The addition of register read-back in VCN v3.0 is intended to prevent potential race conditions.
Signed-off-by: David (Ming Qiang) Wu <[email protected]> --- drivers/gpu/drm/amd/amdgpu/vcn_v3_0.c | 20 ++++++++++++++++++++ 1 file changed, 20 insertions(+) diff --git a/drivers/gpu/drm/amd/amdgpu/vcn_v3_0.c b/drivers/gpu/drm/amd/amdgpu/vcn_v3_0.c index 0b19f0ab4480d..9fb0d53805892 100644 --- a/drivers/gpu/drm/amd/amdgpu/vcn_v3_0.c +++ b/drivers/gpu/drm/amd/amdgpu/vcn_v3_0.c @@ -1173,6 +1173,11 @@ static int vcn_v3_0_start_dpg_mode(struct amdgpu_vcn_inst *vinst, bool indirect) WREG32_P(SOC15_REG_OFFSET(VCN, inst_idx, mmUVD_POWER_STATUS), 0, ~UVD_POWER_STATUS__STALL_DPG_POWER_UP_MASK); + /* Keeping one read-back to ensure all register writes are done, + * otherwise it may introduce race conditions. + */ + RREG32_SOC15(VCN, inst_idx, mmUVD_STATUS); + return 0; } @@ -1360,6 +1365,11 @@ static int vcn_v3_0_start(struct amdgpu_vcn_inst *vinst) fw_shared->multi_queue.encode_lowlatency_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, i, mmUVD_STATUS); + return 0; } @@ -1602,6 +1612,11 @@ static int vcn_v3_0_stop_dpg_mode(struct amdgpu_vcn_inst *vinst) WREG32_P(SOC15_REG_OFFSET(VCN, inst_idx, mmUVD_POWER_STATUS), 0, ~UVD_POWER_STATUS__UVD_PG_MODE_MASK); + /* Keeping one read-back to ensure all register writes are done, + * otherwise it may introduce race conditions. + */ + RREG32_SOC15(VCN, inst_idx, mmUVD_STATUS); + return 0; } @@ -1674,6 +1689,11 @@ static int vcn_v3_0_stop(struct amdgpu_vcn_inst *vinst) /* enable VCN power gating */ vcn_v3_0_enable_static_power_gating(vinst); + /* Keeping one read-back to ensure all register writes are done, + * otherwise it may introduce race conditions. + */ + RREG32_SOC15(VCN, i, mmUVD_STATUS); + done: if (adev->pm.dpm_enabled) amdgpu_dpm_enable_vcn(adev, false, i); -- 2.34.1
