanup(&dev_priv->engine[VECS]);
cleanup_blt_ring:
        intel_logical_ring_cleanup(&dev_priv->engine[BCS]);
cleanup_bsd_ring:
        intel_logical_ring_cleanup(&dev_priv->engine[VCS]);
cleanup_render_ring:
        intel_logical_ring_cleanup(&dev_priv->engine[RCS]);

        return ret;
}

static u32
make_rpcs(struct drm_device *dev)
{
        u32 rpcs = 0;

        /*
         * No explicit RPCS request is needed to ensure full
         * slice/subslice/EU enablement prior to Gen9.
        */
        if (INTEL_INFO(dev)->gen < 9)
                return 0;

        /*
         * Starting in Gen9, render power gating can leave
         * slice/subslice/EU in a partially enabled state. We
         * must make an explicit request through RPCS for full
         * enablement.
        */
        if (INTEL_INFO(dev)->has_slice_pg) {
                rpcs |= GEN8_RPCS_S_CNT_ENABLE;
                rpcs |= INTEL_INFO(dev)->slice_total <<
                        GEN8_RPCS_S_CNT_SHIFT;
                rpcs |= GEN8_RPCS_ENABLE;
        }

        if (INTEL_INFO(dev)->has_subslice_pg) {
                rpcs |= GEN8_RPCS_SS_CNT_ENABLE;
                rpcs |= INTEL_INFO(dev)->subslice_per_slice <<
                        GEN8_RPCS_SS_CNT_SHIFT;
                rpcs |= GEN8_RPCS_ENABLE;
        }

        if (INTEL_INFO(dev)->has_eu_pg) {
                rpcs |= INTEL_INFO(dev)->eu_per_subslice <<
                        GEN8_RPCS_EU_MIN_SHIFT;
                rpcs |= INTEL_INFO(dev)->eu_per_subslice <<
                        GEN8_RPCS_EU_MAX_SHIFT;
                rpcs |= GEN8_RPCS_ENABLE;
        }

        return rpcs;
}

static u32 intel_lr_indirect_ctx_offset(struct intel_engine_cs *engine)
{
        u32 indirect_ctx_offset;

        switch (INTEL_INFO(engine->dev)->gen) {
        default:
                MISSING_CASE(INTEL_INFO(engine->dev)->gen);
                /* fall through */
        case 9:
                indirect_ctx_offset =
                        GEN9_CTX_RCS_INDIRECT_CTX_OFFSET_DEFAULT;
                break;
        case 8:
                indirect_ctx_offset =
                        GEN8_CTX_RCS_INDIRECT_CTX_OFFSET_DEFAULT;
                break;
        }

        return indirect_ctx_offset;
}

static int
populate_lr_context(struct intel_context *ctx,
                    struct drm_i915_gem_object *ctx_obj,
                    struct intel_engine_cs *engine,
                    struct intel_ringbuffer *ringbuf)
{
        struct drm_device *dev = engine->dev;
        struct drm_i915_private *dev_priv = dev->dev_private;
        struct i915_hw_ppgtt *ppgtt = ctx->ppgtt;
        void *vaddr;
        u32 *reg_state;
        int ret;

        if (!ppgtt)
                ppgtt = dev_priv->mm.aliasing_ppgtt;

        ret = i915_gem_object_set_to_cpu_domain(ctx_obj, true);
        if (ret) {
                DRM_DEBUG_DRIVER("Could not set to CPU domain\n");
                return ret;
        }

        vaddr = i915_gem_object_pin_map(ctx_obj);
        if (IS_ERR(vaddr)) {
                ret = PTR_ERR(vaddr);
                DRM_DEBUG_DRIVER("Could not map object pages! (%d)\n", ret);
                return ret;
        }
        ctx_obj->dirty = true;

        /* The second page of the context object contains some fields which must
         * be set up prior to the first execution. */
        reg_state = vaddr + LRC_STATE_PN * PAGE_SIZE;

