drivers/gpu/drm/i915/i915_gem_tiling.c - linux - Git at Google

 /*
  * 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 <linux/string.h>
 #include <linux/bitops.h>
 #include <drm/drmP.h>
 #include <drm/i915_drm.h>
 #include "i915_drv.h"

 /**
  * DOC: buffer object tiling
  *
  * i915_gem_set_tiling_ioctl() and i915_gem_get_tiling_ioctl() is the userspace
  * interface to declare fence register requirements.
  *
  * In principle GEM doesn't care at all about the internal data layout of an
  * object, and hence it also doesn't care about tiling or swizzling. There's two
  * exceptions:
  *
  * - For X and Y tiling the hardware provides detilers for CPU access, so called
  *   fences. Since there's only a limited amount of them the kernel must manage
  *   these, and therefore userspace must tell the kernel the object tiling if it
  *   wants to use fences for detiling.
  * - On gen3 and gen4 platforms have a swizzling pattern for tiled objects which
  *   depends upon the physical page frame number. When swapping such objects the
  *   page frame number might change and the kernel must be able to fix this up
  *   and hence now the tiling. Note that on a subset of platforms with
  *   asymmetric memory channel population the swizzling pattern changes in an
  *   unknown way, and for those the kernel simply forbids swapping completely.
  *
  * Since neither of this applies for new tiling layouts on modern platforms like
  * W, Ys and Yf tiling GEM only allows object tiling to be set to X or Y tiled.
  * Anything else can be handled in userspace entirely without the kernel's
  * invovlement.
  */

 /**
  * i915_gem_fence_size - required global GTT size for a fence
  * @i915: i915 device
  * @size: object size
  * @tiling: tiling mode
  * @stride: tiling stride
  *
  * Return the required global GTT size for a fence (view of a tiled object),
  * taking into account potential fence register mapping.
  */
 u32 i915_gem_fence_size(struct drm_i915_private *i915,
 			u32 size, unsigned int tiling, unsigned int stride)
 {
 	u32 ggtt_size;

 	GEM_BUG_ON(!size);

 	if (tiling == I915_TILING_NONE)
 		return size;

 	GEM_BUG_ON(!stride);

 	if (INTEL_GEN(i915) >= 4) {
 		stride *= i915_gem_tile_height(tiling);
 		GEM_BUG_ON(!IS_ALIGNED(stride, I965_FENCE_PAGE));
 		return roundup(size, stride);
 	}

 	/* Previous chips need a power-of-two fence region when tiling */
 	if (IS_GEN3(i915))
 		ggtt_size = 1024*1024;
 	else
 		ggtt_size = 512*1024;

 	while (ggtt_size < size)
 		ggtt_size <<= 1;

 	return ggtt_size;
 }

 /**
  * i915_gem_fence_alignment - required global GTT alignment for a fence
  * @i915: i915 device
  * @size: object size
  * @tiling: tiling mode
  * @stride: tiling stride
  *
  * Return the required global GTT alignment for a fence (a view of a tiled
  * object), taking into account potential fence register mapping.
  */
 u32 i915_gem_fence_alignment(struct drm_i915_private *i915, u32 size,
 			     unsigned int tiling, unsigned int stride)
 {
 	GEM_BUG_ON(!size);

 	/*
 	 * Minimum alignment is 4k (GTT page size), but might be greater
 	 * if a fence register is needed for the object.
 	 */
 	if (tiling == I915_TILING_NONE)
 		return I915_GTT_MIN_ALIGNMENT;

 	if (INTEL_GEN(i915) >= 4)
 		return I965_FENCE_PAGE;

 	/*
 	 * Previous chips need to be aligned to the size of the smallest
 	 * fence register that can contain the object.
 	 */
 	return i915_gem_fence_size(i915, size, tiling, stride);
 }

 /* Check pitch constriants for all chips & tiling formats */
 static bool
 i915_tiling_ok(struct drm_i915_gem_object *obj,
 	       unsigned int tiling, unsigned int stride)
 {
 	struct drm_i915_private *i915 = to_i915(obj->base.dev);
 	unsigned int tile_width;

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

 	if (tiling > I915_TILING_LAST)
 		return false;

