[PATCH] drm/amdgpu: Fix compute ring 1.0.0 failure after reset

[Andrey Grodzovsky]

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 at amd.com>
---
 drivers/gpu/drm/amd/amdgpu/gfx_v8_0.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/amd/amdgpu/gfx_v8_0.c b/drivers/gpu/drm/amd/amdgpu/gfx_v8_0.c
index b2e1376..02f8ca5 100644
--- a/drivers/gpu/drm/amd/amdgpu/gfx_v8_0.c
+++ b/drivers/gpu/drm/amd/amdgpu/gfx_v8_0.c
@@ -4811,8 +4811,10 @@ 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];
 		r = amdgpu_ring_test_helper(ring);
 	}
-- 
2.7.4