New driver "sfc" for Solarstorm SFC4000 controller.

[deliverable/linux.git] / drivers / net / sfc / rx.c

/****************************************************************************
 * Driver for Solarflare Solarstorm network controllers and boards
 * Copyright 2005-2006 Fen Systems Ltd.
 * Copyright 2005-2008 Solarflare Communications Inc.
 *
 * This program is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 as published
 * by the Free Software Foundation, incorporated herein by reference.
 */

#include <linux/socket.h>
#include <linux/in.h>
#include <linux/ip.h>
#include <linux/tcp.h>
#include <linux/udp.h>
#include <net/ip.h>
#include <net/checksum.h>
#include "net_driver.h"
#include "rx.h"
#include "efx.h"
#include "falcon.h"
#include "workarounds.h"

/* Number of RX descriptors pushed at once. */
#define EFX_RX_BATCH  8

/* Size of buffer allocated for skb header area. */
#define EFX_SKB_HEADERS  64u

/*
 * rx_alloc_method - RX buffer allocation method
 *
 * This driver supports two methods for allocating and using RX buffers:
 * each RX buffer may be backed by an skb or by an order-n page.
 *
 * When LRO is in use then the second method has a lower overhead,
 * since we don't have to allocate then free skbs on reassembled frames.
 *
 * Values:
 *   - RX_ALLOC_METHOD_AUTO = 0
 *   - RX_ALLOC_METHOD_SKB  = 1
 *   - RX_ALLOC_METHOD_PAGE = 2
 *
 * The heuristic for %RX_ALLOC_METHOD_AUTO is a simple hysteresis count
 * controlled by the parameters below.
 *
 *   - Since pushing and popping descriptors are separated by the rx_queue
 *     size, so the watermarks should be ~rxd_size.
 *   - The performance win by using page-based allocation for LRO is less
 *     than the performance hit of using page-based allocation of non-LRO,
 *     so the watermarks should reflect this.
 *
 * Per channel we maintain a single variable, updated by each channel:
 *
 *   rx_alloc_level += (lro_performed ? RX_ALLOC_FACTOR_LRO :
 *                      RX_ALLOC_FACTOR_SKB)
 * Per NAPI poll interval, we constrain rx_alloc_level to 0..MAX (which
 * limits the hysteresis), and update the allocation strategy:
 *
 *   rx_alloc_method = (rx_alloc_level > RX_ALLOC_LEVEL_LRO ?
 *                      RX_ALLOC_METHOD_PAGE : RX_ALLOC_METHOD_SKB)
 */
static int rx_alloc_method = RX_ALLOC_METHOD_PAGE;

#define RX_ALLOC_LEVEL_LRO 0x2000
#define RX_ALLOC_LEVEL_MAX 0x3000
#define RX_ALLOC_FACTOR_LRO 1
#define RX_ALLOC_FACTOR_SKB (-2)

/* This is the percentage fill level below which new RX descriptors
 * will be added to the RX descriptor ring.
 */
static unsigned int rx_refill_threshold = 90;

/* This is the percentage fill level to which an RX queue will be refilled
 * when the "RX refill threshold" is reached.
 */
static unsigned int rx_refill_limit = 95;

/*
 * RX maximum head room required.
 *
 * This must be at least 1 to prevent overflow and at least 2 to allow
 * pipelined receives.
 */
#define EFX_RXD_HEAD_ROOM 2

/* Macros for zero-order pages (potentially) containing multiple RX buffers */
#define RX_DATA_OFFSET(_data)                           \
        (((unsigned long) (_data)) & (PAGE_SIZE-1))
#define RX_BUF_OFFSET(_rx_buf)                          \
        RX_DATA_OFFSET((_rx_buf)->data)

#define RX_PAGE_SIZE(_efx)                              \
        (PAGE_SIZE * (1u << (_efx)->rx_buffer_order))


/**************************************************************************
 *
 * Linux generic LRO handling
 *
 **************************************************************************
 */

static int efx_lro_get_skb_hdr(struct sk_buff *skb, void **ip_hdr,
                               void **tcpudp_hdr, u64 *hdr_flags, void *priv)
{
        struct efx_channel *channel = (struct efx_channel *)priv;
        struct iphdr *iph;
        struct tcphdr *th;

        iph = (struct iphdr *)skb->data;
        if (skb->protocol != htons(ETH_P_IP) || iph->protocol != IPPROTO_TCP)
                goto fail;

        th = (struct tcphdr *)(skb->data + iph->ihl * 4);

