[PATCH] gpu/drm: Remove TTM_PL_FLAG_WC of VRAM to fix writecombine issue for Loongson64

[Tiezhu Yang]

Loongson processors have a writecombine issue that maybe failed to
write back framebuffer used with ATI Radeon or AMD GPU at times,
after commit 8a08e50cee66 ("drm: Permit video-buffers writecombine
mapping for MIPS"), there exists some errors such as blurred screen
and lockup, and so on.

Remove the flag TTM_PL_FLAG_WC of VRAM to fix writecombine issue for
Loongson64 to work well with ATI Radeon or AMD GPU, and it has no any
influence on the other platforms.

[   60.958721] radeon 0000:03:00.0: ring 0 stalled for more than 10079msec
[   60.965315] radeon 0000:03:00.0: GPU lockup (current fence id 0x0000000000000112 last fence id 0x000000000000011d on ring 0)
[   60.976525] radeon 0000:03:00.0: ring 3 stalled for more than 10086msec
[   60.983156] radeon 0000:03:00.0: GPU lockup (current fence id 0x0000000000000374 last fence id 0x00000000000003a8 on ring 3)

Signed-off-by: Tiezhu Yang <yangtiezhu at loongson.cn>
---
 drivers/gpu/drm/amd/amdgpu/amdgpu_object.c |  7 +++++--
 drivers/gpu/drm/radeon/radeon_object.c     | 20 ++++++++++++++------
 2 files changed, 19 insertions(+), 8 deletions(-)

diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_object.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_object.c
index 5ac7b55..9f785f6 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_object.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_object.c
@@ -136,8 +136,11 @@ void amdgpu_bo_placement_from_domain(struct amdgpu_bo *abo, u32 domain)
 
 		places[c].fpfn = 0;
 		places[c].lpfn = 0;
-		places[c].flags = TTM_PL_FLAG_WC | TTM_PL_FLAG_UNCACHED |
-			TTM_PL_FLAG_VRAM;
+		if (IS_ENABLED(CONFIG_MACH_LOONGSON64))
+			places[c].flags = TTM_PL_FLAG_UNCACHED | TTM_PL_FLAG_VRAM;
+		else
+			places[c].flags = TTM_PL_FLAG_WC | TTM_PL_FLAG_UNCACHED |
+					  TTM_PL_FLAG_VRAM;
 
 		if (flags & AMDGPU_GEM_CREATE_CPU_ACCESS_REQUIRED)
 			places[c].lpfn = visible_pfn;
diff --git a/drivers/gpu/drm/radeon/radeon_object.c b/drivers/gpu/drm/radeon/radeon_object.c
index f3dee01..c6cede6 100644
--- a/drivers/gpu/drm/radeon/radeon_object.c
+++ b/drivers/gpu/drm/radeon/radeon_object.c
@@ -112,15 +112,23 @@ void radeon_ttm_placement_from_domain(struct radeon_bo *rbo, u32 domain)
 		    rbo->rdev->mc.visible_vram_size < rbo->rdev->mc.real_vram_size) {
 			rbo->placements[c].fpfn =
 				rbo->rdev->mc.visible_vram_size >> PAGE_SHIFT;
-			rbo->placements[c++].flags = TTM_PL_FLAG_WC |
-						     TTM_PL_FLAG_UNCACHED |
-						     TTM_PL_FLAG_VRAM;
+			if (IS_ENABLED(CONFIG_MACH_LOONGSON64))
+				rbo->placements[c++].flags = TTM_PL_FLAG_UNCACHED |
+							     TTM_PL_FLAG_VRAM;
+			else
+				rbo->placements[c++].flags = TTM_PL_FLAG_WC |
+							     TTM_PL_FLAG_UNCACHED |
+							     TTM_PL_FLAG_VRAM;
 		}
 
 		rbo->placements[c].fpfn = 0;
-		rbo->placements[c++].flags = TTM_PL_FLAG_WC |
-					     TTM_PL_FLAG_UNCACHED |
-					     TTM_PL_FLAG_VRAM;
+		if (IS_ENABLED(CONFIG_MACH_LOONGSON64))
+			rbo->placements[c++].flags = TTM_PL_FLAG_UNCACHED |
+						     TTM_PL_FLAG_VRAM;
+		else
+			rbo->placements[c++].flags = TTM_PL_FLAG_WC |
+						     TTM_PL_FLAG_UNCACHED |
+						     TTM_PL_FLAG_VRAM;
 	}
 
 	if (domain & RADEON_GEM_DOMAIN_GTT) {
-- 
2.1.0