[deliverable/linux.git] / drivers / gpu / drm / i915 / i915_gem_stolen.c

/*
 * Copyright © 2008-2012 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:
 *    Eric Anholt <eric@anholt.net>
 *    Chris Wilson <chris@chris-wilson.co.uk>
 *
 */

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

/*
 * The BIOS typically reserves some of the system's memory for the exclusive
 * use of the integrated graphics. This memory is no longer available for
 * use by the OS and so the user finds that his system has less memory
 * available than he put in. We refer to this memory as stolen.
 *
 * The BIOS will allocate its framebuffer from the stolen memory. Our
 * goal is try to reuse that object for our own fbcon which must always
 * be available for panics. Anything else we can reuse the stolen memory
 * for is a boon.
 */

static unsigned long i915_stolen_to_physical(struct drm_device *dev)
{
	struct drm_i915_private *dev_priv = dev->dev_private;
	struct pci_dev *pdev = dev_priv->bridge_dev;
	u32 base;

	/* On the machines I have tested the Graphics Base of Stolen Memory
	 * is unreliable, so on those compute the base by subtracting the
	 * stolen memory from the Top of Low Usable DRAM which is where the
	 * BIOS places the graphics stolen memory.
	 *
	 * On gen2, the layout is slightly different with the Graphics Segment
	 * immediately following Top of Memory (or Top of Usable DRAM). Note
	 * it appears that TOUD is only reported by 865g, so we just use the
	 * top of memory as determined by the e820 probe.
	 *
	 * XXX gen2 requires an unavailable symbol and 945gm fails with
	 * its value of TOLUD.
	 */
	base = 0;
	if (INTEL_INFO(dev)->gen >= 6) {
		/* Read Base Data of Stolen Memory Register (BDSM) directly.
		 * Note that there is also a MCHBAR miror at 0x1080c0 or
		 * we could use device 2:0x5c instead.
		*/
		pci_read_config_dword(pdev, 0xB0, &base);
		base &= ~4095; /* lower bits used for locking register */
	} else if (INTEL_INFO(dev)->gen > 3 || IS_G33(dev)) {
		/* Read Graphics Base of Stolen Memory directly */
		pci_read_config_dword(pdev, 0xA4, &base);
#if 0
	} else if (IS_GEN3(dev)) {
		u8 val;
		/* Stolen is immediately below Top of Low Usable DRAM */
		pci_read_config_byte(pdev, 0x9c, &val);
		base = val >> 3 << 27;
		base -= dev_priv->mm.gtt->stolen_size;
	} else {
		/* Stolen is immediately above Top of Memory */
		base = max_low_pfn_mapped << PAGE_SHIFT;
#endif
	}

	return base;
}

static int i915_setup_compression(struct drm_device *dev, int size)
{
	struct drm_i915_private *dev_priv = dev->dev_private;
	struct drm_mm_node *compressed_fb, *uninitialized_var(compressed_llb);

	/* Try to over-allocate to reduce reallocations and fragmentation */
	compressed_fb = drm_mm_search_free(&dev_priv->mm.stolen,
					   size <<= 1, 4096, 0);
	if (!compressed_fb)
		compressed_fb = drm_mm_search_free(&dev_priv->mm.stolen,
						   size >>= 1, 4096, 0);
	if (compressed_fb)
		compressed_fb = drm_mm_get_block(compressed_fb, size, 4096);
	if (!compressed_fb)
		goto err;

	if (HAS_PCH_SPLIT(dev))
		I915_WRITE(ILK_DPFC_CB_BASE, compressed_fb->start);
	else if (IS_GM45(dev)) {
		I915_WRITE(DPFC_CB_BASE, compressed_fb->start);
	} else {
		compressed_llb = drm_mm_search_free(&dev_priv->mm.stolen,
						    4096, 4096, 0);
		if (compressed_llb)
			compressed_llb = drm_mm_get_block(compressed_llb,
							  4096, 4096);
		if (!compressed_llb)
			goto err_fb;

		dev_priv->compressed_llb = compressed_llb;