        *tcpudp_hdr = th;
        *ip_hdr = iph;
        *hdr_flags = LRO_IPV4 | LRO_TCP;

        channel->rx_alloc_level += RX_ALLOC_FACTOR_LRO;
        return 0;
fail:
        channel->rx_alloc_level += RX_ALLOC_FACTOR_SKB;
        return -1;
}

static int efx_get_frag_hdr(struct skb_frag_struct *frag, void **mac_hdr,
                            void **ip_hdr, void **tcpudp_hdr, u64 *hdr_flags,
                            void *priv)
{
        struct efx_channel *channel = (struct efx_channel *)priv;
        struct ethhdr *eh;
        struct iphdr *iph;

        /* We support EtherII and VLAN encapsulated IPv4 */
        eh = (struct ethhdr *)(page_address(frag->page) + frag->page_offset);
        *mac_hdr = eh;

        if (eh->h_proto == htons(ETH_P_IP)) {
                iph = (struct iphdr *)(eh + 1);
        } else {
                struct vlan_ethhdr *veh = (struct vlan_ethhdr *)eh;
                if (veh->h_vlan_encapsulated_proto != htons(ETH_P_IP))
                        goto fail;

                iph = (struct iphdr *)(veh + 1);
        }
        *ip_hdr = iph;

        /* We can only do LRO over TCP */
        if (iph->protocol != IPPROTO_TCP)
                goto fail;

        *hdr_flags = LRO_IPV4 | LRO_TCP;
        *tcpudp_hdr = (struct tcphdr *)((u8 *) iph + iph->ihl * 4);

        channel->rx_alloc_level += RX_ALLOC_FACTOR_LRO;
        return 0;
 fail:
        channel->rx_alloc_level += RX_ALLOC_FACTOR_SKB;
        return -1;
}

int efx_lro_init(struct net_lro_mgr *lro_mgr, struct efx_nic *efx)
{
        size_t s = sizeof(struct net_lro_desc) * EFX_MAX_LRO_DESCRIPTORS;
        struct net_lro_desc *lro_arr;

        /* Allocate the LRO descriptors structure */
        lro_arr = kzalloc(s, GFP_KERNEL);
        if (lro_arr == NULL)
                return -ENOMEM;

        lro_mgr->lro_arr = lro_arr;
        lro_mgr->max_desc = EFX_MAX_LRO_DESCRIPTORS;
        lro_mgr->max_aggr = EFX_MAX_LRO_AGGR;
        lro_mgr->frag_align_pad = EFX_PAGE_SKB_ALIGN;

        lro_mgr->get_skb_header = efx_lro_get_skb_hdr;
        lro_mgr->get_frag_header = efx_get_frag_hdr;
        lro_mgr->dev = efx->net_dev;

        lro_mgr->features = LRO_F_NAPI;

        /* We can pass packets up with the checksum intact */
        lro_mgr->ip_summed = CHECKSUM_UNNECESSARY;

        lro_mgr->ip_summed_aggr = CHECKSUM_UNNECESSARY;

        return 0;
}

void efx_lro_fini(struct net_lro_mgr *lro_mgr)
{
        kfree(lro_mgr->lro_arr);
        lro_mgr->lro_arr = NULL;
}

/**
 * efx_init_rx_buffer_skb - create new RX buffer using skb-based allocation
 *
 * @rx_queue:           Efx RX queue
 * @rx_buf:             RX buffer structure to populate
 *
 * This allocates memory for a new receive buffer, maps it for DMA,
 * and populates a struct efx_rx_buffer with the relevant
 * information.  Return a negative error code or 0 on success.
 */
static inline int efx_init_rx_buffer_skb(struct efx_rx_queue *rx_queue,
                                         struct efx_rx_buffer *rx_buf)
{
        struct efx_nic *efx = rx_queue->efx;
        struct net_device *net_dev = efx->net_dev;
        int skb_len = efx->rx_buffer_len;

        rx_buf->skb = netdev_alloc_skb(net_dev, skb_len);
        if (unlikely(!rx_buf->skb))
                return -ENOMEM;

