Re: [PATCH v5 04/12] drm/panfrost: Handle error when allocating AS number

[Steven Price <steven.price@arm.com>]

On 07/10/2025 16:01, Adrián Larumbe wrote:
> If we reach the beginning of the LRU AS list, then return an error.
> 
> Reviewed-by: Boris Brezillon <boris.brezillon@collabora.com>
> Signed-off-by: Adrián Larumbe <adrian.larumbe@collabora.com>

Very much "should never happen", but I guess adding error handling can't
hurt ;)

One minor NIT below, but either way:

Reviewed-by: Steven Price <steven.price@arm.com>

> ---
>  drivers/gpu/drm/panfrost/panfrost_job.c     | 6 +++++-
>  drivers/gpu/drm/panfrost/panfrost_mmu.c     | 5 +++--
>  drivers/gpu/drm/panfrost/panfrost_mmu.h     | 2 +-
>  drivers/gpu/drm/panfrost/panfrost_perfcnt.c | 9 ++++++++-
>  4 files changed, 17 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/gpu/drm/panfrost/panfrost_job.c b/drivers/gpu/drm/panfrost/panfrost_job.c
> index ea3f2878fd15..1b3af5d52081 100644
> --- a/drivers/gpu/drm/panfrost/panfrost_job.c
> +++ b/drivers/gpu/drm/panfrost/panfrost_job.c
> @@ -213,7 +213,11 @@ static int panfrost_job_hw_submit(struct panfrost_job *job, int js)
>  		goto err_hwsubmit;
>  	}
>  
> -	cfg = panfrost_mmu_as_get(pfdev, job->mmu);
> +	ret = panfrost_mmu_as_get(pfdev, job->mmu);
> +	if (ret < 0)
> +		goto err_hwsubmit;
> +
> +	cfg = ret;
>  
>  	panfrost_devfreq_record_busy(&pfdev->pfdevfreq);
>  
> diff --git a/drivers/gpu/drm/panfrost/panfrost_mmu.c b/drivers/gpu/drm/panfrost/panfrost_mmu.c
> index 1d696eeea2fa..cf272b167feb 100644
> --- a/drivers/gpu/drm/panfrost/panfrost_mmu.c
> +++ b/drivers/gpu/drm/panfrost/panfrost_mmu.c
> @@ -258,7 +258,7 @@ static int panfrost_mmu_cfg_init(struct panfrost_mmu *mmu,
>  	}
>  }
>  
> -u32 panfrost_mmu_as_get(struct panfrost_device *pfdev, struct panfrost_mmu *mmu)
> +int panfrost_mmu_as_get(struct panfrost_device *pfdev, struct panfrost_mmu *mmu)
>  {
>  	int as;
>  
> @@ -300,7 +300,8 @@ u32 panfrost_mmu_as_get(struct panfrost_device *pfdev, struct panfrost_mmu *mmu)
>  			if (!atomic_read(&lru_mmu->as_count))
>  				break;
>  		}
> -		WARN_ON(&lru_mmu->list == &pfdev->as_lru_list);
> +		if (WARN_ON(&lru_mmu->list == &pfdev->as_lru_list))
> +			return -EBUSY;
>  
>  		list_del_init(&lru_mmu->list);
>  		as = lru_mmu->as;
> diff --git a/drivers/gpu/drm/panfrost/panfrost_mmu.h b/drivers/gpu/drm/panfrost/panfrost_mmu.h
> index 022a9a74a114..e6e6966a0cca 100644
> --- a/drivers/gpu/drm/panfrost/panfrost_mmu.h
> +++ b/drivers/gpu/drm/panfrost/panfrost_mmu.h
> @@ -16,7 +16,7 @@ void panfrost_mmu_fini(struct panfrost_device *pfdev);
>  void panfrost_mmu_reset(struct panfrost_device *pfdev);
>  void panfrost_mmu_suspend_irq(struct panfrost_device *pfdev);
>  
> -u32 panfrost_mmu_as_get(struct panfrost_device *pfdev, struct panfrost_mmu *mmu);
> +int panfrost_mmu_as_get(struct panfrost_device *pfdev, struct panfrost_mmu *mmu);
>  void panfrost_mmu_as_put(struct panfrost_device *pfdev, struct panfrost_mmu *mmu);
>  
>  struct panfrost_mmu *panfrost_mmu_ctx_get(struct panfrost_mmu *mmu);
> diff --git a/drivers/gpu/drm/panfrost/panfrost_perfcnt.c b/drivers/gpu/drm/panfrost/panfrost_perfcnt.c
> index 718eb44b40f8..a8d821e1bde2 100644
> --- a/drivers/gpu/drm/panfrost/panfrost_perfcnt.c
> +++ b/drivers/gpu/drm/panfrost/panfrost_perfcnt.c
> @@ -132,7 +132,12 @@ static int panfrost_perfcnt_enable_locked(struct panfrost_device *pfdev,
>  
>  	perfcnt->user = user;

NIT: If we just move this line below the call to panfrost_mmu_as_get()
then we don't need the extra label and the special error handling.

Thanks,
Steve

>  
> -	as = panfrost_mmu_as_get(pfdev, perfcnt->mapping->mmu);
> +	ret = panfrost_mmu_as_get(pfdev, perfcnt->mapping->mmu);
> +	if (ret < 0)
> +		goto err_unsetuser;
> +
> +	as = ret;
> +
>  	cfg = GPU_PERFCNT_CFG_AS(as) |
>  	      GPU_PERFCNT_CFG_MODE(GPU_PERFCNT_CFG_MODE_MANUAL);
>  
> @@ -166,6 +171,8 @@ static int panfrost_perfcnt_enable_locked(struct panfrost_device *pfdev,
>  
>  	return 0;
>  
> +err_unsetuser:
> +	perfcnt->user = NULL;
>  err_vunmap:
>  	drm_gem_vunmap(&bo->base, &map);
>  err_put_mapping: