[AMD Official Use Only - General]
Reviewed-by: Le Ma <le.ma@xxxxxxx>
> -----Original Message-----
> From: SHANMUGAM, SRINIVASAN <SRINIVASAN.SHANMUGAM@xxxxxxx>
> Sent: Friday, August 4, 2023 1:47 PM
> To: Koenig, Christian <Christian.Koenig@xxxxxxx>; Deucher, Alexander
> <Alexander.Deucher@xxxxxxx>; Chen, Guchun <Guchun.Chen@xxxxxxx>;
> Pan, Xinhui <Xinhui.Pan@xxxxxxx>
> Cc: amd-gfx@xxxxxxxxxxxxxxxxxxxxx; SHANMUGAM, SRINIVASAN
> <SRINIVASAN.SHANMUGAM@xxxxxxx>; Ma, Le <Le.Ma@xxxxxxx>; Zhang,
> Hawking <Hawking.Zhang@xxxxxxx>
> Subject: [PATCH] drm/amdgpu: Use READ_ONCE() when reading the values in
> 'sdma_v4_4_2_ring_get_rptr'
>
> 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.chen@xxxxxxx>
> Cc: Christian König <christian.koenig@xxxxxxx>
> Cc: Alex Deucher <alexander.deucher@xxxxxxx>
> Cc: "Pan, Xinhui" <Xinhui.Pan@xxxxxxx>
> Cc: Le Ma <le.ma@xxxxxxx>
> Cc: Hawking Zhang <Hawking.Zhang@xxxxxxx>
> Signed-off-by: Srinivasan Shanmugam <srinivasan.shanmugam@xxxxxxx>
> ---
> 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