        /* A context is actually a big batch buffer with several MI_LOAD_REGISTER_IMM
         * commands followed by (reg, value) pairs. The values we are setting here are
         * only for the first context restore: on a subsequent save, the GPU will
         * recreate this batchbuffer with new values (including all the missing
         * MI_LOAD_REGISTER_IMM commands that we are not initializing here). */
        reg_state[CTX_LRI_HEADER_0] =
                MI_LOAD_REGISTER_IMM(engine->id == RCS ? 14 : 11) | MI_LRI_FORCE_POSTED;
        ASSIGN_CTX_REG(reg_state, CTX_CONTEXT_CONTROL,
                       RING_CONTEXT_CONTROL(engine),
                       _MASKED_BIT_ENABLE(CTX_CTRL_INHIBIT_SYN_CTX_SWITCH |
                                          CTX_CTRL_ENGINE_CTX_RESTORE_INHIBIT |
                                          (HAS_RESOURCE_STREAMER(dev) ?
                                            CTX_CTRL_RS_CTX_ENABLE : 0)));
        ASSIGN_CTX_REG(reg_state, CTX_RING_HEAD, RING_HEAD(engine->mmio_base),
                       0);
        ASSIGN_CTX_REG(reg_state, CTX_RING_TAIL, RING_TAIL(engine->mmio_base),
                       0);
        /* Ring buffer start address is not known until the buffer is pinned.
         * It is written to the context image in execlists_update_context()
         */
        ASSIGN_CTX_REG(reg_state, CTX_RING_BUFFER_START,
                       RING_START(engine->mmio_base), 0);
        ASSIGN_CTX_REG(reg_state, CTX_RING_BUFFER_CONTROL,
                       RING_CTL(engine->mmio_base),
                       ((ringbuf->size - PAGE_SIZE) & RING_NR_PAGES) | RING_VALID);
        ASSIGN_CTX_REG(reg_state, CTX_BB_HEAD_U,
                       RING_BBADDR_UDW(engine->mmio_base), 0);
        ASSIGN_CTX_REG(reg_state, CTX_BB_HEAD_L,
                       RING_BBADDR(engine->mmio_base), 0);
        ASSIGN_CTX_REG(reg_state, CTX_BB_STATE,
                       RING_BBSTATE(engine->mmio_base),
                       RING_BB_PPGTT);
        ASSIGN_CTX_REG(reg_state, CTX_SECOND_BB_HEAD_U,
                       RING_SBBADDR_UDW(engine->mmio_base), 0);
        ASSIGN_CTX_REG(reg_state, CTX_SECOND_BB_HEAD_L,
                       RING_SBBADDR(engine->mmio_base), 0);
        ASSIGN_CTX_REG(reg_state, CTX_SECOND_BB_STATE,
                       RING_SBBSTATE(engine->mmio_base), 0);
        if (engine->id == RCS) {
                ASSIGN_CTX_REG(reg_state, CTX_BB_PER_CTX_PTR,
                               RING_BB_PER_CTX_PTR(engine->mmio_base), 0);
                ASSIGN_CTX_REG(reg_state, CTX_RCS_INDIRECT_CTX,
                               RING_INDIRECT_CTX(engine->mmio_base), 0);
                ASSIGN_CTX_REG(reg_state, CTX_RCS_INDIRECT_CTX_OFFSET,
                               RING_INDIRECT_CTX_OFFSET(engine->mmio_base), 0);
                if (engine->wa_ctx.obj) {
                        struct i915_ctx_workarounds *wa_ctx = &engine->wa_ctx;
                        uint32_t ggtt_offset = i915_gem_obj_ggtt_offset(wa_ctx->obj);

                        reg_state[CTX_RCS_INDIRECT_CTX+1] =
                                (ggtt_offset + wa_ctx->indirect_ctx.offset * sizeof(uint32_t)) |
                                (wa_ctx->indirect_ctx.size / CACHELINE_DWORDS);

                        reg_state[CTX_RCS_INDIRECT_CTX_OFFSET+1] =
                                intel_lr_indirect_ctx_offset(engine) << 6;