		I915_WRITE(FBC_CFB_BASE,
			   dev_priv->mm.stolen_base + compressed_fb->start);
		I915_WRITE(FBC_LL_BASE,
			   dev_priv->mm.stolen_base + compressed_llb->start);
	}

	dev_priv->compressed_fb = compressed_fb;
	dev_priv->cfb_size = size;

	DRM_DEBUG_KMS("reserved %d bytes of contiguous stolen space for FBC\n",
		      size);

	return 0;

err_fb:
	drm_mm_put_block(compressed_fb);
err:
	return -ENOSPC;
}

int i915_gem_stolen_setup_compression(struct drm_device *dev, int size)
{
	struct drm_i915_private *dev_priv = dev->dev_private;

	if (dev_priv->mm.stolen_base == 0)
		return -ENODEV;

	if (size < dev_priv->cfb_size)
		return 0;

	/* Release any current block */
	i915_gem_stolen_cleanup_compression(dev);

	return i915_setup_compression(dev, size);
}

void i915_gem_stolen_cleanup_compression(struct drm_device *dev)
{
	struct drm_i915_private *dev_priv = dev->dev_private;

	if (dev_priv->cfb_size == 0)
		return;

	if (dev_priv->compressed_fb)
		drm_mm_put_block(dev_priv->compressed_fb);

	if (dev_priv->compressed_llb)
		drm_mm_put_block(dev_priv->compressed_llb);

	dev_priv->cfb_size = 0;
}

void i915_gem_cleanup_stolen(struct drm_device *dev)
{
	struct drm_i915_private *dev_priv = dev->dev_private;

	i915_gem_stolen_cleanup_compression(dev);
	drm_mm_takedown(&dev_priv->mm.stolen);
}

int i915_gem_init_stolen(struct drm_device *dev)
{
	struct drm_i915_private *dev_priv = dev->dev_private;

	dev_priv->mm.stolen_base = i915_stolen_to_physical(dev);
	if (dev_priv->mm.stolen_base == 0)
		return 0;

	DRM_DEBUG_KMS("found %zd bytes of stolen memory at %08lx\n",
		      dev_priv->gtt.stolen_size, dev_priv->mm.stolen_base);

	/* Basic memrange allocator for stolen space */
	drm_mm_init(&dev_priv->mm.stolen, 0, dev_priv->gtt.stolen_size);

	return 0;
}

static struct sg_table *
i915_pages_create_for_stolen(struct drm_device *dev,
			     u32 offset, u32 size)
{
	struct drm_i915_private *dev_priv = dev->dev_private;
	struct sg_table *st;
	struct scatterlist *sg;

	DRM_DEBUG_DRIVER("offset=0x%x, size=%d\n", offset, size);
	BUG_ON(offset > dev_priv->gtt.stolen_size - size);

	/* We hide that we have no struct page backing our stolen object
	 * by wrapping the contiguous physical allocation with a fake
	 * dma mapping in a single scatterlist.
	 */

	st = kmalloc(sizeof(*st), GFP_KERNEL);
	if (st == NULL)
		return NULL;

	if (sg_alloc_table(st, 1, GFP_KERNEL)) {
		kfree(st);
		return NULL;
	}

	sg = st->sgl;
	/* we set the dummy page here only to make for_each_sg_page work */
	sg_set_page(sg, dev_priv->gtt.scratch_page, size, offset);

	sg_dma_address(sg) = (dma_addr_t)dev_priv->mm.stolen_base + offset;
	sg_dma_len(sg) = size;

	return st;
}

static int i915_gem_object_get_pages_stolen(struct drm_i915_gem_object *obj)
{
	BUG();
	return -EINVAL;
}

static void i915_gem_object_put_pages_stolen(struct drm_i915_gem_object *obj)
{
	/* Should only be called during free */
	sg_free_table(obj->pages);
	kfree(obj->pages);
}

static const struct drm_i915_gem_object_ops i915_gem_object_stolen_ops = {
	.get_pages = i915_gem_object_get_pages_stolen,
	.put_pages = i915_gem_object_put_pages_stolen,
};