 	/* check maximum stride & object size */
 	/* i965+ stores the end address of the gtt mapping in the fence
 	 * reg, so dont bother to check the size */
 	if (INTEL_GEN(i915) >= 7) {
 		if (stride / 128 > GEN7_FENCE_MAX_PITCH_VAL)
 			return false;
 	} else if (INTEL_GEN(i915) >= 4) {
 		if (stride / 128 > I965_FENCE_MAX_PITCH_VAL)
 			return false;
 	} else {
 		if (stride > 8192)
 			return false;

 		if (!is_power_of_2(stride))
 			return false;
 	}

 	if (IS_GEN2(i915) ||
 	    (tiling == I915_TILING_Y && HAS_128_BYTE_Y_TILING(i915)))
 		tile_width = 128;
 	else
 		tile_width = 512;

 	if (!stride || !IS_ALIGNED(stride, tile_width))
 		return false;

 	return true;
 }

 static bool i915_vma_fence_prepare(struct i915_vma *vma,
 				   int tiling_mode, unsigned int stride)
 {
 	struct drm_i915_private *i915 = vma->vm->i915;
 	u32 size, alignment;

 	if (!i915_vma_is_map_and_fenceable(vma))
 		return true;

 	size = i915_gem_fence_size(i915, vma->size, tiling_mode, stride);
 	if (vma->node.size < size)
 		return false;

 	alignment = i915_gem_fence_alignment(i915, vma->size, tiling_mode, stride);
 	if (!IS_ALIGNED(vma->node.start, alignment))
 		return false;

 	return true;
 }

 /* Make the current GTT allocation valid for the change in tiling. */
 static int
 i915_gem_object_fence_prepare(struct drm_i915_gem_object *obj,
 			      int tiling_mode, unsigned int stride)
 {
 	struct i915_vma *vma;
 	int ret;

 	if (tiling_mode == I915_TILING_NONE)
 		return 0;

 	for_each_ggtt_vma(vma, obj) {
 		if (i915_vma_fence_prepare(vma, tiling_mode, stride))
 			continue;

 		ret = i915_vma_unbind(vma);
 		if (ret)
 			return ret;
 	}

 	return 0;
 }

 int
 i915_gem_object_set_tiling(struct drm_i915_gem_object *obj,
 			   unsigned int tiling, unsigned int stride)
 {
 	struct drm_i915_private *i915 = to_i915(obj->base.dev);
 	struct i915_vma *vma;
 	int err;

 	/* Make sure we don't cross-contaminate obj->tiling_and_stride */
 	BUILD_BUG_ON(I915_TILING_LAST & STRIDE_MASK);

 	GEM_BUG_ON(!i915_tiling_ok(obj, tiling, stride));
 	GEM_BUG_ON(!stride ^ (tiling == I915_TILING_NONE));
 	lockdep_assert_held(&i915->drm.struct_mutex);

 	if ((tiling | stride) == obj->tiling_and_stride)
 		return 0;

 	if (i915_gem_object_is_framebuffer(obj))
 		return -EBUSY;

 	/* We need to rebind the object if its current allocation
 	 * no longer meets the alignment restrictions for its new
 	 * tiling mode. Otherwise we can just leave it alone, but
 	 * need to ensure that any fence register is updated before
 	 * the next fenced (either through the GTT or by the BLT unit
 	 * on older GPUs) access.
 	 *
 	 * After updating the tiling parameters, we then flag whether
 	 * we need to update an associated fence register. Note this
 	 * has to also include the unfenced register the GPU uses
 	 * whilst executing a fenced command for an untiled object.
 	 */

 	err = i915_gem_object_fence_prepare(obj, tiling, stride);
 	if (err)
 		return err;

 	i915_gem_object_lock(obj);
 	if (i915_gem_object_is_framebuffer(obj)) {
 		i915_gem_object_unlock(obj);
 		return -EBUSY;
 	}