        /* Adjust the SKB for padding and checksum */
        skb_reserve(rx_buf->skb, NET_IP_ALIGN);
        rx_buf->len = skb_len - NET_IP_ALIGN;
        rx_buf->data = (char *)rx_buf->skb->data;
        rx_buf->skb->ip_summed = CHECKSUM_UNNECESSARY;

        rx_buf->dma_addr = pci_map_single(efx->pci_dev,
                                          rx_buf->data, rx_buf->len,
                                          PCI_DMA_FROMDEVICE);

        if (unlikely(pci_dma_mapping_error(rx_buf->dma_addr))) {
                dev_kfree_skb_any(rx_buf->skb);
                rx_buf->skb = NULL;
                return -EIO;
        }

        return 0;
}

/**
 * efx_init_rx_buffer_page - create new RX buffer using page-based allocation
 *
 * @rx_queue:           Efx RX queue
 * @rx_buf:             RX buffer structure to populate
 *
 * This allocates memory for a new receive buffer, maps it for DMA,
 * and populates a struct efx_rx_buffer with the relevant
 * information.  Return a negative error code or 0 on success.
 */
static inline int efx_init_rx_buffer_page(struct efx_rx_queue *rx_queue,
                                          struct efx_rx_buffer *rx_buf)
{
        struct efx_nic *efx = rx_queue->efx;
        int bytes, space, offset;

        bytes = efx->rx_buffer_len - EFX_PAGE_IP_ALIGN;

        /* If there is space left in the previously allocated page,
         * then use it. Otherwise allocate a new one */
        rx_buf->page = rx_queue->buf_page;
        if (rx_buf->page == NULL) {
                dma_addr_t dma_addr;

                rx_buf->page = alloc_pages(__GFP_COLD | __GFP_COMP | GFP_ATOMIC,
                                           efx->rx_buffer_order);
                if (unlikely(rx_buf->page == NULL))
                        return -ENOMEM;

                dma_addr = pci_map_page(efx->pci_dev, rx_buf->page,
                                        0, RX_PAGE_SIZE(efx),
                                        PCI_DMA_FROMDEVICE);

                if (unlikely(pci_dma_mapping_error(dma_addr))) {
                        __free_pages(rx_buf->page, efx->rx_buffer_order);
                        rx_buf->page = NULL;
                        return -EIO;
                }

                rx_queue->buf_page = rx_buf->page;
                rx_queue->buf_dma_addr = dma_addr;
                rx_queue->buf_data = ((char *) page_address(rx_buf->page) +
                                      EFX_PAGE_IP_ALIGN);
        }

        offset = RX_DATA_OFFSET(rx_queue->buf_data);
        rx_buf->len = bytes;
        rx_buf->dma_addr = rx_queue->buf_dma_addr + offset;
        rx_buf->data = rx_queue->buf_data;

        /* Try to pack multiple buffers per page */
        if (efx->rx_buffer_order == 0) {
                /* The next buffer starts on the next 512 byte boundary */
                rx_queue->buf_data += ((bytes + 0x1ff) & ~0x1ff);
                offset += ((bytes + 0x1ff) & ~0x1ff);

                space = RX_PAGE_SIZE(efx) - offset;
                if (space >= bytes) {
                        /* Refs dropped on kernel releasing each skb */
                        get_page(rx_queue->buf_page);
                        goto out;
                }
        }

        /* This is the final RX buffer for this page, so mark it for
         * unmapping */
        rx_queue->buf_page = NULL;
        rx_buf->unmap_addr = rx_queue->buf_dma_addr;

 out:
        return 0;
}

/* This allocates memory for a new receive buffer, maps it for DMA,
 * and populates a struct efx_rx_buffer with the relevant
 * information.
 */
static inline int efx_init_rx_buffer(struct efx_rx_queue *rx_queue,
                                     struct efx_rx_buffer *new_rx_buf)
{
        int rc = 0;

        if (rx_queue->channel->rx_alloc_push_pages) {
                new_rx_buf->skb = NULL;
                rc = efx_init_rx_buffer_page(rx_queue, new_rx_buf);
                rx_queue->alloc_page_count++;
        } else {
                new_rx_buf->page = NULL;
                rc = efx_init_rx_buffer_skb(rx_queue, new_rx_buf);
                rx_queue->alloc_skb_count++;
        }

        if (unlikely(rc < 0))
                EFX_LOG_RL(rx_queue->efx, "%s RXQ[%d] =%d\n", __func__,
                           rx_queue->queue, rc);
        return rc;
}

static inline void efx_unmap_rx_buffer(struct efx_nic *efx,
                                       struct efx_rx_buffer *rx_buf)
{
        if (rx_buf->page) {
                EFX_BUG_ON_PARANOID(rx_buf->skb);
                if (rx_buf->unmap_addr) {
                        pci_unmap_page(efx->pci_dev, rx_buf->unmap_addr,
                                       RX_PAGE_SIZE(efx), PCI_DMA_FROMDEVICE);
                        rx_buf->unmap_addr = 0;
                }
        } else if (likely(rx_buf->skb)) {
                pci_unmap_single(efx->pci_dev, rx_buf->dma_addr,
                                 rx_buf->len, PCI_DMA_FROMDEVICE);
        }
}

static inline void efx_free_rx_buffer(struct efx_nic *efx,
                                      struct efx_rx_buffer *rx_buf)
{
        if (rx_buf->page) {
                __free_pages(rx_buf->page, efx->rx_buffer_order);
                rx_buf->page = NULL;
        } else if (likely(rx_buf->skb)) {
                dev_kfree_skb_any(rx_buf->skb);
                rx_buf->skb = NULL;
        }
}

static inline void efx_fini_rx_buffer(struct efx_rx_queue *rx_queue,
                                      struct efx_rx_buffer *rx_buf)
{
        efx_unmap_rx_buffer(rx_queue->efx, rx_buf);
        efx_free_rx_buffer(rx_queue->efx, rx_buf);
}

/**
 * efx_fast_push_rx_descriptors - push new RX descriptors quickly
 * @rx_queue:           RX descriptor queue
 * @retry:              Recheck the fill level
 * This will aim to fill the RX descriptor queue up to
 * @rx_queue->@fast_fill_limit. If there is insufficient atomic
 * memory to do so, the caller should retry.
 */
static int __efx_fast_push_rx_descriptors(struct efx_rx_queue *rx_queue,
                                          int retry)
{
        struct efx_rx_buffer *rx_buf;
        unsigned fill_level, index;
        int i, space, rc = 0;

        /* Calculate current fill level.  Do this outside the lock,
         * because most of the time we'll end up not wanting to do the
         * fill anyway.
         */
        fill_level = (rx_queue->added_count - rx_queue->removed_count);
        EFX_BUG_ON_PARANOID(fill_level >
                            rx_queue->efx->type->rxd_ring_mask + 1);

        /* Don't fill if we don't need to */
        if (fill_level >= rx_queue->fast_fill_trigger)
                return 0;

        /* Record minimum fill level */
        if (unlikely(fill_level < rx_queue->min_fill))
                if (fill_level)
                        rx_queue->min_fill = fill_level;

        /* Acquire RX add lock.  If this lock is contended, then a fast
         * fill must already be in progress (e.g. in the refill
         * tasklet), so we don't need to do anything
         */
        if (!spin_trylock_bh(&rx_queue->add_lock))
                return -1;

 retry:
        /* Recalculate current fill level now that we have the lock */
        fill_level = (rx_queue->added_count - rx_queue->removed_count);
        EFX_BUG_ON_PARANOID(fill_level >
                            rx_queue->efx->type->rxd_ring_mask + 1);
        space = rx_queue->fast_fill_limit - fill_level;
        if (space < EFX_RX_BATCH)
                goto out_unlock;

