drivers/gpu/drm/i915/i915_gem_tiling.c - kernel/msm-4.9 - Gitiles

 /*
  * Copyright © 2008 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>
  *
  */

 #include "drmP.h"
 #include "drm.h"
 #include "i915_drm.h"
 #include "i915_drv.h"

 /** @file i915_gem_tiling.c
  *
  * Support for managing tiling state of buffer objects.
  *
  * The idea behind tiling is to increase cache hit rates by rearranging
  * pixel data so that a group of pixel accesses are in the same cacheline.
  * Performance improvement from doing this on the back/depth buffer are on
  * the order of 30%.
  *
  * Intel architectures make this somewhat more complicated, though, by
  * adjustments made to addressing of data when the memory is in interleaved
  * mode (matched pairs of DIMMS) to improve memory bandwidth.
  * For interleaved memory, the CPU sends every sequential 64 bytes
  * to an alternate memory channel so it can get the bandwidth from both.
  *
  * The GPU also rearranges its accesses for increased bandwidth to interleaved
  * memory, and it matches what the CPU does for non-tiled.  However, when tiled
  * it does it a little differently, since one walks addresses not just in the
  * X direction but also Y.  So, along with alternating channels when bit
  * 6 of the address flips, it also alternates when other bits flip --  Bits 9
  * (every 512 bytes, an X tile scanline) and 10 (every two X tile scanlines)
  * are common to both the 915 and 965-class hardware.
  *
  * The CPU also sometimes XORs in higher bits as well, to improve
  * bandwidth doing strided access like we do so frequently in graphics.  This
  * is called "Channel XOR Randomization" in the MCH documentation.  The result
  * is that the CPU is XORing in either bit 11 or bit 17 to bit 6 of its address
  * decode.
  *
  * All of this bit 6 XORing has an effect on our memory management,
  * as we need to make sure that the 3d driver can correctly address object
  * contents.
  *
  * If we don't have interleaved memory, all tiling is safe and no swizzling is
  * required.
  *
  * When bit 17 is XORed in, we simply refuse to tile at all.  Bit
  * 17 is not just a page offset, so as we page an objet out and back in,
  * individual pages in it will have different bit 17 addresses, resulting in
  * each 64 bytes being swapped with its neighbor!
  *
  * Otherwise, if interleaved, we have to tell the 3d driver what the address
  * swizzling it needs to do is, since it's writing with the CPU to the pages
  * (bit 6 and potentially bit 11 XORed in), and the GPU is reading from the
  * pages (bit 6, 9, and 10 XORed in), resulting in a cumulative bit swizzling
  * required by the CPU of XORing in bit 6, 9, 10, and potentially 11, in order
  * to match what the GPU expects.
  */

 /**
  * Detects bit 6 swizzling of address lookup between IGD access and CPU
  * access through main memory.
  */
 void
 i915_gem_detect_bit_6_swizzle(struct drm_device *dev)
 {
 	drm_i915_private_t *dev_priv = dev->dev_private;
 	uint32_t swizzle_x = I915_BIT_6_SWIZZLE_UNKNOWN;
 	uint32_t swizzle_y = I915_BIT_6_SWIZZLE_UNKNOWN;

 	if (!IS_I9XX(dev)) {
 		/* As far as we know, the 865 doesn't have these bit 6
 		 * swizzling issues.
 		 */
 		swizzle_x = I915_BIT_6_SWIZZLE_NONE;
 		swizzle_y = I915_BIT_6_SWIZZLE_NONE;
 	} else if ((!IS_I965G(dev) && !IS_G33(dev)) || IS_I965GM(dev) ||
 		   IS_GM45(dev)) {
 		uint32_t dcc;

