drm/amdgpu: Fix compute ring 1.0.0 failure after reset

Problem: After GPU reset on dGPUs with gfx8 compute ring
1.0.0 fails to pass the ring test. Ring registers inspection
shows that it's active and no hang is observed (rptr == wptr)
No significant diffs were observed between CP_HQD* registers
for the ring in good and bad shape.

Fix: No clear reason why but reversing the order of ring tests
fixes the problem.

Signed-off-by: Andrey Grodzovsky <andrey.grodzovsky@amd.com>
Acked-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

diff --git a/drivers/gpu/drm/amd/amdgpu/gfx_v8_0.c b/drivers/gpu/drm/amd/amdgpu/gfx_v8_0.c
index 3d0f277..617b0c8 100644 (file)
--- a/drivers/gpu/drm/amd/amdgpu/gfx_v8_0.c
+++ b/drivers/gpu/drm/amd/amdgpu/gfx_v8_0.c
@@ -4815,8 +4815,10 @@ static int gfx_v8_0_kcq_resume(struct amdgpu_device *adev)
        if (r)
                goto done;
 
-       /* Test KCQs */
-       for (i = 0; i < adev->gfx.num_compute_rings; i++) {
+       /* Test KCQs - reversing the order of rings seems to fix ring test failure
+        * after GPU reset
+        */
+       for (i = adev->gfx.num_compute_rings - 1; i >= 0; i--) {
                ring = &adev->gfx.compute_ring[i];
                ring->ready = true;
                r = amdgpu_ring_test_ring(ring);