                        reg_state[CTX_BB_PER_CTX_PTR+1] =
                                (ggtt_offset + wa_ctx->per_ctx.offset * sizeof(uint32_t)) |
                                0x01;
                }
        }
        reg_state[CTX_LRI_HEADER_1] = MI_LOAD_REGISTER_IMM(9) | MI_LRI_FORCE_POSTED;
        ASSIGN_CTX_REG(reg_state, CTX_CTX_TIMESTAMP,
                       RING_CTX_TIMESTAMP(engine->mmio_base), 0);
        /* PDP values well be assigned later if needed */
        ASSIGN_CTX_REG(reg_state, CTX_PDP3_UDW, GEN8_RING_PDP_UDW(engine, 3),
                       0);
        ASSIGN_CTX_REG(reg_state, CTX_PDP3_LDW, GEN8_RING_PDP_LDW(engine, 3),
                       0);
        ASSIGN_CTX_REG(reg_state, CTX_PDP2_UDW, GEN8_RING_PDP_UDW(engine, 2),
                       0);
        ASSIGN_CTX_REG(reg_state, CTX_PDP2_LDW, GEN8_RING_PDP_LDW(engine, 2),
                       0);
        ASSIGN_CTX_REG(reg_state, CTX_PDP1_UDW, GEN8_RING_PDP_UDW(engine, 1),
                       0);
        ASSIGN_CTX_REG(reg_state, CTX_PDP1_LDW, GEN8_RING_PDP_LDW(engine, 1),
                       0);
        ASSIGN_CTX_REG(reg_state, CTX_PDP0_UDW, GEN8_RING_PDP_UDW(engine, 0),
                       0);
        ASSIGN_CTX_REG(reg_state, CTX_PDP0_LDW, GEN8_RING_PDP_LDW(engine, 0),
                       0);

        if (USES_FULL_48BIT_PPGTT(ppgtt->base.dev)) {
                /* 64b PPGTT (48bit canonical)
                 * PDP0_DESCRIPTOR contains the base address to PML4 and
                 * other PDP Descriptors are ignored.
                 */
                ASSIGN_CTX_PML4(ppgtt, reg_state);
        } else {
                /* 32b PPGTT
                 * PDP*_DESCRIPTOR contains the base address of space supported.
                 * With dynamic page allocation, PDPs may not be allocated at
                 * this point. Point the unallocated PDPs to the scratch page
                 */
                execlists_update_context_pdps(ppgtt, reg_state);
        }

        if (engine->id == RCS) {
                reg_state[CTX_LRI_HEADER_2] = MI_LOAD_REGISTER_IMM(1);
                ASSIGN_CTX_REG(reg_state, CTX_R_PWR_CLK_STATE, GEN8_R_PWR_CLK_STATE,
                               make_rpcs(dev));
        }

        i915_gem_object_unpin_map(ctx_obj);

        return 0;
}

/**
 * intel_lr_context_free() - free the LRC specific bits of a context
 * @ctx: the LR context to free.
 *
 * The real context freeing is done in i915_gem_context_free: this only
 * takes care of the bits that are LRC related: the per-engine backing
 * objects and the logical ringbuffer.
 */
void intel_lr_context_free(struct intel_context *ctx)
{
        int i;

        for (i = I915_NUM_ENGINES; --i >= 0; ) {
                struct intel_ringbuffer *ringbuf = ctx->engine[i].ringbuf;
                struct drm_i915_gem_object *ctx_obj = ctx->engine[i].state;

                if (!ctx_obj)
                        continue;

                if (ctx == ctx->i915->kernel_context) {
                        intel_unpin_ringbuffer_obj(ringbuf);
                        i915_gem_object_ggtt_unpin(ctx_obj);
                        i915_gem_object_unpin_map(ctx_obj);
                }

                WARN_ON(ctx->engine[i].pin_count);
                intel_ringbuffer_free(ringbuf);
                drm_gem_object_unreference(&ctx_obj->base);
        }
}

/**
 * intel_lr_context_size() - return the size of the context for an engine
 * @ring: which engine to find the context size for
 *
 * Each engine may require a different amount of space for a context image,
 * so when allocating (or copying) an image, this function can be used to
 * find the right size for the specific engine.
 *
 * Return: size (in bytes) of an engine-specific context image
 *
 * Note: this size includes the HWSP, which is part of the context image
 * in LRC mode, but does not include the "shared data page" used with
 * GuC submission. The caller should account for this if using the GuC.
 */
uint32_t intel_lr_context_size(struct intel_engine_cs *engine)
{
        int ret = 0;

