[PATCH 01/10] drm/panthor: Make panthor_irq::state a non-atomic field

Boris Brezillon
2026-04-29T09:39:04Z

The only place where panthor_irq::state is accessed without
panthor_irq::mask_lock held is in the prologue of _irq_suspend(),
which is not really a fast-path. So let's simplify things by assuming
panthor_irq::state must always be accessed with the mask_lock held,
and add a scoped_guard() in _irq_suspend().

Signed-off-by: Boris Brezillon <boris.brezillon@collabora.com>
---
drivers/gpu/drm/panthor/panthor_device.h | 35 ++++++++++++++++----------------
1 file changed, 17 insertions(+), 18 deletions(-)

diff --git a/drivers/gpu/drm/panthor/panthor_device.h b/drivers/gpu/drm/panthor/panthor_device.h
index 4e4607bca7cc..3f91ba73829d 100644
--- a/drivers/gpu/drm/panthor/panthor_device.h
+++ b/drivers/gpu/drm/panthor/panthor_device.h
@@ -101,8 +101,12 @@ struct panthor_irq {
*/
spinlock_t mask_lock;

- /** @state: one of &enum panthor_irq_state reflecting the current state. */
- atomic_t state;
+ /**
+ * @state: one of &enum panthor_irq_state reflecting the current state.
+ *
+ * Must be accessed with mask_lock held.
+ */
+ enum panthor_irq_state state;
};

/**
@@ -510,18 +514,15 @@ const char *panthor_exception_name(struct panthor_device *ptdev,
static irqreturn_t panthor_ ## __name ## _irq_raw_handler(int irq, void *data) \
{ \
struct panthor_irq *pirq = data; \
- enum panthor_irq_state old_state; \
\
if (!gpu_read(pirq->iomem, INT_STAT)) \
return IRQ_NONE; \
\
guard(spinlock_irqsave)(&pirq->mask_lock); \
- old_state = atomic_cmpxchg(&pirq->state, \
- PANTHOR_IRQ_STATE_ACTIVE, \
- PANTHOR_IRQ_STATE_PROCESSING); \
- if (old_state != PANTHOR_IRQ_STATE_ACTIVE) \
+ if (pirq->state != PANTHOR_IRQ_STATE_ACTIVE) \
return IRQ_NONE; \
\
+ pirq->state = PANTHOR_IRQ_STATE_PROCESSING; \
gpu_write(pirq->iomem, INT_MASK, 0); \
return IRQ_WAKE_THREAD; \
} \
@@ -551,13 +552,10 @@ static irqreturn_t panthor_ ## __name ## _irq_threaded_handler(int irq, void *da
} \
\
scoped_guard(spinlock_irqsave, &pirq->mask_lock) { \
- enum panthor_irq_state old_state; \
- \
- old_state = atomic_cmpxchg(&pirq->state, \
- PANTHOR_IRQ_STATE_PROCESSING, \
- PANTHOR_IRQ_STATE_ACTIVE); \
- if (old_state == PANTHOR_IRQ_STATE_PROCESSING) \
+ if (pirq->state == PANTHOR_IRQ_STATE_PROCESSING) { \
+ pirq->state = PANTHOR_IRQ_STATE_ACTIVE; \
gpu_write(pirq->iomem, INT_MASK, pirq->mask); \
+ } \
} \
\
return ret; \
@@ -566,18 +564,19 @@ static irqreturn_t panthor_ ## __name ## _irq_threaded_handler(int irq, void *da
static inline void panthor_ ## __name ## _irq_suspend(struct panthor_irq *pirq) \
{ \
scoped_guard(spinlock_irqsave, &pirq->mask_lock) { \
- atomic_set(&pirq->state, PANTHOR_IRQ_STATE_SUSPENDING); \
+ pirq->state = PANTHOR_IRQ_STATE_SUSPENDING; \
gpu_write(pirq->iomem, INT_MASK, 0); \
} \
synchronize_irq(pirq->irq); \
- atomic_set(&pirq->state, PANTHOR_IRQ_STATE_SUSPENDED); \
+ scoped_guard(spinlock_irqsave, &pirq->mask_lock) \
+ 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->state, PANTHOR_IRQ_STATE_ACTIVE); \
+ pirq->state = PANTHOR_IRQ_STATE_ACTIVE; \
gpu_write(pirq->iomem, INT_CLEAR, pirq->mask); \
gpu_write(pirq->iomem, INT_MASK, pirq->mask); \
} \
@@ -610,7 +609,7 @@ static inline void panthor_ ## __name ## _irq_enable_events(struct panthor_irq *
* on the PROCESSING -> ACTIVE transition. \
* If the IRQ is suspended/suspending, the mask is restored at resume time. \
*/ \
- if (atomic_read(&pirq->state) == PANTHOR_IRQ_STATE_ACTIVE) \
+ if (pirq->state == PANTHOR_IRQ_STATE_ACTIVE) \
gpu_write(pirq->iomem, INT_MASK, pirq->mask); \
} \
\
@@ -624,7 +623,7 @@ static inline void panthor_ ## __name ## _irq_disable_events(struct panthor_irq
* on the PROCESSING -> ACTIVE transition. \
* If the IRQ is suspended/suspending, the mask is restored at resume time. \
*/ \
- if (atomic_read(&pirq->state) == PANTHOR_IRQ_STATE_ACTIVE) \
+ if (pirq->state == PANTHOR_IRQ_STATE_ACTIVE) \
gpu_write(pirq->iomem, INT_MASK, pirq->mask); \
}

--
2.53.0