 	/* If the memory has unknown (i.e. varying) swizzling, we pin the
 	 * pages to prevent them being swapped out and causing corruption
 	 * due to the change in swizzling.
 	 */
 	mutex_lock(&obj->mm.lock);
 	if (i915_gem_object_has_pages(obj) &&
 	    obj->mm.madv == I915_MADV_WILLNEED &&
 	    i915->quirks & QUIRK_PIN_SWIZZLED_PAGES) {
 		if (tiling == I915_TILING_NONE) {
 			GEM_BUG_ON(!obj->mm.quirked);
 			__i915_gem_object_unpin_pages(obj);
 			obj->mm.quirked = false;
 		}
 		if (!i915_gem_object_is_tiled(obj)) {
 			GEM_BUG_ON(obj->mm.quirked);
 			__i915_gem_object_pin_pages(obj);
 			obj->mm.quirked = true;
 		}
 	}
 	mutex_unlock(&obj->mm.lock);

 	for_each_ggtt_vma(vma, obj) {
 		vma->fence_size =
 			i915_gem_fence_size(i915, vma->size, tiling, stride);
 		vma->fence_alignment =
 			i915_gem_fence_alignment(i915,
 						 vma->size, tiling, stride);

 		if (vma->fence)
 			vma->fence->dirty = true;
 	}

 	obj->tiling_and_stride = tiling | stride;
 	i915_gem_object_unlock(obj);

 	/* Force the fence to be reacquired for GTT access */
 	i915_gem_release_mmap(obj);

 	/* Try to preallocate memory required to save swizzling on put-pages */
 	if (i915_gem_object_needs_bit17_swizzle(obj)) {
 		if (!obj->bit_17) {
 			obj->bit_17 = kcalloc(BITS_TO_LONGS(obj->base.size >> PAGE_SHIFT),
 					      sizeof(long), GFP_KERNEL);
 		}
 	} else {
 		kfree(obj->bit_17);
 		obj->bit_17 = NULL;
 	}

 	return 0;
 }

 /**
  * i915_gem_set_tiling_ioctl - IOCTL handler to set tiling mode
  * @dev: DRM device
  * @data: data pointer for the ioctl
  * @file: DRM file for the ioctl call
  *
  * Sets the tiling mode of an object, returning the required swizzling of
  * bit 6 of addresses in the object.
  *
  * Called by the user via ioctl.
  *
  * Returns:
  * Zero on success, negative errno on failure.
  */
 int
 i915_gem_set_tiling_ioctl(struct drm_device *dev, void *data,
 			  struct drm_file *file)
 {
 	struct drm_i915_gem_set_tiling *args = data;
 	struct drm_i915_gem_object *obj;
 	int err;

 	obj = i915_gem_object_lookup(file, args->handle);
 	if (!obj)
 		return -ENOENT;

 	/*
 	 * The tiling mode of proxy objects is handled by its generator, and
 	 * not allowed to be changed by userspace.
 	 */
 	if (i915_gem_object_is_proxy(obj)) {
 		err = -ENXIO;
 		goto err;
 	}

 	if (!i915_tiling_ok(obj, args->tiling_mode, args->stride)) {
 		err = -EINVAL;
 		goto err;
 	}

 	if (args->tiling_mode == I915_TILING_NONE) {
 		args->swizzle_mode = I915_BIT_6_SWIZZLE_NONE;
 		args->stride = 0;
 	} else {
 		if (args->tiling_mode == I915_TILING_X)
 			args->swizzle_mode = to_i915(dev)->mm.bit_6_swizzle_x;
 		else
 			args->swizzle_mode = to_i915(dev)->mm.bit_6_swizzle_y;

 		/* Hide bit 17 swizzling from the user.  This prevents old Mesa
 		 * from aborting the application on sw fallbacks to bit 17,
 		 * and we use the pread/pwrite bit17 paths to swizzle for it.
 		 * If there was a user that was relying on the swizzle
 		 * information for drm_intel_bo_map()ed reads/writes this would
 		 * break it, but we don't have any of those.
 		 */
 		if (args->swizzle_mode == I915_BIT_6_SWIZZLE_9_17)
 			args->swizzle_mode = I915_BIT_6_SWIZZLE_9;
 		if (args->swizzle_mode == I915_BIT_6_SWIZZLE_9_10_17)
 			args->swizzle_mode = I915_BIT_6_SWIZZLE_9_10;