 		/* On 915-945 and GM965, channel interleave by the CPU is
 		 * determined by DCC.  The CPU will alternate based on bit 6
 		 * in interleaved mode, and the GPU will then also alternate
 		 * on bit 6, 9, and 10 for X, but the CPU may also optionally
 		 * alternate based on bit 17 (XOR not disabled and XOR
 		 * bit == 17).
 		 */
 		dcc = I915_READ(DCC);
 		switch (dcc & DCC_ADDRESSING_MODE_MASK) {
 		case DCC_ADDRESSING_MODE_SINGLE_CHANNEL:
 		case DCC_ADDRESSING_MODE_DUAL_CHANNEL_ASYMMETRIC:
 			swizzle_x = I915_BIT_6_SWIZZLE_NONE;
 			swizzle_y = I915_BIT_6_SWIZZLE_NONE;
 			break;
 		case DCC_ADDRESSING_MODE_DUAL_CHANNEL_INTERLEAVED:
 			if (IS_I915G(dev) || IS_I915GM(dev) ||
 			    dcc & DCC_CHANNEL_XOR_DISABLE) {
 				swizzle_x = I915_BIT_6_SWIZZLE_9_10;
 				swizzle_y = I915_BIT_6_SWIZZLE_9;
 			} else if ((IS_I965GM(dev) || IS_GM45(dev)) &&
 				   (dcc & DCC_CHANNEL_XOR_BIT_17) == 0) {
 				/* GM965/GM45 does either bit 11 or bit 17
 				 * swizzling.
 				 */
 				swizzle_x = I915_BIT_6_SWIZZLE_9_10_11;
 				swizzle_y = I915_BIT_6_SWIZZLE_9_11;
 			} else {
 				/* Bit 17 or perhaps other swizzling */
 				swizzle_x = I915_BIT_6_SWIZZLE_UNKNOWN;
 				swizzle_y = I915_BIT_6_SWIZZLE_UNKNOWN;
 			}
 			break;
 		}
 		if (dcc == 0xffffffff) {
 			DRM_ERROR("Couldn't read from MCHBAR.  "
 				  "Disabling tiling.\n");
 			swizzle_x = I915_BIT_6_SWIZZLE_UNKNOWN;
 			swizzle_y = I915_BIT_6_SWIZZLE_UNKNOWN;
 		}
 	} else {
 		/* The 965, G33, and newer, have a very flexible memory
 		 * configuration.  It will enable dual-channel mode
 		 * (interleaving) on as much memory as it can, and the GPU
 		 * will additionally sometimes enable different bit 6
 		 * swizzling for tiled objects from the CPU.
 		 *
 		 * Here's what I found on the G965:
 		 *    slot fill         memory size  swizzling
 		 * 0A   0B   1A   1B    1-ch   2-ch
 		 * 512  0    0    0     512    0     O
 		 * 512  0    512  0     16     1008  X
 		 * 512  0    0    512   16     1008  X
 		 * 0    512  0    512   16     1008  X
 		 * 1024 1024 1024 0     2048   1024  O
 		 *
 		 * We could probably detect this based on either the DRB
 		 * matching, which was the case for the swizzling required in
 		 * the table above, or from the 1-ch value being less than
 		 * the minimum size of a rank.
 		 */
 		if (I915_READ16(C0DRB3) != I915_READ16(C1DRB3)) {
 			swizzle_x = I915_BIT_6_SWIZZLE_NONE;
 			swizzle_y = I915_BIT_6_SWIZZLE_NONE;
 		} else {
 			swizzle_x = I915_BIT_6_SWIZZLE_9_10;
 			swizzle_y = I915_BIT_6_SWIZZLE_9;
 		}
 	}

 	dev_priv->mm.bit_6_swizzle_x = swizzle_x;
 	dev_priv->mm.bit_6_swizzle_y = swizzle_y;
 }


 /**
  * Returns the size of the fence for a tiled object of the given size.
  */
 static int
 i915_get_fence_size(struct drm_device *dev, int size)
 {
 	int i;
 	int start;

 	if (IS_I965G(dev)) {
 		/* The 965 can have fences at any page boundary. */
 		return ALIGN(size, 4096);
 	} else {
 		/* Align the size to a power of two greater than the smallest
 		 * fence size.
 		 */
 		if (IS_I9XX(dev))
 			start = 1024 * 1024;
 		else
 			start = 512 * 1024;

 		for (i = start; i < size; i <<= 1)
 			;

 		return i;
 	}
 }

 /* Check pitch constriants for all chips & tiling formats */
 static bool
 i915_tiling_ok(struct drm_device *dev, int stride, int size, int tiling_mode)
 {
 	int tile_width;

