[Intel-gfx] [PATCH] drm/i915: fix vxd392 memory corruption on VLV and >4GB

[Sean V Kelley]

On VLV systems addressing 4GB of memory or greater, memory corruption was seen
when initializing and attempting to render VP8 hardware decode surfaces using
the VXD392 HW IP block.

The VXD MMU has a limitation to addressing only 32bits.  On 64bit kernel and
user space builds this can cause problems for use of that IP block.

When 2G memory is inserted, fw buffer pfn was at 0x5f62b, which is below 4GB.
While for 4GB of memory the fw buffer pfn was 0x162ea9 with a physical address
at 0x162ea9000, above 4GB.

So although the memory is 4GB in the test hardware (Bayleybay CRB), a large
physical region (for example 3G-4G) can be occupied by onboard system
resources.

Enabling ZONE_DMA32 and setting the correct mask DMA for this device
resolves the issue kernel side.

Cc: Jesse Barnes <jbarnes at virtuousgeek.org>
Cc: Alan Cox <alan at linux.intel.com>
Cc: Fei Jiang <fei.jiang at intel.com>
Signed-off-by: Sean V Kelley <sean.v.kelley at intel.com>
---
 drivers/gpu/drm/i915/i915_dma.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/i915/i915_dma.c b/drivers/gpu/drm/i915/i915_dma.c
index e4d2b9f..b8c6efc 100644
--- a/drivers/gpu/drm/i915/i915_dma.c
+++ b/drivers/gpu/drm/i915/i915_dma.c
@@ -1636,7 +1636,7 @@ int i915_driver_load(struct drm_device *dev, unsigned long flags)
 	 * behaviour if any general state is accessed within a page above 4GB,
 	 * which also needs to be handled carefully.
 	 */
-	if (IS_BROADWATER(dev) || IS_CRESTLINE(dev))
+	if (IS_BROADWATER(dev) || IS_CRESTLINE(dev) || IS_VALLEYVIEW(dev))
 		dma_set_coherent_mask(&dev->pdev->dev, DMA_BIT_MASK(32));
 
 	aperture_size = dev_priv->gtt.mappable_end;
-- 
1.9.0