 		/* 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;
 			args->stride = 0;
 		}
 	}

 	err = mutex_lock_interruptible(&dev->struct_mutex);
 	if (err)
 		goto err;

 	err = i915_gem_object_set_tiling(obj, args->tiling_mode, args->stride);
 	mutex_unlock(&dev->struct_mutex);

 	/* We have to maintain this existing ABI... */
 	args->stride = i915_gem_object_get_stride(obj);
 	args->tiling_mode = i915_gem_object_get_tiling(obj);

 err:
 	i915_gem_object_put(obj);
 	return err;
 }

 /**
  * i915_gem_get_tiling_ioctl - IOCTL handler to get tiling mode
  * @dev: DRM device
  * @data: data pointer for the ioctl
  * @file: DRM file for the ioctl call
  *
  * Returns the current tiling mode and required bit 6 swizzling for the object.
  *
  * Called by the user via ioctl.
  *
  * Returns:
  * Zero on success, negative errno on failure.
  */
 int
 i915_gem_get_tiling_ioctl(struct drm_device *dev, void *data,
 			  struct drm_file *file)
 {
 	struct drm_i915_gem_get_tiling *args = data;
 	struct drm_i915_private *dev_priv = to_i915(dev);
 	struct drm_i915_gem_object *obj;
 	int err = -ENOENT;

 	rcu_read_lock();
 	obj = i915_gem_object_lookup_rcu(file, args->handle);
 	if (obj) {
 		args->tiling_mode =
 			READ_ONCE(obj->tiling_and_stride) & TILING_MASK;
 		err = 0;
 	}
 	rcu_read_unlock();
 	if (unlikely(err))
 		return err;

 	switch (args->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;
 	default:
 	case I915_TILING_NONE:
 		args->swizzle_mode = I915_BIT_6_SWIZZLE_NONE;
 		break;
 	}

 	/* Hide bit 17 from the user -- see comment in i915_gem_set_tiling */
 	if (dev_priv->quirks & QUIRK_PIN_SWIZZLED_PAGES)
 		args->phys_swizzle_mode = I915_BIT_6_SWIZZLE_UNKNOWN;
 	else
 		args->phys_swizzle_mode = args->swizzle_mode;
 	if (args->swizzle_mode == I915_BIT_6_SWIZZLE_9_17)
 		args->swizzle_mode = I915_BIT_6_SWIZZLE_9;
 	if (args->swizzle_mode == I915_BIT_6_SWIZZLE_9_10_17)
 		args->swizzle_mode = I915_BIT_6_SWIZZLE_9_10;

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

	/**
	* DOC: buffer object tiling
	*
	* i915_gem_set_tiling_ioctl() and i915_gem_get_tiling_ioctl() is the userspace
	* interface to declare fence register requirements.
	*
	* In principle GEM doesn't care at all about the internal data layout of an
	* object, and hence it also doesn't care about tiling or swizzling. There's two
	* exceptions:
	*
	* - For X and Y tiling the hardware provides detilers for CPU access, so called
	* fences. Since there's only a limited amount of them the kernel must manage
	* these, and therefore userspace must tell the kernel the object tiling if it
	* wants to use fences for detiling.
	* - On gen3 and gen4 platforms have a swizzling pattern for tiled objects which
	* depends upon the physical page frame number. When swapping such objects the
	* page frame number might change and the kernel must be able to fix this up
	* and hence now the tiling. Note that on a subset of platforms with
	* asymmetric memory channel population the swizzling pattern changes in an
	* unknown way, and for those the kernel simply forbids swapping completely.
	*
	* Since neither of this applies for new tiling layouts on modern platforms like
	* W, Ys and Yf tiling GEM only allows object tiling to be set to X or Y tiled.
	* Anything else can be handled in userspace entirely without the kernel's
	* invovlement.
	*/

	/**
	* i915_gem_fence_size - required global GTT size for a fence
	* @i915: i915 device
	* @size: object size
	* @tiling: tiling mode
	* @stride: tiling stride
	*
	* Return the required global GTT size for a fence (view of a tiled object),
	* taking into account potential fence register mapping.
	*/
	u32 i915_gem_fence_size(struct drm_i915_private *i915,
	u32 size, unsigned int tiling, unsigned int stride)
	{
	u32 ggtt_size;