 	/* Linear is always fine */
 	if (tiling_mode == I915_TILING_NONE)
 		return true;

 	if (tiling_mode == I915_TILING_Y && HAS_128_BYTE_Y_TILING(dev))
 		tile_width = 128;
 	else
 		tile_width = 512;

 	/* 965+ just needs multiples of tile width */
 	if (IS_I965G(dev)) {
 		if (stride & (tile_width - 1))
 			return false;
 		return true;
 	}

 	/* Pre-965 needs power of two tile widths */
 	if (stride < tile_width)
 		return false;

 	if (stride & (stride - 1))
 		return false;

 	/* We don't handle the aperture area covered by the fence being bigger
 	 * than the object size.
 	 */
 	if (i915_get_fence_size(dev, size) != size)
 		return false;

 	return true;
 }

 /**
  * Sets the tiling mode of an object, returning the required swizzling of
  * bit 6 of addresses in the object.
  */
 int
 i915_gem_set_tiling(struct drm_device *dev, void *data,
 		   struct drm_file *file_priv)
 {
 	struct drm_i915_gem_set_tiling *args = data;
 	drm_i915_private_t *dev_priv = dev->dev_private;
 	struct drm_gem_object *obj;
 	struct drm_i915_gem_object *obj_priv;

 	obj = drm_gem_object_lookup(dev, file_priv, args->handle);
 	if (obj == NULL)
 		return -EINVAL;
 	obj_priv = obj->driver_private;

 	if (!i915_tiling_ok(dev, args->stride, obj->size, args->tiling_mode)) {
 		drm_gem_object_unreference(obj);
 		return -EINVAL;
 	}

 	mutex_lock(&dev->struct_mutex);

 	if (args->tiling_mode == I915_TILING_NONE) {
 		obj_priv->tiling_mode = I915_TILING_NONE;
 		args->swizzle_mode = I915_BIT_6_SWIZZLE_NONE;
 	} else {
 		if (args->tiling_mode == I915_TILING_X)
 			args->swizzle_mode = dev_priv->mm.bit_6_swizzle_x;
 		else
 			args->swizzle_mode = dev_priv->mm.bit_6_swizzle_y;
 		/* If we can't handle the swizzling, make it untiled. */
 		if (args->swizzle_mode == I915_BIT_6_SWIZZLE_UNKNOWN) {
 			args->tiling_mode = I915_TILING_NONE;
 			args->swizzle_mode = I915_BIT_6_SWIZZLE_NONE;
 		}
 	}
 	if (args->tiling_mode != obj_priv->tiling_mode) {
 		int ret;

 		/* Unbind the object, as switching tiling means we're
 		 * switching the cache organization due to fencing, probably.
 		 */
 		ret = i915_gem_object_unbind(obj);
 		if (ret != 0) {
 			WARN(ret != -ERESTARTSYS,
 			     "failed to unbind object for tiling switch");
 			args->tiling_mode = obj_priv->tiling_mode;
 			mutex_unlock(&dev->struct_mutex);
 			drm_gem_object_unreference(obj);

 			return ret;
 		}
 		obj_priv->tiling_mode = args->tiling_mode;
 	}
 	obj_priv->stride = args->stride;

 	mutex_unlock(&dev->struct_mutex);

 	drm_gem_object_unreference(obj);

 	return 0;
 }

 /**
  * Returns the current tiling mode and required bit 6 swizzling for the object.
  */
 int
 i915_gem_get_tiling(struct drm_device *dev, void *data,
 		   struct drm_file *file_priv)
 {
 	struct drm_i915_gem_get_tiling *args = data;
 	drm_i915_private_t *dev_priv = dev->dev_private;
 	struct drm_gem_object *obj;
 	struct drm_i915_gem_object *obj_priv;

 	obj = drm_gem_object_lookup(dev, file_priv, args->handle);
 	if (obj == NULL)
 		return -EINVAL;
 	obj_priv = obj->driver_private;

 	mutex_lock(&dev->struct_mutex);

 	args->tiling_mode = obj_priv->tiling_mode;
 	switch (obj_priv->tiling_mode) {
 	case I915_TILING_X:
 		args->swizzle_mode = dev_priv->mm.bit_6_swizzle_x;
 		break;
 	case I915_TILING_Y:
 		args->swizzle_mode = dev_priv->mm.bit_6_swizzle_y;
 		break;
 	case I915_TILING_NONE:
 		args->swizzle_mode = I915_BIT_6_SWIZZLE_NONE;
 		break;
 	default:
 		DRM_ERROR("unknown tiling mode\n");
 	}

 	mutex_unlock(&dev->struct_mutex);

 	drm_gem_object_unreference(obj);

 	return 0;
 }
	/*
	* Copyright © 2008 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>
	*
	*/

