drm/i915: Split out i915_vma.c

As a side product, had to split two other files;
- i915_gem_fence_reg.h
- i915_gem_object.h (only parts that needed immediate untanglement)

I tried to move code in as big chunks as possible, to make review
easier. i915_vma_compare was moved to a header temporarily.

v2:
- Use i915_gem_fence_reg.{c,h}

v3:
- Rebased

v4:
- Fix building when DEBUG_GEM is enabled by reordering a bit.

Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Acked-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Signed-off-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1478861034-30643-1-git-send-email-joonas.lahtinen@linux.intel.com

1 files changed, 716 insertions, 0 deletions

diff --git a/drivers/gpu/drm/i915/i915_gem_fence_reg.c b/drivers/gpu/drm/i915/i915_gem_fence_reg.c
new file mode 100644
index 000000000000..cd59dbc6588c
--- /dev/null
+++ b/drivers/gpu/drm/i915/i915_gem_fence_reg.c
@@ -0,0 +1,716 @@
+/*
+ * Copyright © 2008-2015 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.
+ */
+
+#include <drm/drmP.h>
+#include <drm/i915_drm.h>
+#include "i915_drv.h"
+
+/**
+ * DOC: fence register handling
+ *
+ * Important to avoid confusions: "fences" in the i915 driver are not execution
+ * fences used to track command completion but hardware detiler objects which
+ * wrap a given range of the global GTT. Each platform has only a fairly limited
+ * set of these objects.
+ *
+ * Fences are used to detile GTT memory mappings. They're also connected to the
+ * hardware frontbuffer render tracking and hence interact with frontbuffer
+ * compression. Furthermore on older platforms fences are required for tiled
+ * objects used by the display engine. They can also be used by the render
+ * engine - they're required for blitter commands and are optional for render
+ * commands. But on gen4+ both display (with the exception of fbc) and rendering
+ * have their own tiling state bits and don't need fences.
+ *
+ * Also note that fences only support X and Y tiling and hence can't be used for
+ * the fancier new tiling formats like W, Ys and Yf.
+ *
+ * Finally note that because fences are such a restricted resource they're
+ * dynamically associated with objects. Furthermore fence state is committed to
+ * the hardware lazily to avoid unnecessary stalls on gen2/3. Therefore code must
+ * explicitly call i915_gem_object_get_fence() to synchronize fencing status
+ * for cpu access. Also note that some code wants an unfenced view, for those
+ * cases the fence can be removed forcefully with i915_gem_object_put_fence().
+ *
+ * Internally these functions will synchronize with userspace access by removing
+ * CPU ptes into GTT mmaps (not the GTT ptes themselves) as needed.
+ */
+
+#define pipelined 0
+
+static void i965_write_fence_reg(struct drm_i915_fence_reg *fence,
+				 struct i915_vma *vma)
+{
+	i915_reg_t fence_reg_lo, fence_reg_hi;
+	int fence_pitch_shift;
+	u64 val;
+
+	if (INTEL_INFO(fence->i915)->gen >= 6) {
+		fence_reg_lo = FENCE_REG_GEN6_LO(fence->id);
+		fence_reg_hi = FENCE_REG_GEN6_HI(fence->id);
+		fence_pitch_shift = GEN6_FENCE_PITCH_SHIFT;
+
+	} else {
+		fence_reg_lo = FENCE_REG_965_LO(fence->id);
+		fence_reg_hi = FENCE_REG_965_HI(fence->id);
+		fence_pitch_shift = I965_FENCE_PITCH_SHIFT;
+	}
+
+	val = 0;
+	if (vma) {
+		unsigned int tiling = i915_gem_object_get_tiling(vma->obj);
+		bool is_y_tiled = tiling == I915_TILING_Y;
+		unsigned int stride = i915_gem_object_get_stride(vma->obj);
+		u32 row_size = stride * (is_y_tiled ? 32 : 8);
+		u32 size = rounddown((u32)vma->node.size, row_size);
+
+		val = ((vma->node.start + size - 4096) & 0xfffff000) << 32;
+		val |= vma->node.start & 0xfffff000;
+		val |= (u64)((stride / 128) - 1) << fence_pitch_shift;
+		if (is_y_tiled)
+			val |= BIT(I965_FENCE_TILING_Y_SHIFT);
+		val |= I965_FENCE_REG_VALID;
+	}
+
+	if (!pipelined) {
+		struct drm_i915_private *dev_priv = fence->i915;
+
+		/* To w/a incoherency with non-atomic 64-bit register updates,
+		 * we split the 64-bit update into two 32-bit writes. In order
+		 * for a partial fence not to be evaluated between writes, we
+		 * precede the update with write to turn off the fence register,
+		 * and only enable the fence as the last step.
