[PATCH 2/2] drm/panthor: Actually suspend IRQs in the unplug path

[Steven Price]

On 25/03/2024 10:41, Boris Brezillon wrote:
> panthor_xxx_irq_suspend() doesn't mask the interrupts if drm_dev_unplug()
> has been called, which is always the case when our panthor_xxx_unplug()
> helpers are called. Fix that by introducing a panthor_xxx_unplug() helper
> that does what panthor_xxx_irq_suspend() except it does it
> unconditionally.
> 
> Fixes: 5fe909cae118 ("drm/panthor: Add the device logical block")
> Signed-off-by: Boris Brezillon <boris.brezillon at collabora.com>
> ---
> Found inadvertently while debugging another issue. I guess I managed to
> call rmmod during a PING and that led to the FW interrupt handler
> being executed after the device suspend happened.
> ---
>  drivers/gpu/drm/panthor/panthor_device.h | 8 ++++++++
>  drivers/gpu/drm/panthor/panthor_fw.c     | 2 +-
>  drivers/gpu/drm/panthor/panthor_gpu.c    | 2 +-
>  drivers/gpu/drm/panthor/panthor_mmu.c    | 2 +-
>  4 files changed, 11 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/gpu/drm/panthor/panthor_device.h b/drivers/gpu/drm/panthor/panthor_device.h
> index 51c9d61b6796..ba43d5ea4e96 100644
> --- a/drivers/gpu/drm/panthor/panthor_device.h
> +++ b/drivers/gpu/drm/panthor/panthor_device.h
> @@ -321,6 +321,14 @@ static irqreturn_t panthor_ ## __name ## _irq_threaded_handler(int irq, void *da
>  	return ret;										\
>  }												\
>  												\
> +static inline void panthor_ ## __name ## _irq_unplug(struct panthor_irq *pirq)			\
> +{												\
> +	pirq->mask = 0;										\
> +	gpu_write(pirq->ptdev, __reg_prefix ## _INT_MASK, 0);					\
> +	synchronize_irq(pirq->irq);								\
> +	atomic_set(&pirq->suspended, true);							\
> +}												\
> +												\

This does things in a different order to _irq_suspend, is there a good
reason?
I'd expect:

{
	atomic_set(&pirq->suspended, true);
	gpu_write(pirq->ptdev, __reg_prefix ## _INT_MASK, 0);
	synchronize_irq(pirq->irq);
	pirq->mask = 0;
}

In particular I'm wondering if having the atomic_set after
synchronize_irq() could cause problems with an irq handler changing the
INT_MASK again (although AFAICT it should end up setting it to 0).

Otherwise this change looks good.

Thanks,

Steve

>  static inline void panthor_ ## __name ## _irq_suspend(struct panthor_irq *pirq)			\
>  {												\
>  	int cookie;										\
> diff --git a/drivers/gpu/drm/panthor/panthor_fw.c b/drivers/gpu/drm/panthor/panthor_fw.c
> index 33c87a59834e..7a9710a38c5f 100644
> --- a/drivers/gpu/drm/panthor/panthor_fw.c
> +++ b/drivers/gpu/drm/panthor/panthor_fw.c
> @@ -1128,7 +1128,7 @@ void panthor_fw_unplug(struct panthor_device *ptdev)
>  
>  	/* Make sure the IRQ handler can be called after that point. */
>  	if (ptdev->fw->irq.irq)
> -		panthor_job_irq_suspend(&ptdev->fw->irq);
> +		panthor_job_irq_unplug(&ptdev->fw->irq);
>  
>  	panthor_fw_stop(ptdev);
>  
> diff --git a/drivers/gpu/drm/panthor/panthor_gpu.c b/drivers/gpu/drm/panthor/panthor_gpu.c
> index 6dbbc4cfbe7e..b84c5b650fd9 100644
> --- a/drivers/gpu/drm/panthor/panthor_gpu.c
> +++ b/drivers/gpu/drm/panthor/panthor_gpu.c
> @@ -174,7 +174,7 @@ void panthor_gpu_unplug(struct panthor_device *ptdev)
>  	unsigned long flags;
>  
>  	/* Make sure the IRQ handler is not running after that point. */
> -	panthor_gpu_irq_suspend(&ptdev->gpu->irq);
> +	panthor_gpu_irq_unplug(&ptdev->gpu->irq);
>  
>  	/* Wake-up all waiters. */
>  	spin_lock_irqsave(&ptdev->gpu->reqs_lock, flags);
> diff --git a/drivers/gpu/drm/panthor/panthor_mmu.c b/drivers/gpu/drm/panthor/panthor_mmu.c
> index fdd35249169f..1f333cdded0f 100644
> --- a/drivers/gpu/drm/panthor/panthor_mmu.c
> +++ b/drivers/gpu/drm/panthor/panthor_mmu.c
> @@ -2622,7 +2622,7 @@ int panthor_vm_prepare_mapped_bos_resvs(struct drm_exec *exec, struct panthor_vm
>   */
>  void panthor_mmu_unplug(struct panthor_device *ptdev)
>  {
> -	panthor_mmu_irq_suspend(&ptdev->mmu->irq);
> +	panthor_mmu_irq_unplug(&ptdev->mmu->irq);
>  
>  	mutex_lock(&ptdev->mmu->as.slots_lock);
>  	for (u32 i = 0; i < ARRAY_SIZE(ptdev->mmu->as.slots); i++) {