[PATCH] drm/amdgpu: Remove volatile from 'wb' & from 'ptr' in amdgpu.h

[Alex Deucher]

On Mon, Jul 24, 2023 at 11:54 AM Srinivasan Shanmugam
<srinivasan.shanmugam at amd.com> wrote:
>
> Fixes the following from checkpatch.pl:
>
> WARNING: Use of volatile is usually wrong: see Documentation/process/volatile-considered-harmful.rst
> +       volatile uint32_t       *wb;
>
> WARNING: Use of volatile is usually wrong: see Documentation/process/volatile-considered-harmful.rst
> +       volatile uint32_t               *ptr;
>
> 'wb' field from 'amdgpu_wb' struct & 'ptr' field from
> 'amdgpu_mem_scratch', is not used to access h/w directly, neither they
> are shared variables, so volatile is not necessary

How did you come to that determination?  Both are GPU accessible
memory allocations.  The writeback (wb) allocation happens to be in
GTT so it's system memory, but the the mem_scratch allocation can be
in device memory.

Alex

>
> Cc: Christian König <christian.koenig at amd.com>
> Cc: Alex Deucher <alexander.deucher at amd.com>
> Signed-off-by: Srinivasan Shanmugam <srinivasan.shanmugam at amd.com>
> ---
>  drivers/gpu/drm/amd/amdgpu/amdgpu.h | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu.h b/drivers/gpu/drm/amd/amdgpu/amdgpu.h
> index a046160b6a0e..06f79a84ff4b 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu.h
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu.h
> @@ -502,7 +502,7 @@ int amdgpu_file_to_fpriv(struct file *filp, struct amdgpu_fpriv **fpriv);
>
>  struct amdgpu_wb {
>         struct amdgpu_bo        *wb_obj;
> -       volatile uint32_t       *wb;
> +       u32                     *wb;
>         uint64_t                gpu_addr;
>         u32                     num_wb; /* Number of wb slots actually reserved for amdgpu. */
>         unsigned long           used[DIV_ROUND_UP(AMDGPU_MAX_WB, BITS_PER_LONG)];
> @@ -621,7 +621,7 @@ int amdgpu_cs_wait_fences_ioctl(struct drm_device *dev, void *data,
>  /* VRAM scratch page for HDP bug, default vram page */
>  struct amdgpu_mem_scratch {
>         struct amdgpu_bo                *robj;
> -       volatile uint32_t               *ptr;
> +       u32                             *ptr;
>         u64                             gpu_addr;
>  };
>
> --
> 2.25.1
>