V2: not to add extra read-back in vcn_v4_0_5_start as there is a
read-back already. New comment for better understanding.
On VCN v4.0.5 there is a race condition where the WPTR is not
updated after starting from idle when doorbell is used. The read-back
of regVCN_RB1_DB_CTRL register after written is to ensure the
doorbell_index is updated before it can work properly.
Closes: https://gitlab.freedesktop.org/mesa/mesa/-/issues/12528
Cc: sta...@vger.kernel.org
Signed-off-by: David (Ming Qiang) Wu <david....@amd.com>
Reviewed-by: Mario Limonciello <mario.limoncie...@amd.com>
Tested-by: Mario Limonciello <mario.limoncie...@amd.com>
---
drivers/gpu/drm/amd/amdgpu/vcn_v4_0_5.c | 4 ++++
1 file changed, 4 insertions(+)
diff --git a/drivers/gpu/drm/amd/amdgpu/vcn_v4_0_5.c
b/drivers/gpu/drm/amd/amdgpu/vcn_v4_0_5.c
index ed00d35039c13..e55b76d71367d 100644
--- a/drivers/gpu/drm/amd/amdgpu/vcn_v4_0_5.c
+++ b/drivers/gpu/drm/amd/amdgpu/vcn_v4_0_5.c
@@ -1034,6 +1034,10 @@ static int vcn_v4_0_5_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, regVCN_RB1_DB_CTRL);
+
return 0;
}
--
2.34.1