	GEM_BUG_ON(!size);

	if (tiling == I915_TILING_NONE)
	return size;

	GEM_BUG_ON(!stride);

	if (INTEL_GEN(i915) >= 4) {
	stride *= i915_gem_tile_height(tiling);
	GEM_BUG_ON(!IS_ALIGNED(stride, I965_FENCE_PAGE));
	return roundup(size, stride);
	}

	/* Previous chips need a power-of-two fence region when tiling */
	if (IS_GEN3(i915))
	ggtt_size = 1024*1024;
	else
	ggtt_size = 512*1024;

	while (ggtt_size < size)
	ggtt_size <<= 1;

	return ggtt_size;
	}

	/**
	* i915_gem_fence_alignment - required global GTT alignment for a fence
	* @i915: i915 device
	* @size: object size
	* @tiling: tiling mode
	* @stride: tiling stride
	*
	* Return the required global GTT alignment for a fence (a view of a tiled
	* object), taking into account potential fence register mapping.
	*/
	u32 i915_gem_fence_alignment(struct drm_i915_private *i915, u32 size,
	unsigned int tiling, unsigned int stride)
	{
	GEM_BUG_ON(!size);

	/*
	* Minimum alignment is 4k (GTT page size), but might be greater
	* if a fence register is needed for the object.
	*/
	if (tiling == I915_TILING_NONE)
	return I915_GTT_MIN_ALIGNMENT;

	if (INTEL_GEN(i915) >= 4)
	return I965_FENCE_PAGE;

	/*
	* Previous chips need to be aligned to the size of the smallest
	* fence register that can contain the object.
	*/
	return i915_gem_fence_size(i915, size, tiling, stride);
	}

	/* Check pitch constriants for all chips & tiling formats */
	static bool
	i915_tiling_ok(struct drm_i915_gem_object *obj,
	unsigned int tiling, unsigned int stride)
	{
	struct drm_i915_private *i915 = to_i915(obj->base.dev);
	unsigned int tile_width;

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

	if (tiling > I915_TILING_LAST)
	return false;

	/* check maximum stride & object size */
	/* i965+ stores the end address of the gtt mapping in the fence
	* reg, so dont bother to check the size */
	if (INTEL_GEN(i915) >= 7) {
	if (stride / 128 > GEN7_FENCE_MAX_PITCH_VAL)
	return false;
	} else if (INTEL_GEN(i915) >= 4) {
	if (stride / 128 > I965_FENCE_MAX_PITCH_VAL)
	return false;
	} else {
	if (stride > 8192)
	return false;

	if (!is_power_of_2(stride))
	return false;
	}

	if (IS_GEN2(i915) \|\|
	(tiling == I915_TILING_Y && HAS_128_BYTE_Y_TILING(i915)))
	tile_width = 128;
	else
	tile_width = 512;

	if (!stride \|\| !IS_ALIGNED(stride, tile_width))
	return false;

	return true;
	}

	static bool i915_vma_fence_prepare(struct i915_vma *vma,
	int tiling_mode, unsigned int stride)
	{
	struct drm_i915_private *i915 = vma->vm->i915;
	u32 size, alignment;

	if (!i915_vma_is_map_and_fenceable(vma))
	return true;

	size = i915_gem_fence_size(i915, vma->size, tiling_mode, stride);
	if (vma->node.size < size)
	return false;

	alignment = i915_gem_fence_alignment(i915, vma->size, tiling_mode, stride);
	if (!IS_ALIGNED(vma->node.start, alignment))
	return false;

	return true;
	}

	/* Make the current GTT allocation valid for the change in tiling. */
	static int
	i915_gem_object_fence_prepare(struct drm_i915_gem_object *obj,
	int tiling_mode, unsigned int stride)
	{
	struct i915_vma *vma;
	int ret;

	if (tiling_mode == I915_TILING_NONE)
	return 0;

	for_each_ggtt_vma(vma, obj) {
	if (i915_vma_fence_prepare(vma, tiling_mode, stride))
	continue;

	ret = i915_vma_unbind(vma);
	if (ret)
	return ret;
	}

	return 0;
	}

	int
	i915_gem_object_set_tiling(struct drm_i915_gem_object *obj,
	unsigned int tiling, unsigned int stride)
	{
	struct drm_i915_private *i915 = to_i915(obj->base.dev);
	struct i915_vma *vma;
	int err;