+		 *
+		 * For extra levels of paranoia, we make sure each step lands
+		 * before applying the next step.
+		 */
+		I915_WRITE(fence_reg_lo, 0);
+		POSTING_READ(fence_reg_lo);
+
+		I915_WRITE(fence_reg_hi, upper_32_bits(val));
+		I915_WRITE(fence_reg_lo, lower_32_bits(val));
+		POSTING_READ(fence_reg_lo);
+	}
+}
+
+static void i915_write_fence_reg(struct drm_i915_fence_reg *fence,
+				 struct i915_vma *vma)
+{
+	u32 val;
+
+	val = 0;
+	if (vma) {
+		unsigned int tiling = i915_gem_object_get_tiling(vma->obj);
+		bool is_y_tiled = tiling == I915_TILING_Y;
+		unsigned int stride = i915_gem_object_get_stride(vma->obj);
+		int pitch_val;
+		int tile_width;
+
+		WARN((vma->node.start & ~I915_FENCE_START_MASK) ||
+		     !is_power_of_2(vma->node.size) ||
+		     (vma->node.start & (vma->node.size - 1)),
+		     "object 0x%08llx [fenceable? %d] not 1M or pot-size (0x%08llx) aligned\n",
+		     vma->node.start,
+		     i915_vma_is_map_and_fenceable(vma),
+		     vma->node.size);
+
+		if (is_y_tiled && HAS_128_BYTE_Y_TILING(fence->i915))
+			tile_width = 128;
+		else
+			tile_width = 512;
+
+		/* Note: pitch better be a power of two tile widths */
+		pitch_val = stride / tile_width;
+		pitch_val = ffs(pitch_val) - 1;
+
+		val = vma->node.start;
+		if (is_y_tiled)
+			val |= BIT(I830_FENCE_TILING_Y_SHIFT);
+		val |= I915_FENCE_SIZE_BITS(vma->node.size);
+		val |= pitch_val << I830_FENCE_PITCH_SHIFT;
+		val |= I830_FENCE_REG_VALID;
+	}
+
+	if (!pipelined) {
+		struct drm_i915_private *dev_priv = fence->i915;
+		i915_reg_t reg = FENCE_REG(fence->id);
+
+		I915_WRITE(reg, val);
+		POSTING_READ(reg);
+	}
+}
+
+static void i830_write_fence_reg(struct drm_i915_fence_reg *fence,
+				 struct i915_vma *vma)
+{
+	u32 val;
+
+	val = 0;
+	if (vma) {
+		unsigned int tiling = i915_gem_object_get_tiling(vma->obj);
+		bool is_y_tiled = tiling == I915_TILING_Y;
+		unsigned int stride = i915_gem_object_get_stride(vma->obj);
+		u32 pitch_val;
+
+		WARN((vma->node.start & ~I830_FENCE_START_MASK) ||
+		     !is_power_of_2(vma->node.size) ||
+		     (vma->node.start & (vma->node.size - 1)),
+		     "object 0x%08llx not 512K or pot-size 0x%08llx aligned\n",
+		     vma->node.start, vma->node.size);
+
+		pitch_val = stride / 128;
+		pitch_val = ffs(pitch_val) - 1;
+
+		val = vma->node.start;
+		if (is_y_tiled)
+			val |= BIT(I830_FENCE_TILING_Y_SHIFT);
+		val |= I830_FENCE_SIZE_BITS(vma->node.size);
+		val |= pitch_val << I830_FENCE_PITCH_SHIFT;
+		val |= I830_FENCE_REG_VALID;
+	}
+
+	if (!pipelined) {
+		struct drm_i915_private *dev_priv = fence->i915;
+		i915_reg_t reg = FENCE_REG(fence->id);
+
+		I915_WRITE(reg, val);
+		POSTING_READ(reg);
+	}
+}
+
+static void fence_write(struct drm_i915_fence_reg *fence,
+			struct i915_vma *vma)
+{
+	/* Previous access through the fence register is marshalled by
+	 * the mb() inside the fault handlers (i915_gem_release_mmaps)
+	 * and explicitly managed for internal users.