	#include "drmP.h"
	#include "drm.h"
	#include "i915_drm.h"
	#include "i915_drv.h"

	/** @file i915_gem_tiling.c
	*
	* Support for managing tiling state of buffer objects.
	*
	* The idea behind tiling is to increase cache hit rates by rearranging
	* pixel data so that a group of pixel accesses are in the same cacheline.
	* Performance improvement from doing this on the back/depth buffer are on
	* the order of 30%.
	*
	* Intel architectures make this somewhat more complicated, though, by
	* adjustments made to addressing of data when the memory is in interleaved
	* mode (matched pairs of DIMMS) to improve memory bandwidth.
	* For interleaved memory, the CPU sends every sequential 64 bytes
	* to an alternate memory channel so it can get the bandwidth from both.
	*
	* The GPU also rearranges its accesses for increased bandwidth to interleaved
	* memory, and it matches what the CPU does for non-tiled. However, when tiled
	* it does it a little differently, since one walks addresses not just in the
	* X direction but also Y. So, along with alternating channels when bit
	* 6 of the address flips, it also alternates when other bits flip -- Bits 9
	* (every 512 bytes, an X tile scanline) and 10 (every two X tile scanlines)
	* are common to both the 915 and 965-class hardware.
	*
	* The CPU also sometimes XORs in higher bits as well, to improve
	* bandwidth doing strided access like we do so frequently in graphics. This
	* is called "Channel XOR Randomization" in the MCH documentation. The result
	* is that the CPU is XORing in either bit 11 or bit 17 to bit 6 of its address
	* decode.
	*
	* All of this bit 6 XORing has an effect on our memory management,
	* as we need to make sure that the 3d driver can correctly address object
	* contents.
	*
	* If we don't have interleaved memory, all tiling is safe and no swizzling is
	* required.
	*
	* When bit 17 is XORed in, we simply refuse to tile at all. Bit
	* 17 is not just a page offset, so as we page an objet out and back in,
	* individual pages in it will have different bit 17 addresses, resulting in
	* each 64 bytes being swapped with its neighbor!
	*
	* Otherwise, if interleaved, we have to tell the 3d driver what the address
	* swizzling it needs to do is, since it's writing with the CPU to the pages
	* (bit 6 and potentially bit 11 XORed in), and the GPU is reading from the
	* pages (bit 6, 9, and 10 XORed in), resulting in a cumulative bit swizzling
	* required by the CPU of XORing in bit 6, 9, 10, and potentially 11, in order
	* to match what the GPU expects.
	*/

	/**
	* Detects bit 6 swizzling of address lookup between IGD access and CPU
	* access through main memory.
	*/
	void
	i915_gem_detect_bit_6_swizzle(struct drm_device *dev)
	{
	drm_i915_private_t *dev_priv = dev->dev_private;
	uint32_t swizzle_x = I915_BIT_6_SWIZZLE_UNKNOWN;
	uint32_t swizzle_y = I915_BIT_6_SWIZZLE_UNKNOWN;

	if (!IS_I9XX(dev)) {
	/* As far as we know, the 865 doesn't have these bit 6
	* swizzling issues.
	*/
	swizzle_x = I915_BIT_6_SWIZZLE_NONE;
	swizzle_y = I915_BIT_6_SWIZZLE_NONE;
	} else if ((!IS_I965G(dev) && !IS_G33(dev)) \|\| IS_I965GM(dev) \|\|
	IS_GM45(dev)) {
	uint32_t dcc;

