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

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Use READ_ONCE() instead of declaring the pointer volatile. To prevent
the compiler from refetching or reordering the read, so that the read
value is always consistent.

Link: https://lwn.net/Articles/624126/
Cc: Felix Kuehling <Felix.Kuehling@amd.com>
Cc: Guchun Chen <guchun.chen@amd.com>
Cc: Christian König <christian.koenig@amd.com>
Cc: Alex Deucher <alexander.deucher@amd.com>
Cc: "Pan, Xinhui" <Xinhui.Pan@amd.com>
Cc: Le Ma <le.ma@amd.com>
Cc: Hawking Zhang <Hawking.Zhang@amd.com>
Signed-off-by: Srinivasan Shanmugam <srinivasan.shanmugam@amd.com>
Reviewed-by: Le Ma <le.ma@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
This commit is contained in:
Srinivasan Shanmugam 2023-08-04 11:16:41 +05:30 committed by Alex Deucher
parent 4d5dc6260c
commit bf227a4f05
1 changed files with 4 additions and 4 deletions
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8
drivers/gpu/drm/amd/amdgpu/sdma_v4_4_2.c
View file

@ -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;
}
/**