From: "Xiangliang.Yu" <Xiangliang.Yu@amd.com>
Date: Wed, 13 Sep 2017 10:58:19 +0800
Subject: drm/amdgpu/sdma3: set wptr shadow atomically
Git-commit: 3e4b0bd96092bbf9c5a538916a61faa5eca8e9cb
Patch-mainline: v4.15-rc1
References: FATE#326289 FATE#326079 FATE#326049 FATE#322398 FATE#326166

Port it from sdma4 for wptr polling usage.

Signed-off-by: Xiangliang.Yu <Xiangliang.Yu@amd.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Acked-by: Petr Tesarik <ptesarik@suse.com>
---
 drivers/gpu/drm/amd/amdgpu/sdma_v3_0.c |    4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

--- a/drivers/gpu/drm/amd/amdgpu/sdma_v3_0.c
+++ b/drivers/gpu/drm/amd/amdgpu/sdma_v3_0.c
@@ -379,8 +379,10 @@ static void sdma_v3_0_ring_set_wptr(stru
 	struct amdgpu_device *adev = ring->adev;
 
 	if (ring->use_doorbell) {
+		u32 *wb = (u32 *)&adev->wb.wb[ring->wptr_offs];
+
 		/* XXX check if swapping is necessary on BE */
-		adev->wb.wb[ring->wptr_offs] = lower_32_bits(ring->wptr) << 2;
+		WRITE_ONCE(*wb, (lower_32_bits(ring->wptr) << 2));
 		WDOORBELL32(ring->doorbell_index, lower_32_bits(ring->wptr) << 2);
 	} else {
 		int me = (ring == &ring->adev->sdma.instance[0].ring) ? 0 : 1;