Re: [PATCH v5 06/11] drm/panfrost: Explicitly enable MMU interrupts at device init

[Boris Brezillon]

On Tue, 11 Aug 2026 22:42:15 +0100
Adrián Larumbe <adrian.larumbe@xxxxxxxxxxxxx> wrote:

> Because the device must be in a position to accept jobs between the time
> drm_dev_register() is called and autosuspend first kicks in, there's a very
> narrow window inbetween during which jobs targeting the tiler buffer
> object would time out, since the device's PM status is 'Active', but no MMU
> interrupts were enabled at device initialisation time.

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

It's probably good to have the IRQ regs initialized in the init()
function, though I'd like to be sure this is enough. If we assume
that a reset is what it takes to have a functional device, shouldn't we
do this reset in the device_init() path, before drm_dev_register() is
called?

> 
> Signed-off-by: Adrián Larumbe <adrian.larumbe@xxxxxxxxxxxxx>
> Fixes: 73e467f60acd ("drm/panfrost: Consolidate reset handling")
> ---
>  drivers/gpu/drm/panfrost/panfrost_mmu.c | 11 +++++++++--
>  1 file changed, 9 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/gpu/drm/panfrost/panfrost_mmu.c b/drivers/gpu/drm/panfrost/panfrost_mmu.c
> index 3fe37dd12360..a8ce5d65825c 100644
> --- a/drivers/gpu/drm/panfrost/panfrost_mmu.c
> +++ b/drivers/gpu/drm/panfrost/panfrost_mmu.c
> @@ -336,6 +336,12 @@ void panfrost_mmu_as_put(struct panfrost_device *pfdev, struct panfrost_mmu *mmu
>  	WARN_ON(atomic_read(&mmu->as_count) < 0);
>  }
>  
> +static void panfrost_mmu_enable_interrupts(struct panfrost_device *pfdev)
> +{
> +	mmu_write(pfdev, MMU_INT_CLEAR, ~0);
> +	mmu_write(pfdev, MMU_INT_MASK, ~0);
> +}
> +
>  void panfrost_mmu_reset(struct panfrost_device *pfdev)
>  {
>  	struct panfrost_mmu *mmu, *mmu_tmp;
> @@ -355,8 +361,7 @@ void panfrost_mmu_reset(struct panfrost_device *pfdev)
>  
>  	spin_unlock(&pfdev->as_lock);
>  
> -	mmu_write(pfdev, MMU_INT_CLEAR, ~0);
> -	mmu_write(pfdev, MMU_INT_MASK, ~0);
> +	panfrost_mmu_enable_interrupts(pfdev);
>  }
>  
>  static size_t get_pgsize(u64 addr, size_t size, size_t *count)
> @@ -970,6 +975,8 @@ int panfrost_mmu_init(struct panfrost_device *pfdev)
>  		return err;
>  	}
>  
> +	panfrost_mmu_enable_interrupts(pfdev);
> +
>  	return 0;
>  }
>  
>