        EFX_TRACE(rx_queue->efx, "RX queue %d fast-filling descriptor ring from"
                  " level %d to level %d using %s allocation\n",
                  rx_queue->queue, fill_level, rx_queue->fast_fill_limit,
                  rx_queue->channel->rx_alloc_push_pages ? "page" : "skb");

        do {
                for (i = 0; i < EFX_RX_BATCH; ++i) {
                        index = (rx_queue->added_count &
                                 rx_queue->efx->type->rxd_ring_mask);
                        rx_buf = efx_rx_buffer(rx_queue, index);
                        rc = efx_init_rx_buffer(rx_queue, rx_buf);
                        if (unlikely(rc))
                                goto out;
                        ++rx_queue->added_count;
                }
        } while ((space -= EFX_RX_BATCH) >= EFX_RX_BATCH);

        EFX_TRACE(rx_queue->efx, "RX queue %d fast-filled descriptor ring "
                  "to level %d\n", rx_queue->queue,
                  rx_queue->added_count - rx_queue->removed_count);

 out:
        /* Send write pointer to card. */
        falcon_notify_rx_desc(rx_queue);

        /* If the fast fill is running inside from the refill tasklet, then
         * for SMP systems it may be running on a different CPU to
         * RX event processing, which means that the fill level may now be
         * out of date. */
        if (unlikely(retry && (rc == 0)))
                goto retry;

 out_unlock:
        spin_unlock_bh(&rx_queue->add_lock);

        return rc;
}

/**
 * efx_fast_push_rx_descriptors - push new RX descriptors quickly
 * @rx_queue:           RX descriptor queue
 *
 * This will aim to fill the RX descriptor queue up to
 * @rx_queue->@fast_fill_limit.  If there is insufficient memory to do so,
 * it will schedule a work item to immediately continue the fast fill
 */
void efx_fast_push_rx_descriptors(struct efx_rx_queue *rx_queue)
{
        int rc;

        rc = __efx_fast_push_rx_descriptors(rx_queue, 0);
        if (unlikely(rc)) {
                /* Schedule the work item to run immediately. The hope is
                 * that work is immediately pending to free some memory
                 * (e.g. an RX event or TX completion)
                 */
                efx_schedule_slow_fill(rx_queue, 0);
        }
}

void efx_rx_work(struct work_struct *data)
{
        struct efx_rx_queue *rx_queue;
        int rc;

        rx_queue = container_of(data, struct efx_rx_queue, work.work);

        if (unlikely(!rx_queue->channel->enabled))
                return;

        EFX_TRACE(rx_queue->efx, "RX queue %d worker thread executing on CPU "
                  "%d\n", rx_queue->queue, raw_smp_processor_id());

        ++rx_queue->slow_fill_count;
        /* Push new RX descriptors, allowing at least 1 jiffy for
         * the kernel to free some more memory. */
        rc = __efx_fast_push_rx_descriptors(rx_queue, 1);
        if (rc)
                efx_schedule_slow_fill(rx_queue, 1);
}

static inline void efx_rx_packet__check_len(struct efx_rx_queue *rx_queue,
                                            struct efx_rx_buffer *rx_buf,
                                            int len, int *discard,
                                            int *leak_packet)
{
        struct efx_nic *efx = rx_queue->efx;
        unsigned max_len = rx_buf->len - efx->type->rx_buffer_padding;

        if (likely(len <= max_len))
                return;

        /* The packet must be discarded, but this is only a fatal error
         * if the caller indicated it was
         */
        *discard = 1;

        if ((len > rx_buf->len) && EFX_WORKAROUND_8071(efx)) {
                EFX_ERR_RL(efx, " RX queue %d seriously overlength "
                           "RX event (0x%x > 0x%x+0x%x). Leaking\n",
                           rx_queue->queue, len, max_len,
                           efx->type->rx_buffer_padding);
                /* If this buffer was skb-allocated, then the meta
                 * data at the end of the skb will be trashed. So
                 * we have no choice but to leak the fragment.
                 */
                *leak_packet = (rx_buf->skb != NULL);
                efx_schedule_reset(efx, RESET_TYPE_RX_RECOVERY);
        } else {
                EFX_ERR_RL(efx, " RX queue %d overlength RX event "
                           "(0x%x > 0x%x)\n", rx_queue->queue, len, max_len);
        }

        rx_queue->channel->n_rx_overlength++;
}

/* Pass a received packet up through the generic LRO stack
 *
 * Handles driverlink veto, and passes the fragment up via
 * the appropriate LRO method
 */
static inline void efx_rx_packet_lro(struct efx_channel *channel,
                                     struct efx_rx_buffer *rx_buf)
{
        struct net_lro_mgr *lro_mgr = &channel->lro_mgr;
        void *priv = channel;

