The addition of register read-back in VCN v4.0.3 is intended to prevent potential race conditions.
Signed-off-by: David (Ming Qiang) Wu <[email protected]> --- drivers/gpu/drm/amd/amdgpu/vcn_v4_0_3.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/drivers/gpu/drm/amd/amdgpu/vcn_v4_0_3.c b/drivers/gpu/drm/amd/amdgpu/vcn_v4_0_3.c index 712e1fba33ce..9729eb1fbc6c 100644 --- a/drivers/gpu/drm/amd/amdgpu/vcn_v4_0_3.c +++ b/drivers/gpu/drm/amd/amdgpu/vcn_v4_0_3.c @@ -970,6 +970,10 @@ static int vcn_v4_0_3_start_dpg_mode(struct amdgpu_vcn_inst *vinst, /*resetting done, fw can check RB ring */ fw_shared->sq.queue_mode &= cpu_to_le32(~FW_QUEUE_RING_RESET); + /* Keeping one read-back to ensure all register writes are done, otherwise + * it may introduce race conditions. + */ + RREG32_SOC15(VCN, vcn_inst, regVCN_RB_ENABLE); return 0; } -- 2.49.0