	/* On 915-945 and GM965, channel interleave by the CPU is
	* determined by DCC. The CPU will alternate based on bit 6
	* in interleaved mode, and the GPU will then also alternate
	* on bit 6, 9, and 10 for X, but the CPU may also optionally
	* alternate based on bit 17 (XOR not disabled and XOR
	* bit == 17).
	*/
	dcc = I915_READ(DCC);
	switch (dcc & DCC_ADDRESSING_MODE_MASK) {
	case DCC_ADDRESSING_MODE_SINGLE_CHANNEL:
	case DCC_ADDRESSING_MODE_DUAL_CHANNEL_ASYMMETRIC:
	swizzle_x = I915_BIT_6_SWIZZLE_NONE;
	swizzle_y = I915_BIT_6_SWIZZLE_NONE;
	break;
	case DCC_ADDRESSING_MODE_DUAL_CHANNEL_INTERLEAVED:
	if (IS_I915G(dev) \|\| IS_I915GM(dev) \|\|
	dcc & DCC_CHANNEL_XOR_DISABLE) {
	swizzle_x = I915_BIT_6_SWIZZLE_9_10;
	swizzle_y = I915_BIT_6_SWIZZLE_9;
	} else if ((IS_I965GM(dev) \|\| IS_GM45(dev)) &&
	(dcc & DCC_CHANNEL_XOR_BIT_17) == 0) {
	/* GM965/GM45 does either bit 11 or bit 17
	* swizzling.
	*/
	swizzle_x = I915_BIT_6_SWIZZLE_9_10_11;
	swizzle_y = I915_BIT_6_SWIZZLE_9_11;
	} else {
	/* Bit 17 or perhaps other swizzling */
	swizzle_x = I915_BIT_6_SWIZZLE_UNKNOWN;
	swizzle_y = I915_BIT_6_SWIZZLE_UNKNOWN;
	}
	break;
	}
	if (dcc == 0xffffffff) {
	DRM_ERROR("Couldn't read from MCHBAR. "
	"Disabling tiling.\n");
	swizzle_x = I915_BIT_6_SWIZZLE_UNKNOWN;
	swizzle_y = I915_BIT_6_SWIZZLE_UNKNOWN;
	}
	} else {
	/* The 965, G33, and newer, have a very flexible memory
	* configuration. It will enable dual-channel mode
	* (interleaving) on as much memory as it can, and the GPU
	* will additionally sometimes enable different bit 6
	* swizzling for tiled objects from the CPU.
	*
	* Here's what I found on the G965:
	* slot fill memory size swizzling
	* 0A 0B 1A 1B 1-ch 2-ch
	* 512 0 0 0 512 0 O
	* 512 0 512 0 16 1008 X
	* 512 0 0 512 16 1008 X
	* 0 512 0 512 16 1008 X
	* 1024 1024 1024 0 2048 1024 O
	*
	* We could probably detect this based on either the DRB
	* matching, which was the case for the swizzling required in
	* the table above, or from the 1-ch value being less than
	* the minimum size of a rank.
	*/
	if (I915_READ16(C0DRB3) != I915_READ16(C1DRB3)) {
	swizzle_x = I915_BIT_6_SWIZZLE_NONE;
	swizzle_y = I915_BIT_6_SWIZZLE_NONE;
	} else {
	swizzle_x = I915_BIT_6_SWIZZLE_9_10;
	swizzle_y = I915_BIT_6_SWIZZLE_9;
	}
	}

	dev_priv->mm.bit_6_swizzle_x = swizzle_x;
	dev_priv->mm.bit_6_swizzle_y = swizzle_y;
	}


	/**
	* Returns the size of the fence for a tiled object of the given size.
	*/
	static int
	i915_get_fence_size(struct drm_device *dev, int size)
	{
	int i;
	int start;

	if (IS_I965G(dev)) {
	/* The 965 can have fences at any page boundary. */
	return ALIGN(size, 4096);
	} else {
	/* Align the size to a power of two greater than the smallest
	* fence size.
	*/
	if (IS_I9XX(dev))
	start = 1024 * 1024;
	else
	start = 512 * 1024;

	for (i = start; i < size; i <<= 1)
	;

	return i;
	}
	}

	/* Check pitch constriants for all chips & tiling formats */
	static bool
	i915_tiling_ok(struct drm_device *dev, int stride, int size, int tiling_mode)
	{
	int tile_width;

	/* Linear is always fine */
	if (tiling_mode == I915_TILING_NONE)
	return true;

	if (tiling_mode == I915_TILING_Y && HAS_128_BYTE_Y_TILING(dev))
	tile_width = 128;
	else
	tile_width = 512;