        /* Pass the skb/page into the LRO engine */
        if (rx_buf->page) {
                struct skb_frag_struct frags;

                frags.page = rx_buf->page;
                frags.page_offset = RX_BUF_OFFSET(rx_buf);
                frags.size = rx_buf->len;

                lro_receive_frags(lro_mgr, &frags, rx_buf->len,
                                  rx_buf->len, priv, 0);

                EFX_BUG_ON_PARANOID(rx_buf->skb);
                rx_buf->page = NULL;
        } else {
                EFX_BUG_ON_PARANOID(!rx_buf->skb);

                lro_receive_skb(lro_mgr, rx_buf->skb, priv);
                rx_buf->skb = NULL;
        }
}

/* Allocate and construct an SKB around a struct page.*/
static inline struct sk_buff *efx_rx_mk_skb(struct efx_rx_buffer *rx_buf,
                                            struct efx_nic *efx,
                                            int hdr_len)
{
        struct sk_buff *skb;

        /* Allocate an SKB to store the headers */
        skb = netdev_alloc_skb(efx->net_dev, hdr_len + EFX_PAGE_SKB_ALIGN);
        if (unlikely(skb == NULL)) {
                EFX_ERR_RL(efx, "RX out of memory for skb\n");
                return NULL;
        }

        EFX_BUG_ON_PARANOID(skb_shinfo(skb)->nr_frags);
        EFX_BUG_ON_PARANOID(rx_buf->len < hdr_len);

        skb->ip_summed = CHECKSUM_UNNECESSARY;
        skb_reserve(skb, EFX_PAGE_SKB_ALIGN);

        skb->len = rx_buf->len;
        skb->truesize = rx_buf->len + sizeof(struct sk_buff);
        memcpy(skb->data, rx_buf->data, hdr_len);
        skb->tail += hdr_len;

        /* Append the remaining page onto the frag list */
        if (unlikely(rx_buf->len > hdr_len)) {
                struct skb_frag_struct *frag = skb_shinfo(skb)->frags;
                frag->page = rx_buf->page;
                frag->page_offset = RX_BUF_OFFSET(rx_buf) + hdr_len;
                frag->size = skb->len - hdr_len;
                skb_shinfo(skb)->nr_frags = 1;
                skb->data_len = frag->size;
        } else {
                __free_pages(rx_buf->page, efx->rx_buffer_order);
                skb->data_len = 0;
        }

        /* Ownership has transferred from the rx_buf to skb */
        rx_buf->page = NULL;

        /* Move past the ethernet header */
        skb->protocol = eth_type_trans(skb, efx->net_dev);

        return skb;
}

void efx_rx_packet(struct efx_rx_queue *rx_queue, unsigned int index,
                   unsigned int len, int checksummed, int discard)
{
        struct efx_nic *efx = rx_queue->efx;
        struct efx_rx_buffer *rx_buf;
        int leak_packet = 0;

        rx_buf = efx_rx_buffer(rx_queue, index);
        EFX_BUG_ON_PARANOID(!rx_buf->data);
        EFX_BUG_ON_PARANOID(rx_buf->skb && rx_buf->page);
        EFX_BUG_ON_PARANOID(!(rx_buf->skb || rx_buf->page));

        /* This allows the refill path to post another buffer.
         * EFX_RXD_HEAD_ROOM ensures that the slot we are using
         * isn't overwritten yet.
         */
        rx_queue->removed_count++;

        /* Validate the length encoded in the event vs the descriptor pushed */
        efx_rx_packet__check_len(rx_queue, rx_buf, len,
                                 &discard, &leak_packet);

        EFX_TRACE(efx, "RX queue %d received id %x at %llx+%x %s%s\n",
                  rx_queue->queue, index,
                  (unsigned long long)rx_buf->dma_addr, len,
                  (checksummed ? " [SUMMED]" : ""),
                  (discard ? " [DISCARD]" : ""));

