Re: [PATCH v9 1/4] drm/panthor: Rework panthor_irq::suspended into panthor_irq::state

[Boris Brezillon <boris.brezillon@collabora.com>]

On Thu, 15 Jan 2026 14:58:59 +0100
Nicolas Frattaroli <nicolas.frattaroli@collabora.com> wrote:

> To deal with the threaded interrupt handler and a suspend action
> overlapping, the boolean panthor_irq::suspended is not sufficient.
> 
> Rework it into taking several different values depending on the current
> state, and check it and set it within the IRQ helper functions.
> 
> Signed-off-by: Nicolas Frattaroli <nicolas.frattaroli@collabora.com>
> ---
>  drivers/gpu/drm/panthor/panthor_device.h | 32 ++++++++++++++++++++++++++------
>  1 file changed, 26 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/gpu/drm/panthor/panthor_device.h b/drivers/gpu/drm/panthor/panthor_device.h
> index f35e52b9546a..2bf9a8434dc5 100644
> --- a/drivers/gpu/drm/panthor/panthor_device.h
> +++ b/drivers/gpu/drm/panthor/panthor_device.h
> @@ -61,6 +61,17 @@ enum panthor_device_pm_state {
>  	PANTHOR_DEVICE_PM_STATE_SUSPENDING,
>  };
>  
> +enum panthor_irq_state {
> +	/** @PANTHOR_IRQ_STATE_ACTIVE: IRQ is active and ready to process events. */
> +	PANTHOR_IRQ_STATE_ACTIVE = 0,
> +	/** @PANTHOR_IRQ_STATE_PROCESSING: IRQ is currently processing events. */
> +	PANTHOR_IRQ_STATE_PROCESSING,
> +	/** @PANTHOR_IRQ_STATE_SUSPENDED: IRQ is suspended. */
> +	PANTHOR_IRQ_STATE_SUSPENDED,
> +	/** @PANTHOR_IRQ_STATE_SUSPENDING: IRQ is being suspended. */
> +	PANTHOR_IRQ_STATE_SUSPENDING,
> +};
> +
>  /**
>   * struct panthor_irq - IRQ data
>   *
> @@ -76,8 +87,8 @@ struct panthor_irq {
>  	/** @mask: Current mask being applied to xxx_INT_MASK. */
>  	u32 mask;
>  
> -	/** @suspended: Set to true when the IRQ is suspended. */
> -	atomic_t suspended;
> +	/** @state: one of &enum panthor_irq_state reflecting the current state. */
> +	atomic_t state;
>  };
>  
>  /**
> @@ -409,8 +420,10 @@ static irqreturn_t panthor_ ## __name ## _irq_raw_handler(int irq, void *data)
>  {												\
>  	struct panthor_irq *pirq = data;							\
>  	struct panthor_device *ptdev = pirq->ptdev;						\
> +	enum panthor_irq_state state;								\
>  												\
> -	if (atomic_read(&pirq->suspended))							\
> +	state = atomic_read(&pirq->state);							\
> +	if (state == PANTHOR_IRQ_STATE_SUSPENDED || state == PANTHOR_IRQ_STATE_SUSPENDING)	\
>  		return IRQ_NONE;								\
>  	if (!gpu_read(ptdev, __reg_prefix ## _INT_STAT))					\
>  		return IRQ_NONE;								\

I was imagining something like:

	if (!gpu_read(ptdev, __reg_prefix ## _INT_STAT))
  		return IRQ_NONE;
	
	old_state = atomic_cmpxchg(&pirq->state,
				   PANTHOR_IRQ_STATE_ACTIVE,
				   PANTHOR_IRQ_STATE_PROCESSING);
	if (old_state != PANTHOR_IRQ_STATE_ACTIVE)
		return IRQ_NONE;

such that the processing phase starts as soon as we know we're going to
wake up the irq thread, not when we enter the threaded handler.

> @@ -423,8 +436,11 @@ static irqreturn_t panthor_ ## __name ## _irq_threaded_handler(int irq, void *da
>  {												\
>  	struct panthor_irq *pirq = data;							\
>  	struct panthor_device *ptdev = pirq->ptdev;						\
> +	enum panthor_irq_state state;								\
>  	irqreturn_t ret = IRQ_NONE;								\
>  												\
> +	atomic_cmpxchg(&pirq->state, PANTHOR_IRQ_STATE_ACTIVE, PANTHOR_IRQ_STATE_PROCESSING);	\

I think this is better done in the raw_handler (see above).

> +												\
>  	while (true) {										\
>  		u32 status = gpu_read(ptdev, __reg_prefix ## _INT_RAWSTAT) & pirq->mask;	\
>  												\
> @@ -435,8 +451,11 @@ static irqreturn_t panthor_ ## __name ## _irq_threaded_handler(int irq, void *da
>  		ret = IRQ_HANDLED;								\
>  	}											\
>  												\
> -	if (!atomic_read(&pirq->suspended))							\
> +	state = atomic_read(&pirq->state);							\
> +	if (state != PANTHOR_IRQ_STATE_SUSPENDED && state != PANTHOR_IRQ_STATE_SUSPENDING) {	\
>  		gpu_write(ptdev, __reg_prefix ## _INT_MASK, pirq->mask);			\
> +		atomic_set(&pirq->state, PANTHOR_IRQ_STATE_ACTIVE);				\
> +	}											\

Similarly, I think I'd go for

	old_state = atomic_cmpxchg(&pirq->state,
				   PANTHOR_IRQ_STATE_PROCESSING,
				   PANTHOR_IRQ_STATE_ACTIVE);
	if (old_state == PANTHOR_IRQ_STATE_PROCESSING)
  		gpu_write(ptdev, __reg_prefix ## _INT_MASK, pirq->mask);

>  												\
>  	return ret;										\
>  }												\
> @@ -445,14 +464,15 @@ static inline void panthor_ ## __name ## _irq_suspend(struct panthor_irq *pirq)
>  {												\
>  	pirq->mask = 0;										\
>  	gpu_write(pirq->ptdev, __reg_prefix ## _INT_MASK, 0);					\
> +	atomic_set(&pirq->state, PANTHOR_IRQ_STATE_SUSPENDING);					\
>  	synchronize_irq(pirq->irq);								\
> -	atomic_set(&pirq->suspended, true);							\
> +	atomic_set(&pirq->state, PANTHOR_IRQ_STATE_SUSPENDED);					\
>  }												\
>  												\
>  static inline void panthor_ ## __name ## _irq_resume(struct panthor_irq *pirq, u32 mask)	\
>  {												\
> -	atomic_set(&pirq->suspended, false);							\
>  	pirq->mask = mask;									\
> +	atomic_set(&pirq->state, PANTHOR_IRQ_STATE_ACTIVE);					\
>  	gpu_write(pirq->ptdev, __reg_prefix ## _INT_CLEAR, mask);				\
>  	gpu_write(pirq->ptdev, __reg_prefix ## _INT_MASK, mask);				\
>  }												\
>