Commit bf227a4f authored by Srinivasan Shanmugam's avatar Srinivasan Shanmugam Committed by Alex Deucher
Browse files

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

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: default avatarSrinivasan Shanmugam <srinivasan.shanmugam@amd.com>
Reviewed-by: default avatarLe Ma <le.ma@amd.com>
Signed-off-by: default avatarAlex Deucher <alexander.deucher@amd.com>
parent 4d5dc626

drivers/gpu/drm/amd/amdgpu/sdma_v4_4_2.c

+4 −4
Original line number Diff line number Diff line
@@ -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;

}



/**