For unknown reasons, on gfx12 using multiple entities can causes
random corruption of BOs with DCC.
This workaround seems to prevent the issue until the root cause
is understood and fixed.

Link: https://gitlab.freedesktop.org/drm/amd/-/work_items/5663
Fixes: 3a6f6eeb3db5 ("drm/amdgpu: give ttm entities access to all the sdma 
scheds")
Signed-off-by: Pierre-Eric Pelloux-Prayer <[email protected]>
Reviewed-by: Alex Deucher <[email protected]>
---
 drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c 
b/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
index 3d620ec2937f..e9de5c4b7f63 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
@@ -2367,7 +2367,7 @@ void amdgpu_ttm_fini(struct amdgpu_device *adev)
 void amdgpu_ttm_enable_buffer_funcs(struct amdgpu_device *adev)
 {
        struct ttm_resource_manager *man = ttm_manager_type(&adev->mman.bdev, 
TTM_PL_VRAM);
-       u32 num_clear_entities, num_move_entities;
+       u32 num_clear_entities, num_move_entities, sdma_ip_version;
        int r, i, j;
 
        if (!adev->mman.initialized || amdgpu_in_reset(adev) ||
@@ -2392,6 +2392,12 @@ void amdgpu_ttm_enable_buffer_funcs(struct amdgpu_device 
*adev)
 
        num_clear_entities = MIN(adev->mman.num_buffer_funcs_scheds, 
TTM_NUM_MOVE_FENCES);
        num_move_entities = MIN(adev->mman.num_buffer_funcs_scheds, 
TTM_NUM_MOVE_FENCES);
+        /* TODO: workaround for DCC corruption when moving BOs from multiple 
queues at
+         * the same time: use a single queue until the root cause is 
identified and fixed.
+         */
+       sdma_ip_version = amdgpu_ip_version(adev, SDMA0_HWIP, 0);
+       if (sdma_ip_version == IP_VERSION(7, 0, 0) || sdma_ip_version == 
IP_VERSION(7, 0, 1))
+               num_move_entities = 1;
 
        adev->mman.clear_entities = kcalloc(num_clear_entities,
                                                sizeof(struct 
amdgpu_ttm_buffer_entity),
-- 
2.43.0

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