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

[David (Ming Qiang) Wu]

The addition of register read-back in VCN v5.0.1 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_v5_0_1.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/drivers/gpu/drm/amd/amdgpu/vcn_v5_0_1.c b/drivers/gpu/drm/amd/amdgpu/vcn_v5_0_1.c
index 60ee6e02e6ac..edf6d29dccb6 100644
--- a/drivers/gpu/drm/amd/amdgpu/vcn_v5_0_1.c
+++ b/drivers/gpu/drm/amd/amdgpu/vcn_v5_0_1.c
@@ -809,6 +809,11 @@ static int vcn_v5_0_1_start(struct amdgpu_vcn_inst *vinst)
 	WREG32_SOC15(VCN, vcn_inst, regVCN_RB_ENABLE, tmp);
 	fw_shared->sq.queue_mode &= ~(FW_QUEUE_RING_RESET | FW_QUEUE_DPG_HOLD_OFF);
 
+	/* Keeping one read-back to ensure all register writes are done, otherwise
+	 * it may introduce race conditions.
+	 */
+	RREG32_SOC15(VCN, vcn_inst, regUVD_RB_WPTR);
+
 	return 0;
 }
 
-- 
2.49.0