+	 */
+
+	if (IS_GEN2(fence->i915))
+		i830_write_fence_reg(fence, vma);
+	else if (IS_GEN3(fence->i915))
+		i915_write_fence_reg(fence, vma);
+	else
+		i965_write_fence_reg(fence, vma);
+
+	/* Access through the fenced region afterwards is
+	 * ordered by the posting reads whilst writing the registers.
+	 */
+
+	fence->dirty = false;
+}
+
+static int fence_update(struct drm_i915_fence_reg *fence,
+			struct i915_vma *vma)
+{
+	int ret;
+
+	if (vma) {
+		if (!i915_vma_is_map_and_fenceable(vma))
+			return -EINVAL;
+
+		if (WARN(!i915_gem_object_get_stride(vma->obj) ||
+			 !i915_gem_object_get_tiling(vma->obj),
+			 "bogus fence setup with stride: 0x%x, tiling mode: %i\n",
+			 i915_gem_object_get_stride(vma->obj),
+			 i915_gem_object_get_tiling(vma->obj)))
+			return -EINVAL;
+
+		ret = i915_gem_active_retire(&vma->last_fence,
+					     &vma->obj->base.dev->struct_mutex);
+		if (ret)
+			return ret;
+	}
+
+	if (fence->vma) {
+		ret = i915_gem_active_retire(&fence->vma->last_fence,
+				      &fence->vma->obj->base.dev->struct_mutex);
+		if (ret)
+			return ret;
+	}
+
+	if (fence->vma && fence->vma != vma) {
+		/* Ensure that all userspace CPU access is completed before
+		 * stealing the fence.
+		 */
+		i915_gem_release_mmap(fence->vma->obj);
+
+		fence->vma->fence = NULL;
+		fence->vma = NULL;
+
+		list_move(&fence->link, &fence->i915->mm.fence_list);
+	}
+
+	fence_write(fence, vma);
+
+	if (vma) {
+		if (fence->vma != vma) {
+			vma->fence = fence;
+			fence->vma = vma;
+		}
+
+		list_move_tail(&fence->link, &fence->i915->mm.fence_list);
+	}
+
+	return 0;
+}
+
+/**
+ * i915_vma_put_fence - force-remove fence for a VMA
+ * @vma: vma to map linearly (not through a fence reg)
+ *
+ * This function force-removes any fence from the given object, which is useful
+ * if the kernel wants to do untiled GTT access.
+ *
+ * Returns:
+ *
+ * 0 on success, negative error code on failure.
+ */
+int
+i915_vma_put_fence(struct i915_vma *vma)
+{
+	struct drm_i915_fence_reg *fence = vma->fence;
+
+	assert_rpm_wakelock_held(to_i915(vma->vm->dev));
+
+	if (!fence)
+		return 0;
+
+	if (fence->pin_count)
+		return -EBUSY;
+
+	return fence_update(fence, NULL);
+}
+
+static struct drm_i915_fence_reg *fence_find(struct drm_i915_private *dev_priv)
+{
+	struct drm_i915_fence_reg *fence;
+
+	list_for_each_entry(fence, &dev_priv->mm.fence_list, link) {
+		if (fence->pin_count)
+			continue;
+
+		return fence;
+	}
+
+	/* Wait for completion of pending flips which consume fences */
+	if (intel_has_pending_fb_unpin(&dev_priv->drm))
+		return ERR_PTR(-EAGAIN);
+
+	return ERR_PTR(-EDEADLK);
+}
+
+/**
+ * i915_vma_get_fence - set up fencing for a vma
+ * @vma: vma to map through a fence reg
+ *
+ * When mapping objects through the GTT, userspace wants to be able to write
+ * to them without having to worry about swizzling if the object is tiled.
