commit 108aa376ae52e634f6465424554fa9319c0a7a61
Author: Michel Dänzer <michel.daenzer@amd.com>
Date:   Fri Oct 10 18:01:18 2014 +0900

    drm/radeon: Ignore RADEON_GEM_GTT_WC on Kabini and Aruba

diff --git a/drivers/gpu/drm/radeon/radeon_object.c b/drivers/gpu/drm/radeon/radeon_object.c
index 7f3b1e1..aea7c6e 100644
--- a/drivers/gpu/drm/radeon/radeon_object.c
+++ b/drivers/gpu/drm/radeon/radeon_object.c
@@ -235,6 +235,10 @@ int radeon_bo_create(struct radeon_device *rdev,
 	if (!(rdev->flags & RADEON_IS_PCIE))
 		bo->flags &= ~(RADEON_GEM_GTT_WC | RADEON_GEM_GTT_UC);
 
+	/* XXX: Write-combined CPU mappings of GTT seem broken on Kabini and Aruba */
+	if (rdev->family == CHIP_KABINI || rdev->family == CHIP_ARUBA)
+		bo->flags &= ~RADEON_GEM_GTT_WC;
+
 	radeon_ttm_placement_from_domain(bo, domain);
 	/* Kernel allocation are uninterruptible */
 	down_read(&rdev->pm.mclk_lock);