Re: [PATCH v14 09/15] drm/panfrost: Warn of RPM get failure at device remove time

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [High] drm/panfrost: bus fault due to unpowered MMIO access in fini
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commit 1d33acca0e677034f1a99e084840bcc7a625c2cf
Author: Adrián Larumbe <adrian.larumbe@collabora.com>

drm/panfrost: Warn of RPM get failure at device remove time

This commit adds a warning during device removal if taking a PM reference 
fails. The goal is to avoid silent failures and notify the user when the 
PM resume operation is unsuccessful.

> diff --git a/drivers/gpu/drm/panfrost/panfrost_device.c b/drivers/gpu/drm/panfrost/panfrost_device.c
> index a6deabb39fd2c..6872302257431 100644
> --- a/drivers/gpu/drm/panfrost/panfrost_device.c
> +++ b/drivers/gpu/drm/panfrost/panfrost_device.c
[ ... ]
> @@ -385,7 +386,7 @@ int panfrost_device_init(struct panfrost_device *pfdev)
>  
>  void panfrost_device_fini(struct panfrost_device *pfdev)
>  {
> -	pm_runtime_get_sync(pfdev->base.dev);
> +	drm_WARN_ON(&pfdev->base, pm_runtime_get_sync(pfdev->base.dev) < 0);

[Severity: High]
If pm_runtime_get_sync() fails, it indicates the device is still in a
powered-off or clock-gated state. While this adds a warning, execution
continues unconditionally to the hardware teardown.

The teardown process then performs MMIO writes to an unpowered device. For
example, later in panfrost_device_fini(), these writes are executed:

panfrost_mmu_fini()
  mmu_write(pfdev, MMU_INT_MASK, 0);

panfrost_gpu_fini()
  panfrost_gpu_power_off()
    gpu_write(pfdev, SHADER_PWROFF_LO, pfdev->features.shader_present);

On ARM platforms, accessing MMIO of a powered-off device triggers a
synchronous external abort (bus fault), leading to a kernel panic. Should
this function return early or otherwise skip the hardware teardown steps if
the PM reference cannot be acquired?

>  
>  	pm_runtime_dont_use_autosuspend(pfdev->base.dev);
>  	pm_runtime_disable(pfdev->base.dev);

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Sashiko AI review · https://sashiko.dev/#/patchset/20261009-claude-fixes-v14-0-cb743b3b973b@collabora.com?part=9