From 4062119b9d958df33bcda703dc3ac646908fa861 Mon Sep 17 00:00:00 2001
From: Emily Deng <Emily.Deng@amd.com>
Date: Wed, 7 Mar 2018 09:47:43 +0800
Subject: [PATCH] drm/amdgpu: Clean sdma wptr register when only enable wptr
 polling
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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

Reviewed-by: Xiangliang Yu <Xiangliang.Yu@amd.com>
Reviewed-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Emily Deng <Emily.Deng@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@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 9c4efd4effc64..ecaef084dab14 100644
--- a/drivers/gpu/drm/amd/amdgpu/sdma_v3_0.c
+++ b/drivers/gpu/drm/amd/amdgpu/sdma_v3_0.c
@@ -711,14 +711,17 @@ 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 */
-- 
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