static struct drm_i915_gem_object *
_i915_gem_object_create_stolen(struct drm_device *dev,
			       struct drm_mm_node *stolen)
{
	struct drm_i915_gem_object *obj;

	obj = i915_gem_object_alloc(dev);
	if (obj == NULL)
		return NULL;

	if (drm_gem_private_object_init(dev, &obj->base, stolen->size))
		goto cleanup;

	i915_gem_object_init(obj, &i915_gem_object_stolen_ops);

	obj->pages = i915_pages_create_for_stolen(dev,
						  stolen->start, stolen->size);
	if (obj->pages == NULL)
		goto cleanup;

	obj->has_dma_mapping = true;
	obj->pages_pin_count = 1;
	obj->stolen = stolen;

	obj->base.write_domain = I915_GEM_DOMAIN_GTT;
	obj->base.read_domains = I915_GEM_DOMAIN_GTT;
	obj->cache_level = I915_CACHE_NONE;

	return obj;

cleanup:
	i915_gem_object_free(obj);
	return NULL;
}

struct drm_i915_gem_object *
i915_gem_object_create_stolen(struct drm_device *dev, u32 size)
{
	struct drm_i915_private *dev_priv = dev->dev_private;
	struct drm_i915_gem_object *obj;
	struct drm_mm_node *stolen;

	if (dev_priv->mm.stolen_base == 0)
		return NULL;

	DRM_DEBUG_KMS("creating stolen object: size=%x\n", size);
	if (size == 0)
		return NULL;

	stolen = drm_mm_search_free(&dev_priv->mm.stolen, size, 4096, 0);
	if (stolen)
		stolen = drm_mm_get_block(stolen, size, 4096);
	if (stolen == NULL)
		return NULL;

	obj = _i915_gem_object_create_stolen(dev, stolen);
	if (obj)
		return obj;

