drm/amdgpu: fix ring test failure issue during s3 in vce 3.0 (V2)

commit ce0e22f5 upstream.

[What]
vce ring test fails consistently during resume in s3 cycle, due to
mismatch read & write pointers.
On debug/analysis its found that rptr to be compared is not being
correctly updated/read, which leads to this failure.
Below is the failure signature:
	[drm:amdgpu_vce_ring_test_ring] *ERROR* amdgpu: ring 12 test failed
	[drm:amdgpu_device_ip_resume_phase2] *ERROR* resume of IP block <vce_v3_0> failed -110
	[drm:amdgpu_device_resume] *ERROR* amdgpu_device_ip_resume failed (-110).

[How]
fetch rptr appropriately, meaning move its read location further down
in the code flow.
With this patch applied the s3 failure is no more seen for >5k s3 cycles,
which otherwise is pretty consistent.

V2: remove reduntant fetch of rptr
Signed-off-by: Louis Li <Ching-shih.Li@amd.com>
Reviewed-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Cc: stable@vger.kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/gpu/drm/amd/amdgpu/amdgpu_vce.c

@@ -1072,7 +1072,7 @@ void amdgpu_vce_ring_emit_fence(struct amdgpu_ring *ring, u64 addr, u64 seq,
 int amdgpu_vce_ring_test_ring(struct amdgpu_ring *ring)
 {
 	struct amdgpu_device *adev = ring->adev;
-	uint32_t rptr = amdgpu_ring_get_rptr(ring);
+	uint32_t rptr;
 	unsigned i;
 	int r, timeout = adev->usec_timeout;
 
@@ -1084,6 +1084,8 @@ int amdgpu_vce_ring_test_ring(struct amdgpu_ring *ring)
 	if (r)
 		return r;
 
+	rptr = amdgpu_ring_get_rptr(ring);
+
 	amdgpu_ring_write(ring, VCE_CMD_END);
 	amdgpu_ring_commit(ring);