        WARN_ON(INTEL_INFO(engine->dev)->gen < 8);

        switch (engine->id) {
        case RCS:
                if (INTEL_INFO(engine->dev)->gen >= 9)
                        ret = GEN9_LR_CONTEXT_RENDER_SIZE;
                else
                        ret = GEN8_LR_CONTEXT_RENDER_SIZE;
                break;
        case VCS:
        case BCS:
        case VECS:
        case VCS2:
                ret = GEN8_LR_CONTEXT_OTHER_SIZE;
                break;
        }

        return ret;
}

/**
 * intel_lr_context_deferred_alloc() - create the LRC specific bits of a context
 * @ctx: LR context to create.
 * @ring: engine to be used with the context.
 *
 * This function can be called more than once, with different engines, if we plan
 * to use the context with them. The context backing objects and the ringbuffers
 * (specially the ringbuffer backing objects) suck a lot of memory up, and that's why
 * the creation is a deferred call: it's better to make sure first that we need to use
 * a given ring with the context.
 *
 * Return: non-zero on error.
 */

int intel_lr_context_deferred_alloc(struct intel_context *ctx,
                                    struct intel_engine_cs *engine)
{
        struct drm_device *dev = engine->dev;
        struct drm_i915_gem_object *ctx_obj;
        uint32_t context_size;
        struct intel_ringbuffer *ringbuf;
        int ret;

        WARN_ON(ctx->legacy_hw_ctx.rcs_state != NULL);
        WARN_ON(ctx->engine[engine->id].state);

        context_size = round_up(intel_lr_context_size(engine), 4096);

        /* One extra page as the sharing data between driver and GuC */
        context_size += PAGE_SIZE * LRC_PPHWSP_PN;

        ctx_obj = i915_gem_object_create(dev, context_size);
        if (IS_ERR(ctx_obj)) {
                DRM_DEBUG_DRIVER("Alloc LRC backing obj failed.\n");
                return PTR_ERR(ctx_obj);
        }

        ringbuf = intel_engine_create_ringbuffer(engine, 4 * PAGE_SIZE);
        if (IS_ERR(ringbuf)) {
                ret = PTR_ERR(ringbuf);
                goto error_deref_obj;
        }

        ret = populate_lr_context(ctx, ctx_obj, engine, ringbuf);
        if (ret) {
                DRM_DEBUG_DRIVER("Failed to populate LRC: %d\n", ret);
                goto error_ringbuf;
        }

        ctx->engine[engine->id].ringbuf = ringbuf;
        ctx->engine[engine->id].state = ctx_obj;

        if (ctx != ctx->i915->kernel_context && engine->init_context) {
                struct drm_i915_gem_request *req;

                req = i915_gem_request_alloc(engine, ctx);
                if (IS_ERR(req)) {
                        ret = PTR_ERR(req);
                        DRM_ERROR("ring create req: %d\n", ret);
                        goto error_ringbuf;
                }

                ret = engine->init_context(req);
                i915_add_request_no_flush(req);
                if (ret) {
                        DRM_ERROR("ring init context: %d\n",
                                ret);
                        goto error_ringbuf;
                }
        }
        return 0;

error_ringbuf:
        intel_ringbuffer_free(ringbuf);
error_deref_obj:
        drm_gem_object_unreference(&ctx_obj->base);
        ctx->engine[engine->id].ringbuf = NULL;
        ctx->engine[engine->id].state = NULL;
        return ret;
}

void intel_lr_context_reset(struct drm_i915_private *dev_priv,
                            struct intel_context *ctx)
{
        struct intel_engine_cs *engine;

        for_each_engine(engine, dev_priv) {
                struct drm_i915_gem_object *ctx_obj =
                                ctx->engine[engine->id].state;
                struct intel_ringbuffer *ringbuf =
                                ctx->engine[engine->id].ringbuf;
                void *vaddr;
                uint32_t *reg_state;

                if (!ctx_obj)
                        continue;

                vaddr = i915_gem_object_pin_map(ctx_obj);
                if (WARN_ON(IS_ERR(vaddr)))
                        continue;

                reg_state = vaddr + LRC_STATE_PN * PAGE_SIZE;
                ctx_obj->dirty = true;

                reg_state[CTX_RING_HEAD+1] = 0;
                reg_state[CTX_RING_TAIL+1] = 0;

                i915_gem_object_unpin_map(ctx_obj);

                ringbuf->head = 0;
                ringbuf->tail = 0;
        }
}