[PATCH v1 1/8] drm/amdgpu: read back register after written

[David (Ming Qiang) Wu]

The addition of register read-back in VCN v1.0 is intended to prevent
potential race conditions.

Signed-off-by: David (Ming Qiang) Wu <David.Wu3 at amd.com>
---
 drivers/gpu/drm/amd/amdgpu/vcn_v1_0.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/drivers/gpu/drm/amd/amdgpu/vcn_v1_0.c b/drivers/gpu/drm/amd/amdgpu/vcn_v1_0.c
index 21b57c29bf7d..f56b623713c9 100644
--- a/drivers/gpu/drm/amd/amdgpu/vcn_v1_0.c
+++ b/drivers/gpu/drm/amd/amdgpu/vcn_v1_0.c
@@ -1009,6 +1009,11 @@ static int vcn_v1_0_start_spg_mode(struct amdgpu_vcn_inst *vinst)
 
 	jpeg_v1_0_start(adev, 0);
 
+	/* Keeping one read-back to ensure all register writes are done, otherwise
+	 * it may introduce race conditions
+	 */
+	RREG32_SOC15(UVD, 0, mmUVD_RBC_RB_WPTR);
+
 	return 0;
 }
 
@@ -1154,6 +1159,11 @@ static int vcn_v1_0_start_dpg_mode(struct amdgpu_vcn_inst *vinst)
 
 	jpeg_v1_0_start(adev, 1);
 
+	/* Keeping one read-back to ensure all register writes are done, otherwise
+	 * it may introduce race conditions
+	 */
+	RREG32_SOC15(UVD, 0, mmUVD_RBC_RB_WPTR);
+
 	return 0;
 }
 
-- 
2.49.0