+ * This function walks the fence regs looking for a free one for @obj,
+ * stealing one if it can't find any.
+ *
+ * It then sets up the reg based on the object's properties: address, pitch
+ * and tiling format.
+ *
+ * For an untiled surface, this removes any existing fence.
+ *
+ * Returns:
+ *
+ * 0 on success, negative error code on failure.
+ */
+int
+i915_vma_get_fence(struct i915_vma *vma)
+{
+	struct drm_i915_fence_reg *fence;
+	struct i915_vma *set = i915_gem_object_is_tiled(vma->obj) ? vma : NULL;
+
+	/* Note that we revoke fences on runtime suspend. Therefore the user
+	 * must keep the device awake whilst using the fence.
+	 */
+	assert_rpm_wakelock_held(to_i915(vma->vm->dev));
+
+	/* Just update our place in the LRU if our fence is getting reused. */
+	if (vma->fence) {
+		fence = vma->fence;
+		if (!fence->dirty) {
+			list_move_tail(&fence->link,
+				       &fence->i915->mm.fence_list);
+			return 0;
+		}
+	} else if (set) {
+		fence = fence_find(to_i915(vma->vm->dev));
+		if (IS_ERR(fence))
+			return PTR_ERR(fence);
+	} else
+		return 0;
+
+	return fence_update(fence, set);
+}
+
+/**
+ * i915_gem_restore_fences - restore fence state
+ * @dev: DRM device
+ *
+ * Restore the hw fence state to match the software tracking again, to be called
+ * after a gpu reset and on resume. Note that on runtime suspend we only cancel
+ * the fences, to be reacquired by the user later.
+ */
+void i915_gem_restore_fences(struct drm_device *dev)
+{
+	struct drm_i915_private *dev_priv = to_i915(dev);
+	int i;
+
+	for (i = 0; i < dev_priv->num_fence_regs; i++) {
+		struct drm_i915_fence_reg *reg = &dev_priv->fence_regs[i];
+		struct i915_vma *vma = reg->vma;
+
+		/*
+		 * Commit delayed tiling changes if we have an object still
+		 * attached to the fence, otherwise just clear the fence.
+		 */
+		if (vma && !i915_gem_object_is_tiled(vma->obj)) {
+			GEM_BUG_ON(!reg->dirty);
+			GEM_BUG_ON(!list_empty(&vma->obj->userfault_link));
+
+			list_move(&reg->link, &dev_priv->mm.fence_list);
+			vma->fence = NULL;
+			vma = NULL;
+		}
+
+		fence_write(reg, vma);
+		reg->vma = vma;
+	}
+}
+
+/**
+ * DOC: tiling swizzling details
+ *
+ * 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 object 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.
+ */
+
+/**
+ * i915_gem_detect_bit_6_swizzle - detect bit 6 swizzling pattern
+ * @dev: DRM device
+ *
+ * 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)
+{
+	struct drm_i915_private *dev_priv = to_i915(dev);
+	uint32_t swizzle_x = I915_BIT_6_SWIZZLE_UNKNOWN;
+	uint32_t swizzle_y = I915_BIT_6_SWIZZLE_UNKNOWN;
+
+	if (INTEL_GEN(dev_priv) >= 8 || IS_VALLEYVIEW(dev_priv)) {
+		/*
+		 * On BDW+, swizzling is not used. We leave the CPU memory
+		 * controller in charge of optimizing memory accesses without
+		 * the extra address manipulation GPU side.
+		 *
+		 * VLV and CHV don't have GPU swizzling.
