Re: [PATCH] drm/amdgpu: use bitmap_clear() in amdgpu_amdkfd_device_init()

[Yury Norov <ynorov@nvidia.com>]

On Thu, Apr 23, 2026 at 08:52:17PM -0400, Yury Norov wrote:
> The bitmap_clear() works OK with both compile- and runtime nbits. But the
> comment says it doesn't work, and opencodes the call for nothing. Drop
> the misleading comment, and use bitmap_clear() as it should.
> 
> As a side effect, the patch switches from a series of atomics to
> a single non-atomic operation, which is easier on caches.
> 
> Signed-off-by: Yury Norov <ynorov@nvidia.com>
> ---
>  drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd.c | 7 ++-----
>  1 file changed, 2 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd.c
> index d9e283f3b57d..47d52cb2f1ba 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd.c
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd.c
> @@ -194,14 +194,11 @@ void amdgpu_amdkfd_device_init(struct amdgpu_device *adev)
>  				  adev->gfx.mec_bitmap[0].queue_bitmap,
>  				  AMDGPU_MAX_QUEUES);
>  
> -		/* According to linux/bitmap.h we shouldn't use bitmap_clear if
> -		 * nbits is not compile time constant
> -		 */
>  		last_valid_bit = 1 /* only first MEC can have compute queues */
>  				* adev->gfx.mec.num_pipe_per_mec
>  				* adev->gfx.mec.num_queue_per_pipe;
> -		for (i = last_valid_bit; i < AMDGPU_MAX_QUEUES; ++i)
> -			clear_bit(i, gpu_resources.cp_queue_bitmap);

Please disregard. This patch accidentally dropped a chunk removing 'i'
declaration. I'll resend shortly.

> +		bitmap_clear(gpu_resources.cp_queue_bitmap, last_valid_bit,
> +					AMDGPU_MAX_QUEUES - last_valid_bit);
>  
>  		amdgpu_doorbell_get_kfd_info(adev,
>  				&gpu_resources.doorbell_physical_address,
> -- 
> 2.51.0
>