[PATCH v2] drm/amdgpu: Clean sdma wptr register when only enable wptr polling

[Emily Deng]

The sdma wptr polling memory is not fast enough, then the sdma
wptr register will be random, and not equal to sdma rptr, which
will cause sdma engine hang when load driver, so clean up the sdma
wptr directly to fix this issue.

v2:add comment above the code and correct coding style
Signed-off-by: Emily Deng <Emily.Deng at amd.com>
---
 drivers/gpu/drm/amd/amdgpu/sdma_v3_0.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/amd/amdgpu/sdma_v3_0.c b/drivers/gpu/drm/amd/amdgpu/sdma_v3_0.c
index 521978c..89ec17c 100644
--- a/drivers/gpu/drm/amd/amdgpu/sdma_v3_0.c
+++ b/drivers/gpu/drm/amd/amdgpu/sdma_v3_0.c
@@ -719,14 +719,17 @@ static int sdma_v3_0_gfx_resume(struct amdgpu_device *adev)
 		WREG32(mmSDMA0_GFX_RB_WPTR_POLL_ADDR_HI + sdma_offsets[i],
 		       upper_32_bits(wptr_gpu_addr));
 		wptr_poll_cntl = RREG32(mmSDMA0_GFX_RB_WPTR_POLL_CNTL + sdma_offsets[i]);
-		if (ring->use_pollmem)
+		if (ring->use_pollmem) {
+			/*wptr polling is not enogh fast, directly clean the wptr register */
+			WREG32(mmSDMA0_GFX_RB_WPTR + sdma_offsets[i], 0);
 			wptr_poll_cntl = REG_SET_FIELD(wptr_poll_cntl,
 						       SDMA0_GFX_RB_WPTR_POLL_CNTL,
 						       ENABLE, 1);
-		else
+		} else {
 			wptr_poll_cntl = REG_SET_FIELD(wptr_poll_cntl,
 						       SDMA0_GFX_RB_WPTR_POLL_CNTL,
 						       ENABLE, 0);
+		}
 		WREG32(mmSDMA0_GFX_RB_WPTR_POLL_CNTL + sdma_offsets[i], wptr_poll_cntl);
 
 		/* enable DMA RB */
-- 
2.7.4