+		 */
+		swizzle_x = I915_BIT_6_SWIZZLE_NONE;
+		swizzle_y = I915_BIT_6_SWIZZLE_NONE;
+	} else if (INTEL_INFO(dev)->gen >= 6) {
+		if (dev_priv->preserve_bios_swizzle) {
+			if (I915_READ(DISP_ARB_CTL) &
+			    DISP_TILE_SURFACE_SWIZZLING) {
+				swizzle_x = I915_BIT_6_SWIZZLE_9_10;
+				swizzle_y = I915_BIT_6_SWIZZLE_9;
+			} else {
+				swizzle_x = I915_BIT_6_SWIZZLE_NONE;
+				swizzle_y = I915_BIT_6_SWIZZLE_NONE;
+			}
+		} else {
+			uint32_t dimm_c0, dimm_c1;
+			dimm_c0 = I915_READ(MAD_DIMM_C0);
+			dimm_c1 = I915_READ(MAD_DIMM_C1);
+			dimm_c0 &= MAD_DIMM_A_SIZE_MASK | MAD_DIMM_B_SIZE_MASK;
+			dimm_c1 &= MAD_DIMM_A_SIZE_MASK | MAD_DIMM_B_SIZE_MASK;
+			/* Enable swizzling when the channels are populated
+			 * with identically sized dimms. We don't need to check
+			 * the 3rd channel because no cpu with gpu attached
+			 * ships in that configuration. Also, swizzling only
+			 * makes sense for 2 channels anyway. */
+			if (dimm_c0 == dimm_c1) {
+				swizzle_x = I915_BIT_6_SWIZZLE_9_10;
+				swizzle_y = I915_BIT_6_SWIZZLE_9;
+			} else {
+				swizzle_x = I915_BIT_6_SWIZZLE_NONE;
+				swizzle_y = I915_BIT_6_SWIZZLE_NONE;
+			}
+		}
+	} else if (IS_GEN5(dev_priv)) {
+		/* On Ironlake whatever DRAM config, GPU always do
+		 * same swizzling setup.
+		 */
+		swizzle_x = I915_BIT_6_SWIZZLE_9_10;
+		swizzle_y = I915_BIT_6_SWIZZLE_9;
+	} else if (IS_GEN2(dev_priv)) {
+		/* 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_MOBILE(dev_priv) || (IS_GEN3(dev_priv) &&
+		   !IS_G33(dev_priv))) {
+		uint32_t dcc;
+
+		/* On 9xx chipsets, channel interleave by the CPU is
+		 * determined by DCC.  For single-channel, neither the CPU
+		 * nor the GPU do swizzling.  For dual channel interleaved,
+		 * the GPU's interleave is bit 9 and 10 for X tiled, and bit
+		 * 9 for Y tiled.  The CPU's interleave is independent, and
+		 * can be based on either bit 11 (haven't seen this yet) or
+		 * bit 17 (common).
+		 */
+		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 (dcc & DCC_CHANNEL_XOR_DISABLE) {
+				/* This is the base swizzling by the GPU for
+				 * tiled buffers.
+				 */
+				swizzle_x = I915_BIT_6_SWIZZLE_9_10;
+				swizzle_y = I915_BIT_6_SWIZZLE_9;
+			} else if ((dcc & DCC_CHANNEL_XOR_BIT_17) == 0) {
+				/* Bit 11 swizzling by the CPU in addition. */
+				swizzle_x = I915_BIT_6_SWIZZLE_9_10_11;
+				swizzle_y = I915_BIT_6_SWIZZLE_9_11;
+			} else {
+				/* Bit 17 swizzling by the CPU in addition. */
+				swizzle_x = I915_BIT_6_SWIZZLE_9_10_17;
+				swizzle_y = I915_BIT_6_SWIZZLE_9_17;
+			}
+			break;
+		}
+
+		/* check for L-shaped memory aka modified enhanced addressing */
+		if (IS_GEN4(dev_priv) &&
+		    !(I915_READ(DCC2) & DCC2_MODIFIED_ENHANCED_DISABLE)) {
+			swizzle_x = I915_BIT_6_SWIZZLE_UNKNOWN;
+			swizzle_y = I915_BIT_6_SWIZZLE_UNKNOWN;
+		}
+
+		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.
+		 *
+		 * Reports indicate that the swizzling actually
+		 * varies depending upon page placement inside the
+		 * channels, i.e. we see swizzled pages where the
+		 * banks of memory are paired and unswizzled on the
+		 * uneven portion, so leave that as unknown.
+		 */
+		if (I915_READ16(C0DRB3) == I915_READ16(C1DRB3)) {
+			swizzle_x = I915_BIT_6_SWIZZLE_9_10;
+			swizzle_y = I915_BIT_6_SWIZZLE_9;
+		}
+	}
+
+	if (swizzle_x == I915_BIT_6_SWIZZLE_UNKNOWN ||
+	    swizzle_y == I915_BIT_6_SWIZZLE_UNKNOWN) {
+		/* Userspace likes to explode if it sees unknown swizzling,
+		 * so lie. We will finish the lie when reporting through
+		 * the get-tiling-ioctl by reporting the physical swizzle
+		 * mode as unknown instead.
