drm/amdgpu/vcn:Add ring W/R PTR check for VCN DPG mode stop

Add ring write/read pointer check for VCN dynamic power gate mode
stop,to make sure that no job is left in ring before turn off DPG mode.

Signed-off-by: James Zhu <James.Zhu@amd.com>
Acked-by: Leo Liu <leo.liu@amd.com>
Acked-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/amdgpu/vcn_v1_0.c

@@ -1171,6 +1171,16 @@ static int vcn_v1_0_stop_dpg_mode(struct amdgpu_device *adev)
 			UVD_POWER_STATUS__UVD_POWER_STATUS_TILES_OFF,
 			UVD_POWER_STATUS__UVD_POWER_STATUS_MASK, ret_code);
 
+	if (ret_code) {
+		int tmp = RREG32_SOC15(UVD, 0, mmUVD_RBC_RB_WPTR) & 0x7FFFFFFF;
+		/* wait for read ptr to be equal to write ptr */
+		SOC15_WAIT_ON_RREG(UVD, 0, mmUVD_RBC_RB_RPTR, tmp, 0xFFFFFFFF, ret_code);
+
+		SOC15_WAIT_ON_RREG(UVD, 0, mmUVD_POWER_STATUS,
+			UVD_POWER_STATUS__UVD_POWER_STATUS_TILES_OFF,
+			UVD_POWER_STATUS__UVD_POWER_STATUS_MASK, ret_code);
+	}
+
 	/* disable dynamic power gating mode */
 	WREG32_P(SOC15_REG_OFFSET(UVD, 0, mmUVD_POWER_STATUS), 0,
 			~UVD_POWER_STATUS__UVD_PG_MODE_MASK);