From: Alex Deucher <alexander.deucher@amd.com>
Date: Thu, 27 Jul 2017 15:28:14 -0400
Subject: drm/amdgpu/sdma4: set wptr shadow atomically (v2)
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Git-commit: 575a07d2dabca6d05c3b59262fe754f9a52b29a6
Patch-mainline: v4.14-rc1
References: FATE#326289 FATE#326079 FATE#326049 FATE#322398 FATE#326166

No functional change until wptr polling uses this
location (future patch).

v2: use WRITE_ONCE

Cc: Frank Min <Frank.Min@amd.com>
Reviewed-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Acked-by: Petr Tesarik <ptesarik@suse.com>
---
 drivers/gpu/drm/amd/amdgpu/sdma_v4_0.c |    5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

--- a/drivers/gpu/drm/amd/amdgpu/sdma_v4_0.c
+++ b/drivers/gpu/drm/amd/amdgpu/sdma_v4_0.c
@@ -293,6 +293,8 @@ static void sdma_v4_0_ring_set_wptr(stru
 
 	DRM_DEBUG("Setting write pointer\n");
 	if (ring->use_doorbell) {
+		u64 *wb = (u64 *)&adev->wb.wb[ring->wptr_offs];
+
 		DRM_DEBUG("Using doorbell -- "
 				"wptr_offs == 0x%08x "
 				"lower_32_bits(ring->wptr) << 2 == 0x%08x "
@@ -301,8 +303,7 @@ static void sdma_v4_0_ring_set_wptr(stru
 				lower_32_bits(ring->wptr << 2),
 				upper_32_bits(ring->wptr << 2));
 		/* XXX check if swapping is necessary on BE */
-		adev->wb.wb[ring->wptr_offs] = lower_32_bits(ring->wptr << 2);
-		adev->wb.wb[ring->wptr_offs + 1] = upper_32_bits(ring->wptr << 2);
+		WRITE_ONCE(*wb, (ring->wptr << 2));
 		DRM_DEBUG("calling WDOORBELL64(0x%08x, 0x%016llx)\n",
 				ring->doorbell_index, ring->wptr << 2);