	drm_mm_put_block(stolen);
	return NULL;
}

void
i915_gem_object_release_stolen(struct drm_i915_gem_object *obj)
{
	if (obj->stolen) {
		drm_mm_put_block(obj->stolen);
		obj->stolen = NULL;
	}
}
Commit	Line	Data
9797fbfb CW	1	/*
	2	* Copyright © 2008-2012 Intel Corporation
	3	*
	4	* Permission is hereby granted, free of charge, to any person obtaining a
	5	* copy of this software and associated documentation files (the "Software"),
	6	* to deal in the Software without restriction, including without limitation
	7	* the rights to use, copy, modify, merge, publish, distribute, sublicense,
	8	* and/or sell copies of the Software, and to permit persons to whom the
	9	* Software is furnished to do so, subject to the following conditions:
	10	*
	11	* The above copyright notice and this permission notice (including the next
	12	* paragraph) shall be included in all copies or substantial portions of the
	13	* Software.
	14	*
	15	* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
	16	* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
	17	* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
	18	* THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
	19	* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
	20	* FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
	21	* IN THE SOFTWARE.
	22	*
	23	* Authors:
	24	* Eric Anholt <eric@anholt.net>
	25	* Chris Wilson <chris@chris-wilson.co.uk>
	26	*
	27	*/
	28
760285e7 DH	29	#include <drm/drmP.h>
760285e7 DH	30	#include <drm/i915_drm.h>
9797fbfb CW	31	#include "i915_drv.h"
	32
	33	/*
	34	* The BIOS typically reserves some of the system's memory for the exclusive
	35	* use of the integrated graphics. This memory is no longer available for
	36	* use by the OS and so the user finds that his system has less memory
	37	* available than he put in. We refer to this memory as stolen.
	38	*
	39	* The BIOS will allocate its framebuffer from the stolen memory. Our
	40	* goal is try to reuse that object for our own fbcon which must always
	41	* be available for panics. Anything else we can reuse the stolen memory
	42	* for is a boon.
	43	*/
	44
e12a2d53	45	static unsigned long i915_stolen_to_physical(struct drm_device *dev)
9797fbfb CW	46	{
	47	struct drm_i915_private *dev_priv = dev->dev_private;
	48	struct pci_dev *pdev = dev_priv->bridge_dev;
	49	u32 base;
	50
9797fbfb	51	/* On the machines I have tested the Graphics Base of Stolen Memory
e12a2d53 CW	52	* is unreliable, so on those compute the base by subtracting the
	53	* stolen memory from the Top of Low Usable DRAM which is where the
	54	* BIOS places the graphics stolen memory.
	55	*
	56	* On gen2, the layout is slightly different with the Graphics Segment
	57	* immediately following Top of Memory (or Top of Usable DRAM). Note
	58	* it appears that TOUD is only reported by 865g, so we just use the
	59	* top of memory as determined by the e820 probe.
	60	*
	61	* XXX gen2 requires an unavailable symbol and 945gm fails with
	62	* its value of TOLUD.
9797fbfb	63	*/
e12a2d53 CW	64	base = 0;
	65	if (INTEL_INFO(dev)->gen >= 6) {
	66	/* Read Base Data of Stolen Memory Register (BDSM) directly.
	67	* Note that there is also a MCHBAR miror at 0x1080c0 or
	68	* we could use device 2:0x5c instead.
	69	*/
	70	pci_read_config_dword(pdev, 0xB0, &base);
	71	base &= ~4095; /* lower bits used for locking register */
	72	} else if (INTEL_INFO(dev)->gen > 3 \|\| IS_G33(dev)) {
	73	/* Read Graphics Base of Stolen Memory directly */
9797fbfb	74	pci_read_config_dword(pdev, 0xA4, &base);
e12a2d53 CW	75	#if 0
e12a2d53 CW	76	} else if (IS_GEN3(dev)) {
9797fbfb	77	u8 val;
e12a2d53	78	/* Stolen is immediately below Top of Low Usable DRAM */
9797fbfb CW	79	pci_read_config_byte(pdev, 0x9c, &val);