+		 *
+		 * As we don't strictly know what the swizzling is, it may be
+		 * bit17 dependent, and so we need to also prevent the pages
+		 * from being moved.
+		 */
+		dev_priv->quirks |= QUIRK_PIN_SWIZZLED_PAGES;
+		swizzle_x = I915_BIT_6_SWIZZLE_NONE;
+		swizzle_y = I915_BIT_6_SWIZZLE_NONE;
+	}
+
+	dev_priv->mm.bit_6_swizzle_x = swizzle_x;
+	dev_priv->mm.bit_6_swizzle_y = swizzle_y;
+}
+
+/*
+ * Swap every 64 bytes of this page around, to account for it having a new
+ * bit 17 of its physical address and therefore being interpreted differently
+ * by the GPU.
+ */
+static void
+i915_gem_swizzle_page(struct page *page)
+{
+	char temp[64];
+	char *vaddr;
+	int i;
+
+	vaddr = kmap(page);
+
+	for (i = 0; i < PAGE_SIZE; i += 128) {
+		memcpy(temp, &vaddr[i], 64);
+		memcpy(&vaddr[i], &vaddr[i + 64], 64);
+		memcpy(&vaddr[i + 64], temp, 64);
+	}
+
+	kunmap(page);
+}
+
+/**
+ * i915_gem_object_do_bit_17_swizzle - fixup bit 17 swizzling
+ * @obj: i915 GEM buffer object
+ * @pages: the scattergather list of physical pages
+ *
+ * This function fixes up the swizzling in case any page frame number for this
+ * object has changed in bit 17 since that state has been saved with
+ * i915_gem_object_save_bit_17_swizzle().
+ *
+ * This is called when pinning backing storage again, since the kernel is free
+ * to move unpinned backing storage around (either by directly moving pages or
+ * by swapping them out and back in again).
+ */
+void
+i915_gem_object_do_bit_17_swizzle(struct drm_i915_gem_object *obj,
+				  struct sg_table *pages)
+{
+	struct sgt_iter sgt_iter;
+	struct page *page;
+	int i;
+
+	if (obj->bit_17 == NULL)
+		return;
+
+	i = 0;
+	for_each_sgt_page(page, sgt_iter, pages) {
+		char new_bit_17 = page_to_phys(page) >> 17;
+		if ((new_bit_17 & 0x1) != (test_bit(i, obj->bit_17) != 0)) {
+			i915_gem_swizzle_page(page);
+			set_page_dirty(page);
+		}
+		i++;
+	}
+}
+
+/**
+ * i915_gem_object_save_bit_17_swizzle - save bit 17 swizzling
+ * @obj: i915 GEM buffer object
+ * @pages: the scattergather list of physical pages
+ *
+ * This function saves the bit 17 of each page frame number so that swizzling
+ * can be fixed up later on with i915_gem_object_do_bit_17_swizzle(). This must
+ * be called before the backing storage can be unpinned.
+ */
+void
+i915_gem_object_save_bit_17_swizzle(struct drm_i915_gem_object *obj,
+				    struct sg_table *pages)
+{
+	const unsigned int page_count = obj->base.size >> PAGE_SHIFT;
+	struct sgt_iter sgt_iter;
+	struct page *page;
+	int i;
+
+	if (obj->bit_17 == NULL) {
+		obj->bit_17 = kcalloc(BITS_TO_LONGS(page_count),
+				      sizeof(long), GFP_KERNEL);
+		if (obj->bit_17 == NULL) {
+			DRM_ERROR("Failed to allocate memory for bit 17 "
+				  "record\n");
+			return;
+		}
+	}
+
+	i = 0;
+
+	for_each_sgt_page(page, sgt_iter, pages) {
+		if (page_to_phys(page) & (1 << 17))
+			__set_bit(i, obj->bit_17);
+		else
+			__clear_bit(i, obj->bit_17);
+		i++;
+	}
+}