        /* Discard packet, if instructed to do so */
        if (unlikely(discard)) {
                if (unlikely(leak_packet))
                        rx_queue->channel->n_skbuff_leaks++;
                else
                        /* We haven't called efx_unmap_rx_buffer yet,
                         * so fini the entire rx_buffer here */
                        efx_fini_rx_buffer(rx_queue, rx_buf);
                return;
        }

        /* Release card resources - assumes all RX buffers consumed in-order
         * per RX queue
         */
        efx_unmap_rx_buffer(efx, rx_buf);

        /* Prefetch nice and early so data will (hopefully) be in cache by
         * the time we look at it.
         */
        prefetch(rx_buf->data);

        /* Pipeline receives so that we give time for packet headers to be
         * prefetched into cache.
         */
        rx_buf->len = len;
        if (rx_queue->channel->rx_pkt)
                __efx_rx_packet(rx_queue->channel,
                                rx_queue->channel->rx_pkt,
                                rx_queue->channel->rx_pkt_csummed);
        rx_queue->channel->rx_pkt = rx_buf;
        rx_queue->channel->rx_pkt_csummed = checksummed;
}

/* Handle a received packet.  Second half: Touches packet payload. */
void __efx_rx_packet(struct efx_channel *channel,
                     struct efx_rx_buffer *rx_buf, int checksummed)
{
        struct efx_nic *efx = channel->efx;
        struct sk_buff *skb;
        int lro = efx->net_dev->features & NETIF_F_LRO;

        if (rx_buf->skb) {
                prefetch(skb_shinfo(rx_buf->skb));

                skb_put(rx_buf->skb, rx_buf->len);

                /* Move past the ethernet header. rx_buf->data still points
                 * at the ethernet header */
                rx_buf->skb->protocol = eth_type_trans(rx_buf->skb,
                                                       efx->net_dev);
        }

        /* Both our generic-LRO and SFC-SSR support skb and page based
         * allocation, but neither support switching from one to the
         * other on the fly. If we spot that the allocation mode has
         * changed, then flush the LRO state.
         */
        if (unlikely(channel->rx_alloc_pop_pages != (rx_buf->page != NULL))) {
                efx_flush_lro(channel);
                channel->rx_alloc_pop_pages = (rx_buf->page != NULL);
        }
        if (likely(checksummed && lro)) {
                efx_rx_packet_lro(channel, rx_buf);
                goto done;
        }

        /* Form an skb if required */
        if (rx_buf->page) {
                int hdr_len = min(rx_buf->len, EFX_SKB_HEADERS);
                skb = efx_rx_mk_skb(rx_buf, efx, hdr_len);
                if (unlikely(skb == NULL)) {
                        efx_free_rx_buffer(efx, rx_buf);
                        goto done;
                }
        } else {
                /* We now own the SKB */
                skb = rx_buf->skb;
                rx_buf->skb = NULL;
        }

        EFX_BUG_ON_PARANOID(rx_buf->page);
        EFX_BUG_ON_PARANOID(rx_buf->skb);
        EFX_BUG_ON_PARANOID(!skb);

        /* Set the SKB flags */
        if (unlikely(!checksummed || !efx->rx_checksum_enabled))
                skb->ip_summed = CHECKSUM_NONE;

        /* Pass the packet up */
        netif_receive_skb(skb);

        /* Update allocation strategy method */
        channel->rx_alloc_level += RX_ALLOC_FACTOR_SKB;

        /* fall-thru */
done:
        efx->net_dev->last_rx = jiffies;
}

void efx_rx_strategy(struct efx_channel *channel)
{
        enum efx_rx_alloc_method method = rx_alloc_method;

        /* Only makes sense to use page based allocation if LRO is enabled */
        if (!(channel->efx->net_dev->features & NETIF_F_LRO)) {
                method = RX_ALLOC_METHOD_SKB;
        } else if (method == RX_ALLOC_METHOD_AUTO) {
                /* Constrain the rx_alloc_level */
                if (channel->rx_alloc_level < 0)
                        channel->rx_alloc_level = 0;
                else if (channel->rx_alloc_level > RX_ALLOC_LEVEL_MAX)
                        channel->rx_alloc_level = RX_ALLOC_LEVEL_MAX;