9797fbfb CW	80	base = val >> 3 << 27;
e12a2d53 CW	81	base -= dev_priv->mm.gtt->stolen_size;
	82	} else {
	83	/* Stolen is immediately above Top of Memory */
	84	base = max_low_pfn_mapped << PAGE_SHIFT;
9797fbfb	85	#endif
e12a2d53	86	}
9797fbfb	87
e12a2d53	88	return base;
9797fbfb CW	89	}
9797fbfb CW	90
11be49eb	91	static int i915_setup_compression(struct drm_device *dev, int size)
9797fbfb CW	92	{
	93	struct drm_i915_private *dev_priv = dev->dev_private;
	94	struct drm_mm_node compressed_fb, uninitialized_var(compressed_llb);
9797fbfb	95
11be49eb CW	96	/* Try to over-allocate to reduce reallocations and fragmentation */
	97	compressed_fb = drm_mm_search_free(&dev_priv->mm.stolen,
	98	size <<= 1, 4096, 0);
	99	if (!compressed_fb)
	100	compressed_fb = drm_mm_search_free(&dev_priv->mm.stolen,
	101	size >>= 1, 4096, 0);
9797fbfb CW	102	if (compressed_fb)
	103	compressed_fb = drm_mm_get_block(compressed_fb, size, 4096);
	104	if (!compressed_fb)
	105	goto err;
	106
11be49eb CW	107	if (HAS_PCH_SPLIT(dev))
	108	I915_WRITE(ILK_DPFC_CB_BASE, compressed_fb->start);
	109	else if (IS_GM45(dev)) {
	110	I915_WRITE(DPFC_CB_BASE, compressed_fb->start);
	111	} else {
9797fbfb CW	112	compressed_llb = drm_mm_search_free(&dev_priv->mm.stolen,
	113	4096, 4096, 0);
	114	if (compressed_llb)
	115	compressed_llb = drm_mm_get_block(compressed_llb,
	116	4096, 4096);
	117	if (!compressed_llb)
	118	goto err_fb;
	119
11be49eb CW	120	dev_priv->compressed_llb = compressed_llb;
	121
	122	I915_WRITE(FBC_CFB_BASE,
	123	dev_priv->mm.stolen_base + compressed_fb->start);
	124	I915_WRITE(FBC_LL_BASE,
	125	dev_priv->mm.stolen_base + compressed_llb->start);
9797fbfb CW	126	}
9797fbfb CW	127
11be49eb	128	dev_priv->compressed_fb = compressed_fb;
9797fbfb CW	129	dev_priv->cfb_size = size;
9797fbfb CW	130
11be49eb CW	131	DRM_DEBUG_KMS("reserved %d bytes of contiguous stolen space for FBC\n",
11be49eb CW	132	size);
9797fbfb	133
11be49eb	134	return 0;
9797fbfb	135
9797fbfb CW	136	err_fb:
	137	drm_mm_put_block(compressed_fb);
	138	err:
11be49eb CW	139	return -ENOSPC;
	140	}
	141
	142	int i915_gem_stolen_setup_compression(struct drm_device *dev, int size)
	143	{
	144	struct drm_i915_private *dev_priv = dev->dev_private;
	145
	146	if (dev_priv->mm.stolen_base == 0)
	147	return -ENODEV;
	148
	149	if (size < dev_priv->cfb_size)
	150	return 0;
	151
	152	/* Release any current block */
	153	i915_gem_stolen_cleanup_compression(dev);
	154
	155	return i915_setup_compression(dev, size);
9797fbfb CW	156	}
9797fbfb CW	157
11be49eb	158	void i915_gem_stolen_cleanup_compression(struct drm_device *dev)
9797fbfb CW	159	{
	160	struct drm_i915_private *dev_priv = dev->dev_private;
	161
11be49eb CW	162	if (dev_priv->cfb_size == 0)
	163	return;
	164
	165	if (dev_priv->compressed_fb)
	166	drm_mm_put_block(dev_priv->compressed_fb);
	167
9797fbfb CW	168	if (dev_priv->compressed_llb)
9797fbfb CW	169	drm_mm_put_block(dev_priv->compressed_llb);
11be49eb CW	170
11be49eb CW	171	dev_priv->cfb_size = 0;
9797fbfb CW	172	}
	173
	174	void i915_gem_cleanup_stolen(struct drm_device *dev)
	175	{
4d7bb011 DV	176	struct drm_i915_private *dev_priv = dev->dev_private;
4d7bb011 DV	177
11be49eb	178	i915_gem_stolen_cleanup_compression(dev);
4d7bb011	179	drm_mm_takedown(&dev_priv->mm.stolen);
9797fbfb CW	180	}
	181
	182	int i915_gem_init_stolen(struct drm_device *dev)
	183	{
	184	struct drm_i915_private *dev_priv = dev->dev_private;
9797fbfb	185
e12a2d53 CW	186	dev_priv->mm.stolen_base = i915_stolen_to_physical(dev);
	187	if (dev_priv->mm.stolen_base == 0)
	188	return 0;
	189
a54c0c27 BW	190	DRM_DEBUG_KMS("found %zd bytes of stolen memory at %08lx\n",
a54c0c27 BW	191	dev_priv->gtt.stolen_size, dev_priv->mm.stolen_base);
