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Message-ID: <5069507.31r3eYUQgx@workhorse>
Date: Mon, 12 Jan 2026 14:39:25 +0100
From: Nicolas Frattaroli <nicolas.frattaroli@...labora.com>
To: Boris Brezillon <boris.brezillon@...labora.com>,
Liviu Dudau <liviu.dudau@....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>,
Chia-I Wu <olvaffe@...il.com>, Karunika Choo <karunika.choo@....com>,
Steven Price <steven.price@....com>
Cc: kernel@...labora.com, linux-kernel@...r.kernel.org,
dri-devel@...ts.freedesktop.org
Subject:
Re: [PATCH v7 2/4] drm/panthor: Rework panthor_irq::suspended into
panthor_irq::state
On Friday, 9 January 2026 17:05:05 Central European Standard Time Steven Price wrote:
> On 08/01/2026 14:19, Nicolas Frattaroli 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@...labora.com>
> > ---
> > drivers/gpu/drm/panthor/panthor_device.h | 40 +++++++++++++++++++++++++-------
> > 1 file changed, 32 insertions(+), 8 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/panthor/panthor_device.h b/drivers/gpu/drm/panthor/panthor_device.h
> > index cf76a8abca76..a8c21a7eea05 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: Values to write to xxx_INT_MASK if active. */
> > 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;
> >
> > /** @mask_lock: protects modifications to _INT_MASK and @mask */
> > spinlock_t mask_lock;
> > @@ -415,7 +426,7 @@ static irqreturn_t panthor_ ## __name ## _irq_raw_handler(int irq, void *data)
> > \
> > guard(spinlock_irqsave)(&pirq->mask_lock); \
> > \
> > - if (atomic_read(&pirq->suspended)) \
> > + if (atomic_read(&pirq->state) == PANTHOR_IRQ_STATE_SUSPENDED) \
>
> Do we want to also catch the STATE_SUSPENDING case here? AFAICT in
> SUSPENDING we should be confident that _INT_MASK==0 so this shouldn't a
> problem (_INT_STAT should read as 0 below). But we don't want interrupts
> during STATE_SUSPENDING so we might as well handle it.
Depends on what we want to happen here, I think. If the suspend handler
writing 0 to _INT_MASK does not also happen to clear _INT_STAT, then as
far as I can see, we may enter _irq_raw_handler, block for the lock as
suspend drops it, and then enter the function with STATE_SUSPENDING in
a context where we'd probably want to process the remaining interrupts
(i.e. suspend is at synchronise_irq() or about to be there, and we're
handling the last IRQ that got raised before mask was written to 0).
Let me know if my understanding here is correct, because I think in such
a case, it's reasonable to process that last IRQ instead of discarding it,
unless that's something frowned upon that I'm not aware of.
>
> Thanks,
> Steve
>
> > return IRQ_NONE; \
> > if (!gpu_read(ptdev, __reg_prefix ## _INT_STAT)) \
> > return IRQ_NONE; \
> > @@ -428,11 +439,14 @@ 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; \
> > u32 mask; \
> > \
> > scoped_guard(spinlock_irqsave, &pirq->mask_lock) { \
> > mask = pirq->mask; \
> > + atomic_cmpxchg(&pirq->state, PANTHOR_IRQ_STATE_ACTIVE, \
> > + PANTHOR_IRQ_STATE_PROCESSING); \
> > } \
> > \
> > while (true) { \
> > @@ -446,11 +460,14 @@ static irqreturn_t panthor_ ## __name ## _irq_threaded_handler(int irq, void *da
> > } \
> > \
> > scoped_guard(spinlock_irqsave, &pirq->mask_lock) { \
> > - if (!atomic_read(&pirq->suspended)) { \
> > + state = atomic_read(&pirq->state); \
> > + if (state != PANTHOR_IRQ_STATE_SUSPENDED && \
> > + state != PANTHOR_IRQ_STATE_SUSPENDING) { \
> > /* Only restore the bits that were used and are still enabled */ \
> > gpu_write(ptdev, __reg_prefix ## _INT_MASK, \
> > gpu_read(ptdev, __reg_prefix ## _INT_MASK) | \
> > (mask & pirq->mask)); \
> > + atomic_set(&pirq->state, PANTHOR_IRQ_STATE_ACTIVE); \
> > } \
> > } \
> > \
> > @@ -461,16 +478,17 @@ static inline void panthor_ ## __name ## _irq_suspend(struct panthor_irq *pirq)
> > { \
> > scoped_guard(spinlock_irqsave, &pirq->mask_lock) { \
> > 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) \
> > { \
> > guard(spinlock_irqsave)(&pirq->mask_lock); \
> > \
> > - atomic_set(&pirq->suspended, false); \
> > + atomic_set(&pirq->state, PANTHOR_IRQ_STATE_ACTIVE); \
> > gpu_write(pirq->ptdev, __reg_prefix ## _INT_CLEAR, pirq->mask); \
> > gpu_write(pirq->ptdev, __reg_prefix ## _INT_MASK, pirq->mask); \
> > } \
> > @@ -494,19 +512,25 @@ static int panthor_request_ ## __name ## _irq(struct panthor_device *ptdev, \
> > \
> > static inline void panthor_ ## __name ## _irq_enable_events(struct panthor_irq *pirq, u32 mask) \
> > { \
> > + enum panthor_irq_state state; \
> > + \
> > guard(spinlock_irqsave)(&pirq->mask_lock); \
> > \
> > pirq->mask |= mask; \
> > - if (!atomic_read(&pirq->suspended)) \
> > + state = atomic_read(&pirq->state); \
> > + if (state != PANTHOR_IRQ_STATE_SUSPENDED && state != PANTHOR_IRQ_STATE_SUSPENDING) \
> > gpu_write(pirq->ptdev, __reg_prefix ## _INT_MASK, pirq->mask); \
> > } \
> > \
> > static inline void panthor_ ## __name ## _irq_disable_events(struct panthor_irq *pirq, u32 mask)\
> > { \
> > + enum panthor_irq_state state; \
> > + \
> > guard(spinlock_irqsave)(&pirq->mask_lock); \
> > \
> > pirq->mask &= ~mask; \
> > - if (!atomic_read(&pirq->suspended)) \
> > + state = atomic_read(&pirq->state); \
> > + if (state != PANTHOR_IRQ_STATE_SUSPENDED && state != PANTHOR_IRQ_STATE_SUSPENDING) \
> > gpu_write(pirq->ptdev, __reg_prefix ## _INT_MASK, pirq->mask); \
> > }
> >
> >
>
>
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