                /* Decide on the allocation method */
                method = ((channel->rx_alloc_level > RX_ALLOC_LEVEL_LRO) ?
                          RX_ALLOC_METHOD_PAGE : RX_ALLOC_METHOD_SKB);
        }

        /* Push the option */
        channel->rx_alloc_push_pages = (method == RX_ALLOC_METHOD_PAGE);
}

int efx_probe_rx_queue(struct efx_rx_queue *rx_queue)
{
        struct efx_nic *efx = rx_queue->efx;
        unsigned int rxq_size;
        int rc;

        EFX_LOG(efx, "creating RX queue %d\n", rx_queue->queue);

        /* Allocate RX buffers */
        rxq_size = (efx->type->rxd_ring_mask + 1) * sizeof(*rx_queue->buffer);
        rx_queue->buffer = kzalloc(rxq_size, GFP_KERNEL);
        if (!rx_queue->buffer) {
                rc = -ENOMEM;
                goto fail1;
        }

        rc = falcon_probe_rx(rx_queue);
        if (rc)
                goto fail2;

        return 0;

 fail2:
        kfree(rx_queue->buffer);
        rx_queue->buffer = NULL;
 fail1:
        rx_queue->used = 0;

        return rc;
}

int efx_init_rx_queue(struct efx_rx_queue *rx_queue)
{
        struct efx_nic *efx = rx_queue->efx;
        unsigned int max_fill, trigger, limit;

        EFX_LOG(rx_queue->efx, "initialising RX queue %d\n", rx_queue->queue);

        /* Initialise ptr fields */
        rx_queue->added_count = 0;
        rx_queue->notified_count = 0;
        rx_queue->removed_count = 0;
        rx_queue->min_fill = -1U;
        rx_queue->min_overfill = -1U;

        /* Initialise limit fields */
        max_fill = efx->type->rxd_ring_mask + 1 - EFX_RXD_HEAD_ROOM;
        trigger = max_fill * min(rx_refill_threshold, 100U) / 100U;
        limit = max_fill * min(rx_refill_limit, 100U) / 100U;

        rx_queue->max_fill = max_fill;
        rx_queue->fast_fill_trigger = trigger;
        rx_queue->fast_fill_limit = limit;

        /* Set up RX descriptor ring */
        return falcon_init_rx(rx_queue);
}

void efx_fini_rx_queue(struct efx_rx_queue *rx_queue)
{
        int i;
        struct efx_rx_buffer *rx_buf;

        EFX_LOG(rx_queue->efx, "shutting down RX queue %d\n", rx_queue->queue);

        falcon_fini_rx(rx_queue);

        /* Release RX buffers NB start at index 0 not current HW ptr */
        if (rx_queue->buffer) {
                for (i = 0; i <= rx_queue->efx->type->rxd_ring_mask; i++) {
                        rx_buf = efx_rx_buffer(rx_queue, i);
                        efx_fini_rx_buffer(rx_queue, rx_buf);
                }
        }

        /* For a page that is part-way through splitting into RX buffers */
        if (rx_queue->buf_page != NULL) {
                pci_unmap_page(rx_queue->efx->pci_dev, rx_queue->buf_dma_addr,
                               RX_PAGE_SIZE(rx_queue->efx), PCI_DMA_FROMDEVICE);
                __free_pages(rx_queue->buf_page,
                             rx_queue->efx->rx_buffer_order);
                rx_queue->buf_page = NULL;
        }
}

void efx_remove_rx_queue(struct efx_rx_queue *rx_queue)
{
        EFX_LOG(rx_queue->efx, "destroying RX queue %d\n", rx_queue->queue);

        falcon_remove_rx(rx_queue);

        kfree(rx_queue->buffer);
        rx_queue->buffer = NULL;
        rx_queue->used = 0;
}

void efx_flush_lro(struct efx_channel *channel)
{
        lro_flush_all(&channel->lro_mgr);
}


module_param(rx_alloc_method, int, 0644);
MODULE_PARM_DESC(rx_alloc_method, "Allocation method used for RX buffers");

module_param(rx_refill_threshold, uint, 0444);
MODULE_PARM_DESC(rx_refill_threshold,
                 "RX descriptor ring fast/slow fill threshold (%)");