linux-kernel - Re: [PATCH v2 4/8] drm/panfrost: Handle error when allocating AS number

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Message-ID: <20241202102925.286fae57@collabora.com>
Date: Mon, 2 Dec 2024 10:29:25 +0100
From: Boris Brezillon <boris.brezillon@...labora.com>
To: Adrián Larumbe <adrian.larumbe@...labora.com>
Cc: Rob Herring <robh@...nel.org>, Steven Price <steven.price@....com>,
 Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>, Maxime Ripard
 <mripard@...nel.org>, Thomas Zimmermann <tzimmermann@...e.de>, David Airlie
 <airlied@...il.com>, Simona Vetter <simona@...ll.ch>, Philipp Zabel
 <p.zabel@...gutronix.de>, kernel@...labora.com,
 dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 4/8] drm/panfrost: Handle error when allocating AS
 number

On Thu, 28 Nov 2024 21:06:19 +0000
Adrián Larumbe <adrian.larumbe@...labora.com> wrote:

> If we reach the beginning of the LRU AS list, then return an error.
> 
> Signed-off-by: Adrián Larumbe <adrian.larumbe@...labora.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 3f4f0682d69d..fba1a376f593 100644
> --- a/drivers/gpu/drm/panfrost/panfrost_job.c
> +++ b/drivers/gpu/drm/panfrost/panfrost_job.c
> @@ -214,7 +214,11 @@ 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 = (u32)ret;
>  
>  	job_write(pfdev, JS_HEAD_NEXT_LO(js), lower_32_bits(jc_head));
>  	job_write(pfdev, JS_HEAD_NEXT_HI(js), upper_32_bits(jc_head));
> diff --git a/drivers/gpu/drm/panfrost/panfrost_mmu.c b/drivers/gpu/drm/panfrost/panfrost_mmu.c
> index 2189e42d2bfa..03ac527b35e7 100644
> --- a/drivers/gpu/drm/panfrost/panfrost_mmu.c
> +++ b/drivers/gpu/drm/panfrost/panfrost_mmu.c
> @@ -155,7 +155,7 @@ static void panfrost_mmu_disable(struct panfrost_device *pfdev, u32 as_nr)
>  	write_cmd(pfdev, as_nr, AS_COMMAND_UPDATE);
>  }
>  
> -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;
>  
> @@ -197,7 +197,8 @@ 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 f30817bcf8ba..2145f9707dde 100644
> --- a/drivers/gpu/drm/panfrost/panfrost_perfcnt.c
> +++ b/drivers/gpu/drm/panfrost/panfrost_perfcnt.c
> @@ -130,7 +130,12 @@ static int panfrost_perfcnt_enable_locked(struct panfrost_device *pfdev,
>  
>  	perfcnt->user = user;
>  
> -	as = panfrost_mmu_as_get(pfdev, perfcnt->mapping->mmu);
> +	ret = panfrost_mmu_as_get(pfdev, perfcnt->mapping->mmu);
> +	if (ret)
> +		goto err_unsetuser;
> +
> +	as = (u32)ret;

I don't think the explicit cast is needed, since you've already checked
that the result is positive.

Looks good otherwise.

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

> +
>  	cfg = GPU_PERFCNT_CFG_AS(as) |
>  	      GPU_PERFCNT_CFG_MODE(GPU_PERFCNT_CFG_MODE_MANUAL);
>  
> @@ -164,6 +169,8 @@ static int panfrost_perfcnt_enable_locked(struct panfrost_device *pfdev,
>  
>  	return 0;
>  
> +err_unsetuser:
> +	perfcnt->user = NULL;
>  err_vunmap:
>  	drm_gem_vunmap_unlocked(&bo->base, &map);
>  err_put_mapping: