Re: [PATCH v3 3/3] drm/panthor: Take reqs_lock in soft_reset for clearing pending_reqs

[Boris Brezillon <boris.brezillon@collabora.com>]

On Tue, 11 Aug 2026 16:08:33 +0200
Nicolas Frattaroli <nicolas.frattaroli@collabora.com> wrote:

> panthor_gpu_soft_reset() sets pending_reqs to 0 without taking the
> requisite reqs_lock.
> 
> Fix this by taking the lock for the duration of the modification.
> 
> Fixes: 5cd894e258c4 ("drm/panthor: Add the GPU logical block")
> Signed-off-by: Nicolas Frattaroli <nicolas.frattaroli@collabora.com>
> ---
>  drivers/gpu/drm/panthor/panthor_gpu.c | 5 ++++-
>  1 file changed, 4 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/panthor/panthor_gpu.c b/drivers/gpu/drm/panthor/panthor_gpu.c
> index cb5319d1c5de..12e7e29b35b5 100644
> --- a/drivers/gpu/drm/panthor/panthor_gpu.c
> +++ b/drivers/gpu/drm/panthor/panthor_gpu.c
> @@ -405,7 +405,10 @@ int panthor_gpu_soft_reset(struct panthor_device *ptdev)
>  		return -ETIMEDOUT;
>  	}
>  
> -	ptdev->gpu->pending_reqs = 0;
> +	scoped_guard(spinlock, &ptdev->gpu->reqs_lock) {
> +		ptdev->gpu->pending_reqs = 0;
> +	}

In practice, this happens when nothing else interacts with the GPU
(IRQs have been suspended, and any access to the HW should be filtered
out/delayed until the reset is effective), but I agree it's safer and
more consistent to have this assigned done under the reqs_lock.

Reviewed-by: Boris Brezillon <boris.brezillon@collabora.com>