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

Yury Norov
2026-04-24T01:27:27Z

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
>