	/* 965+ just needs multiples of tile width */
	if (IS_I965G(dev)) {
	if (stride & (tile_width - 1))
	return false;
	return true;
	}

	/* Pre-965 needs power of two tile widths */
	if (stride < tile_width)
	return false;

	if (stride & (stride - 1))
	return false;

	/* We don't handle the aperture area covered by the fence being bigger
	* than the object size.
	*/
	if (i915_get_fence_size(dev, size) != size)
	return false;

	return true;
	}

	/**
	* Sets the tiling mode of an object, returning the required swizzling of
	* bit 6 of addresses in the object.
	*/
	int
	i915_gem_set_tiling(struct drm_device dev, void data,
	struct drm_file *file_priv)
	{
	struct drm_i915_gem_set_tiling *args = data;
	drm_i915_private_t *dev_priv = dev->dev_private;
	struct drm_gem_object *obj;
	struct drm_i915_gem_object *obj_priv;

	obj = drm_gem_object_lookup(dev, file_priv, args->handle);
	if (obj == NULL)
	return -EINVAL;
	obj_priv = obj->driver_private;

	if (!i915_tiling_ok(dev, args->stride, obj->size, args->tiling_mode)) {
	drm_gem_object_unreference(obj);
	return -EINVAL;
	}

	mutex_lock(&dev->struct_mutex);

	if (args->tiling_mode == I915_TILING_NONE) {
	obj_priv->tiling_mode = I915_TILING_NONE;
	args->swizzle_mode = I915_BIT_6_SWIZZLE_NONE;
	} else {
	if (args->tiling_mode == I915_TILING_X)
	args->swizzle_mode = dev_priv->mm.bit_6_swizzle_x;
	else
	args->swizzle_mode = dev_priv->mm.bit_6_swizzle_y;
	/* If we can't handle the swizzling, make it untiled. */
	if (args->swizzle_mode == I915_BIT_6_SWIZZLE_UNKNOWN) {
	args->tiling_mode = I915_TILING_NONE;
	args->swizzle_mode = I915_BIT_6_SWIZZLE_NONE;
	}
	}
	if (args->tiling_mode != obj_priv->tiling_mode) {
	int ret;

	/* Unbind the object, as switching tiling means we're
	* switching the cache organization due to fencing, probably.
	*/
	ret = i915_gem_object_unbind(obj);
	if (ret != 0) {
	WARN(ret != -ERESTARTSYS,
	"failed to unbind object for tiling switch");
	args->tiling_mode = obj_priv->tiling_mode;
	mutex_unlock(&dev->struct_mutex);
	drm_gem_object_unreference(obj);

	return ret;
	}
	obj_priv->tiling_mode = args->tiling_mode;
	}
	obj_priv->stride = args->stride;

	mutex_unlock(&dev->struct_mutex);

	drm_gem_object_unreference(obj);

	return 0;
	}

	/**
	* Returns the current tiling mode and required bit 6 swizzling for the object.
	*/
	int
	i915_gem_get_tiling(struct drm_device dev, void data,
	struct drm_file *file_priv)
	{
	struct drm_i915_gem_get_tiling *args = data;
	drm_i915_private_t *dev_priv = dev->dev_private;
	struct drm_gem_object *obj;
	struct drm_i915_gem_object *obj_priv;

	obj = drm_gem_object_lookup(dev, file_priv, args->handle);
	if (obj == NULL)
	return -EINVAL;
	obj_priv = obj->driver_private;

	mutex_lock(&dev->struct_mutex);

	args->tiling_mode = obj_priv->tiling_mode;
	switch (obj_priv->tiling_mode) {
	case I915_TILING_X:
	args->swizzle_mode = dev_priv->mm.bit_6_swizzle_x;
	break;
	case I915_TILING_Y:
	args->swizzle_mode = dev_priv->mm.bit_6_swizzle_y;
	break;
	case I915_TILING_NONE:
	args->swizzle_mode = I915_BIT_6_SWIZZLE_NONE;
	break;
	default:
	DRM_ERROR("unknown tiling mode\n");
	}

	mutex_unlock(&dev->struct_mutex);

	drm_gem_object_unreference(obj);

	return 0;
	}