	/* Make sure we don't cross-contaminate obj->tiling_and_stride */
	BUILD_BUG_ON(I915_TILING_LAST & STRIDE_MASK);

	GEM_BUG_ON(!i915_tiling_ok(obj, tiling, stride));
	GEM_BUG_ON(!stride ^ (tiling == I915_TILING_NONE));
	lockdep_assert_held(&i915->drm.struct_mutex);

	if ((tiling \| stride) == obj->tiling_and_stride)
	return 0;

	if (i915_gem_object_is_framebuffer(obj))
	return -EBUSY;

	/* We need to rebind the object if its current allocation
	* no longer meets the alignment restrictions for its new
	* tiling mode. Otherwise we can just leave it alone, but
	* need to ensure that any fence register is updated before
	* the next fenced (either through the GTT or by the BLT unit
	* on older GPUs) access.
	*
	* After updating the tiling parameters, we then flag whether
	* we need to update an associated fence register. Note this
	* has to also include the unfenced register the GPU uses
	* whilst executing a fenced command for an untiled object.
	*/

	err = i915_gem_object_fence_prepare(obj, tiling, stride);
	if (err)
	return err;

	i915_gem_object_lock(obj);
	if (i915_gem_object_is_framebuffer(obj)) {
	i915_gem_object_unlock(obj);
	return -EBUSY;
	}

	/* If the memory has unknown (i.e. varying) swizzling, we pin the
	* pages to prevent them being swapped out and causing corruption
	* due to the change in swizzling.
	*/
	mutex_lock(&obj->mm.lock);
	if (i915_gem_object_has_pages(obj) &&
	obj->mm.madv == I915_MADV_WILLNEED &&
	i915->quirks & QUIRK_PIN_SWIZZLED_PAGES) {
	if (tiling == I915_TILING_NONE) {
	GEM_BUG_ON(!obj->mm.quirked);
	__i915_gem_object_unpin_pages(obj);
	obj->mm.quirked = false;
	}
	if (!i915_gem_object_is_tiled(obj)) {
	GEM_BUG_ON(obj->mm.quirked);
	__i915_gem_object_pin_pages(obj);
	obj->mm.quirked = true;
	}
	}
	mutex_unlock(&obj->mm.lock);

	for_each_ggtt_vma(vma, obj) {
	vma->fence_size =
	i915_gem_fence_size(i915, vma->size, tiling, stride);
	vma->fence_alignment =
	i915_gem_fence_alignment(i915,
	vma->size, tiling, stride);

	if (vma->fence)
	vma->fence->dirty = true;
	}

	obj->tiling_and_stride = tiling \| stride;
	i915_gem_object_unlock(obj);

	/* Force the fence to be reacquired for GTT access */
	i915_gem_release_mmap(obj);

	/* Try to preallocate memory required to save swizzling on put-pages */
	if (i915_gem_object_needs_bit17_swizzle(obj)) {
	if (!obj->bit_17) {
	obj->bit_17 = kcalloc(BITS_TO_LONGS(obj->base.size >> PAGE_SHIFT),
	sizeof(long), GFP_KERNEL);
	}
	} else {
	kfree(obj->bit_17);
	obj->bit_17 = NULL;
	}

	return 0;
	}

	/**
	* i915_gem_set_tiling_ioctl - IOCTL handler to set tiling mode
	* @dev: DRM device
	* @data: data pointer for the ioctl
	* @file: DRM file for the ioctl call
	*
	* Sets the tiling mode of an object, returning the required swizzling of
	* bit 6 of addresses in the object.
	*
	* Called by the user via ioctl.
	*
	* Returns:
	* Zero on success, negative errno on failure.
	*/
	int
	i915_gem_set_tiling_ioctl(struct drm_device dev, void data,
	struct drm_file *file)
	{
	struct drm_i915_gem_set_tiling *args = data;
	struct drm_i915_gem_object *obj;
	int err;

	obj = i915_gem_object_lookup(file, args->handle);
	if (!obj)
	return -ENOENT;

