[PATCH] drm/amdgpu: Use READ_ONCE() when reading the values in 'sdma_v4_4_2_ring_get_rptr'

[Srinivasan Shanmugam]

Instead of declaring pointers use READ_ONCE(), when accessing those
values to make sure that the compiler doesn't voilate any cache
coherences

Cc: Guchun Chen <guchun.c...@amd.com>
Cc: Christian König <christian.koe...@amd.com>
Cc: Alex Deucher <alexander.deuc...@amd.com>
Cc: "Pan, Xinhui" <xinhui....@amd.com>
Cc: Le Ma <le...@amd.com>
Cc: Hawking Zhang <hawking.zh...@amd.com>
Signed-off-by: Srinivasan Shanmugam <srinivasan.shanmu...@amd.com>
---
 drivers/gpu/drm/amd/amdgpu/sdma_v4_4_2.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/drivers/gpu/drm/amd/amdgpu/sdma_v4_4_2.c 
b/drivers/gpu/drm/amd/amdgpu/sdma_v4_4_2.c
index f413898dda37..267c1b7b8dcd 100644
--- a/drivers/gpu/drm/amd/amdgpu/sdma_v4_4_2.c
+++ b/drivers/gpu/drm/amd/amdgpu/sdma_v4_4_2.c
@@ -154,13 +154,13 @@ static int sdma_v4_4_2_init_microcode(struct 
amdgpu_device *adev)
  */
 static uint64_t sdma_v4_4_2_ring_get_rptr(struct amdgpu_ring *ring)
 {
-       u64 *rptr;
+       u64 rptr;
 
        /* XXX check if swapping is necessary on BE */
-       rptr = ((u64 *)&ring->adev->wb.wb[ring->rptr_offs]);
+       rptr = READ_ONCE(*((u64 *)&ring->adev->wb.wb[ring->rptr_offs]));
 
-       DRM_DEBUG("rptr before shift == 0x%016llx\n", *rptr);
-       return ((*rptr) >> 2);
+       DRM_DEBUG("rptr before shift == 0x%016llx\n", rptr);
+       return rptr >> 2;
 }
 
 /**
-- 
2.25.1