From a8bce9b7a2ccb5cbbe9967a37e617a9ef963e540 Mon Sep 17 00:00:00 2001 From: "David (Ming Qiang) Wu" Date: Wed, 14 May 2025 18:58:37 -0400 Subject: [PATCH] drm/amdgpu/vcn5: read back register after written The addition of register read-back in VCN v5.0.0 is intended to prevent potential race conditions. Reviewed-by: Ruijing Dong Signed-off-by: David (Ming Qiang) Wu Signed-off-by: Alex Deucher --- drivers/gpu/drm/amd/amdgpu/vcn_v5_0_0.c | 20 ++++++++++++++++++++ 1 file changed, 20 insertions(+) diff --git a/drivers/gpu/drm/amd/amdgpu/vcn_v5_0_0.c b/drivers/gpu/drm/amd/amdgpu/vcn_v5_0_0.c index 27dcc6f37a73..f8e3f0b882da 100644 --- a/drivers/gpu/drm/amd/amdgpu/vcn_v5_0_0.c +++ b/drivers/gpu/drm/amd/amdgpu/vcn_v5_0_0.c @@ -794,6 +794,11 @@ static int vcn_v5_0_0_start_dpg_mode(struct amdgpu_vcn_inst *vinst, ring->doorbell_index << VCN_RB1_DB_CTRL__OFFSET__SHIFT | VCN_RB1_DB_CTRL__EN_MASK); + /* Keeping one read-back to ensure all register writes are done, + * otherwise it may introduce race conditions. + */ + RREG32_SOC15(VCN, inst_idx, regUVD_STATUS); + return 0; } @@ -946,6 +951,11 @@ static int vcn_v5_0_0_start(struct amdgpu_vcn_inst *vinst) WREG32_SOC15(VCN, i, 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, i, regUVD_STATUS); + return 0; } @@ -977,6 +987,11 @@ static void vcn_v5_0_0_stop_dpg_mode(struct amdgpu_vcn_inst *vinst) WREG32_P(SOC15_REG_OFFSET(VCN, inst_idx, regUVD_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, regUVD_STATUS); + return; } @@ -1058,6 +1073,11 @@ static int vcn_v5_0_0_stop(struct amdgpu_vcn_inst *vinst) /* enable VCN power gating */ vcn_v5_0_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, regUVD_STATUS); + done: if (adev->pm.dpm_enabled) amdgpu_dpm_enable_vcn(adev, false, i); -- 2.47.2