	/*
	* The tiling mode of proxy objects is handled by its generator, and
	* not allowed to be changed by userspace.
	*/
	if (i915_gem_object_is_proxy(obj)) {
	err = -ENXIO;
	goto err;
	}

	if (!i915_tiling_ok(obj, args->tiling_mode, args->stride)) {
	err = -EINVAL;
	goto err;
	}

	if (args->tiling_mode == I915_TILING_NONE) {
	args->swizzle_mode = I915_BIT_6_SWIZZLE_NONE;
	args->stride = 0;
	} else {
	if (args->tiling_mode == I915_TILING_X)
	args->swizzle_mode = to_i915(dev)->mm.bit_6_swizzle_x;
	else
	args->swizzle_mode = to_i915(dev)->mm.bit_6_swizzle_y;

	/* Hide bit 17 swizzling from the user. This prevents old Mesa
	* from aborting the application on sw fallbacks to bit 17,
	* and we use the pread/pwrite bit17 paths to swizzle for it.
	* If there was a user that was relying on the swizzle
	* information for drm_intel_bo_map()ed reads/writes this would
	* break it, but we don't have any of those.
	*/
	if (args->swizzle_mode == I915_BIT_6_SWIZZLE_9_17)
	args->swizzle_mode = I915_BIT_6_SWIZZLE_9;
	if (args->swizzle_mode == I915_BIT_6_SWIZZLE_9_10_17)
	args->swizzle_mode = I915_BIT_6_SWIZZLE_9_10;

	/* 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;
	args->stride = 0;
	}
	}

	err = mutex_lock_interruptible(&dev->struct_mutex);
	if (err)
	goto err;

	err = i915_gem_object_set_tiling(obj, args->tiling_mode, args->stride);
	mutex_unlock(&dev->struct_mutex);

	/* We have to maintain this existing ABI... */
	args->stride = i915_gem_object_get_stride(obj);
	args->tiling_mode = i915_gem_object_get_tiling(obj);

	err:
	i915_gem_object_put(obj);
	return err;
	}

	/**
	* i915_gem_get_tiling_ioctl - IOCTL handler to get tiling mode
	* @dev: DRM device
	* @data: data pointer for the ioctl
	* @file: DRM file for the ioctl call
	*
	* Returns the current tiling mode and required bit 6 swizzling for the object.
	*
	* Called by the user via ioctl.
	*
	* Returns:
	* Zero on success, negative errno on failure.
	*/
	int
	i915_gem_get_tiling_ioctl(struct drm_device dev, void data,
	struct drm_file *file)
	{
	struct drm_i915_gem_get_tiling *args = data;
	struct drm_i915_private *dev_priv = to_i915(dev);
	struct drm_i915_gem_object *obj;
	int err = -ENOENT;

	rcu_read_lock();
	obj = i915_gem_object_lookup_rcu(file, args->handle);
	if (obj) {
	args->tiling_mode =
	READ_ONCE(obj->tiling_and_stride) & TILING_MASK;
	err = 0;
	}
	rcu_read_unlock();
	if (unlikely(err))
	return err;

	switch (args->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;
	default:
	case I915_TILING_NONE:
	args->swizzle_mode = I915_BIT_6_SWIZZLE_NONE;
	break;
	}

	/* Hide bit 17 from the user -- see comment in i915_gem_set_tiling */
	if (dev_priv->quirks & QUIRK_PIN_SWIZZLED_PAGES)
	args->phys_swizzle_mode = I915_BIT_6_SWIZZLE_UNKNOWN;
	else
	args->phys_swizzle_mode = args->swizzle_mode;
	if (args->swizzle_mode == I915_BIT_6_SWIZZLE_9_17)
	args->swizzle_mode = I915_BIT_6_SWIZZLE_9;
	if (args->swizzle_mode == I915_BIT_6_SWIZZLE_9_10_17)
	args->swizzle_mode = I915_BIT_6_SWIZZLE_9_10;

	return 0;
	}