From c3970cd97f7304414c12ca0c2362a34d0aac600a Mon Sep 17 00:00:00 2001 From: "David (Ming Qiang) Wu" Date: Wed, 14 May 2025 18:54:01 -0400 Subject: [PATCH] drm/amdgpu/vcn2.5: read back register after written [ Upstream commit d9e688b9148bb23629d32017344888dd67ec2ab1 ] The addition of register read-back in VCN v2.5 is intended to prevent potential race conditions. Reviewed-by: Ruijing Dong Signed-off-by: David (Ming Qiang) Wu Signed-off-by: Alex Deucher Signed-off-by: Sasha Levin --- drivers/gpu/drm/amd/amdgpu/vcn_v2_5.c | 19 +++++++++++++++++++ 1 file changed, 19 insertions(+) diff --git a/drivers/gpu/drm/amd/amdgpu/vcn_v2_5.c b/drivers/gpu/drm/amd/amdgpu/vcn_v2_5.c index 3eec1b8feaee..58b527a6b795 100644 --- a/drivers/gpu/drm/amd/amdgpu/vcn_v2_5.c +++ b/drivers/gpu/drm/amd/amdgpu/vcn_v2_5.c @@ -1158,6 +1158,11 @@ static int vcn_v2_5_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; } @@ -1343,6 +1348,11 @@ static int vcn_v2_5_start(struct amdgpu_vcn_inst *vinst) WREG32_SOC15(VCN, i, mmUVD_RB_SIZE2, ring->ring_size / 4); fw_shared->multi_queue.encode_lowlatency_queue_mode &= ~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; } @@ -1569,6 +1579,11 @@ static int vcn_v2_5_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; } @@ -1635,6 +1650,10 @@ static int vcn_v2_5_stop(struct amdgpu_vcn_inst *vinst) UVD_POWER_STATUS__UVD_POWER_STATUS_MASK, ~UVD_POWER_STATUS__UVD_POWER_STATUS_MASK); + /* 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);