[PATCH 11/12] drm/i915/bdw: Use scratch page table for GEN8 PPGTT

[Ben Widawsky <benjamin.widawsky@linux.intel.com>]

From: Ben Widawsky <benjamin.widawsky@intel.com>

I'm not clear if the hardware is still subject to the same prefetching
issues that made us use a scratch page in the first place. In either
case, we're using garbage with the current code (we will end up using
offset 0).

This may be the cause of our current gem_cpu_reloc regression with
PPGTT. I cannot test it at the moment.

Signed-off-by: Ben Widawsky <ben@bwidawsk.net>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
[BDW 3.14 backport]
Cc: stable@vger.kernel.org
Signed-off-by: Ben Widawsky <ben@bwidawsk.net>
---
 drivers/gpu/drm/i915/i915_gem_gtt.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/gpu/drm/i915/i915_gem_gtt.c b/drivers/gpu/drm/i915/i915_gem_gtt.c
index 40a2b36..8cc9398 100644
--- a/drivers/gpu/drm/i915/i915_gem_gtt.c
+++ b/drivers/gpu/drm/i915/i915_gem_gtt.c
@@ -359,6 +359,7 @@ static void gen8_ppgtt_cleanup(struct i915_address_space *vm)
  **/
 static int gen8_ppgtt_init(struct i915_hw_ppgtt *ppgtt, uint64_t size)
 {
+	struct drm_i915_private *dev_priv = ppgtt->base.dev->dev_private;
 	struct page *pt_pages;
 	int i, j, ret = -ENOMEM;
 	const int max_pdp = DIV_ROUND_UP(size, 1 << 30);
@@ -389,6 +390,7 @@ static int gen8_ppgtt_init(struct i915_hw_ppgtt *ppgtt, uint64_t size)
 	ppgtt->base.clear_range = gen8_ppgtt_clear_range;
 	ppgtt->base.insert_entries = gen8_ppgtt_insert_entries;
 	ppgtt->base.cleanup = gen8_ppgtt_cleanup;
+	ppgtt->base.scratch = dev_priv->gtt.base.scratch;
 	ppgtt->base.start = 0;
 	ppgtt->base.total = ppgtt->num_pt_pages * GEN8_PTES_PER_PAGE * PAGE_SIZE;
 
-- 
1.9.1