e12a2d53	192
9797fbfb	193	/* Basic memrange allocator for stolen space */
a54c0c27	194	drm_mm_init(&dev_priv->mm.stolen, 0, dev_priv->gtt.stolen_size);
9797fbfb CW	195
	196	return 0;
	197	}
0104fdbb CW	198
	199	static struct sg_table *
	200	i915_pages_create_for_stolen(struct drm_device *dev,
	201	u32 offset, u32 size)
	202	{
	203	struct drm_i915_private *dev_priv = dev->dev_private;
	204	struct sg_table *st;
	205	struct scatterlist *sg;
	206
	207	DRM_DEBUG_DRIVER("offset=0x%x, size=%d\n", offset, size);
a54c0c27	208	BUG_ON(offset > dev_priv->gtt.stolen_size - size);
0104fdbb CW	209
	210	/* We hide that we have no struct page backing our stolen object
	211	* by wrapping the contiguous physical allocation with a fake
	212	* dma mapping in a single scatterlist.
	213	*/
	214
	215	st = kmalloc(sizeof(*st), GFP_KERNEL);
	216	if (st == NULL)
	217	return NULL;
	218
	219	if (sg_alloc_table(st, 1, GFP_KERNEL)) {
	220	kfree(st);
	221	return NULL;
	222	}
	223
	224	sg = st->sgl;
5bd4687e ID	225	/* we set the dummy page here only to make for_each_sg_page work */
5bd4687e ID	226	sg_set_page(sg, dev_priv->gtt.scratch_page, size, offset);
0104fdbb CW	227
	228	sg_dma_address(sg) = (dma_addr_t)dev_priv->mm.stolen_base + offset;
	229	sg_dma_len(sg) = size;
	230
	231	return st;
	232	}
	233
	234	static int i915_gem_object_get_pages_stolen(struct drm_i915_gem_object *obj)
	235	{
	236	BUG();
	237	return -EINVAL;
	238	}
	239
	240	static void i915_gem_object_put_pages_stolen(struct drm_i915_gem_object *obj)
	241	{
	242	/* Should only be called during free */
	243	sg_free_table(obj->pages);
	244	kfree(obj->pages);
	245	}
	246
	247	static const struct drm_i915_gem_object_ops i915_gem_object_stolen_ops = {
	248	.get_pages = i915_gem_object_get_pages_stolen,
	249	.put_pages = i915_gem_object_put_pages_stolen,
	250	};
	251
	252	static struct drm_i915_gem_object *
	253	_i915_gem_object_create_stolen(struct drm_device *dev,
	254	struct drm_mm_node *stolen)
	255	{
	256	struct drm_i915_gem_object *obj;
	257
42dcedd4	258	obj = i915_gem_object_alloc(dev);
0104fdbb CW	259	if (obj == NULL)
	260	return NULL;
	261
	262	if (drm_gem_private_object_init(dev, &obj->base, stolen->size))
	263	goto cleanup;
	264
	265	i915_gem_object_init(obj, &i915_gem_object_stolen_ops);
	266
	267	obj->pages = i915_pages_create_for_stolen(dev,
	268	stolen->start, stolen->size);
	269	if (obj->pages == NULL)
	270	goto cleanup;
	271
	272	obj->has_dma_mapping = true;
	273	obj->pages_pin_count = 1;
	274	obj->stolen = stolen;
	275
	276	obj->base.write_domain = I915_GEM_DOMAIN_GTT;
	277	obj->base.read_domains = I915_GEM_DOMAIN_GTT;
	278	obj->cache_level = I915_CACHE_NONE;
	279
	280	return obj;
	281
	282	cleanup:
42dcedd4	283	i915_gem_object_free(obj);
0104fdbb CW	284	return NULL;
	285	}
	286
	287	struct drm_i915_gem_object *
	288	i915_gem_object_create_stolen(struct drm_device *dev, u32 size)
	289	{
	290	struct drm_i915_private *dev_priv = dev->dev_private;
	291	struct drm_i915_gem_object *obj;
	292	struct drm_mm_node *stolen;
	293
	294	if (dev_priv->mm.stolen_base == 0)
	295	return NULL;
	296
	297	DRM_DEBUG_KMS("creating stolen object: size=%x\n", size);
	298	if (size == 0)
	299	return NULL;
	300
	301	stolen = drm_mm_search_free(&dev_priv->mm.stolen, size, 4096, 0);
	302	if (stolen)
	303	stolen = drm_mm_get_block(stolen, size, 4096);
	304	if (stolen == NULL)
	305	return NULL;
	306
	307	obj = _i915_gem_object_create_stolen(dev, stolen);
	308	if (obj)
	309	return obj;
	310
	311	drm_mm_put_block(stolen);
	312	return NULL;
	313	}
	314
	315	void
	316	i915_gem_object_release_stolen(struct drm_i915_gem_object *obj)
	317	{
	318	if (obj->stolen) {
	319	drm_mm_put_block(obj->stolen);
	320	obj->stolen = NULL;
	321	}
	322	}