From: Chia-I Wu <olvaffe@gmail.com>
To: Boris Brezillon <boris.brezillon@collabora.com>
Cc: Steven Price <steven.price@arm.com>,
Liviu Dudau <liviu.dudau@arm.com>,
Maarten Lankhorst <maarten.lankhorst@linux.intel.com>,
Maxime Ripard <mripard@kernel.org>,
Thomas Zimmermann <tzimmermann@suse.de>,
David Airlie <airlied@gmail.com>, Simona Vetter <simona@ffwll.ch>,
dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH v2 01/11] drm/panthor: Make panthor_irq::state a non-atomic field
Date: Tue, 12 May 2026 11:40:22 -0700 [thread overview]
Message-ID: <CAPaKu7SUFiJ0O_v0yM2rrusUgzOUZ1Jb=Dm=ejFBPn8Sc6MYug@mail.gmail.com> (raw)
In-Reply-To: <20260512-panthor-signal-from-irq-v2-1-95c614a739cb@collabora.com>
On Tue, May 12, 2026 at 4:44 AM Boris Brezillon
<boris.brezillon@collabora.com> wrote:
>
> 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().
>
> Reviewed-by: Steven Price <steven.price@arm.com>
> Reviewed-by: Liviu Dudau <liviu.dudau@arm.com>
> Signed-off-by: Boris Brezillon <boris.brezillon@collabora.com>
Reviewed-by: Chia-I Wu <olvaffe@gmail.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;
optional nit: might want to rename 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); \
> }
>
>
> --
> 2.54.0
>
next prev parent reply other threads:[~2026-05-12 18:40 UTC|newest]
Thread overview: 53+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-05-12 11:37 [PATCH v2 00/11] drm/panthor: Reduce dma_fence signalling latency Boris Brezillon
2026-05-12 11:37 ` [PATCH v2 01/11] drm/panthor: Make panthor_irq::state a non-atomic field Boris Brezillon
2026-05-12 18:40 ` Chia-I Wu [this message]
2026-05-16 3:32 ` Claude review: " Claude Code Review Bot
2026-05-12 11:37 ` [PATCH v2 02/11] drm/panthor: Move the register accessors before the IRQ helpers Boris Brezillon
2026-05-12 18:41 ` Chia-I Wu
2026-05-16 3:32 ` Claude review: " Claude Code Review Bot
2026-05-12 11:37 ` [PATCH v2 03/11] drm/panthor: Replace the panthor_irq macro machinery by inline helpers Boris Brezillon
2026-05-12 18:58 ` Chia-I Wu
2026-05-13 8:03 ` Boris Brezillon
2026-05-13 16:46 ` Chia-I Wu
2026-05-16 3:32 ` Claude review: " Claude Code Review Bot
2026-05-12 11:37 ` [PATCH v2 04/11] drm/panthor: Extend the IRQ logic to allow fast/hard IRQ handlers Boris Brezillon
2026-05-12 19:11 ` Chia-I Wu
2026-05-13 8:09 ` Boris Brezillon
2026-05-13 17:06 ` Chia-I Wu
2026-05-13 17:30 ` Boris Brezillon
2026-05-13 18:17 ` Chia-I Wu
2026-05-16 3:32 ` Claude review: " Claude Code Review Bot
2026-05-12 11:37 ` [PATCH v2 05/11] drm/panthor: Make panthor_fw_{update,toggle}_reqs() callable from IRQ context Boris Brezillon
2026-05-12 19:29 ` [PATCH v2 05/11] drm/panthor: Make panthor_fw_{update, toggle}_reqs() " Chia-I Wu
2026-05-16 3:32 ` Claude review: drm/panthor: Make panthor_fw_{update,toggle}_reqs() " Claude Code Review Bot
2026-05-12 11:37 ` [PATCH v2 06/11] drm/panthor: Prepare the scheduler logic for FW events in " Boris Brezillon
2026-05-12 21:04 ` Chia-I Wu
2026-05-13 8:29 ` Boris Brezillon
2026-05-13 17:47 ` Chia-I Wu
2026-05-16 3:32 ` Claude review: " Claude Code Review Bot
2026-05-12 11:37 ` [PATCH v2 07/11] drm/panthor: Automate CSG IRQ processing at group unbind time Boris Brezillon
2026-05-12 21:16 ` Chia-I Wu
2026-05-14 14:17 ` Steven Price
2026-05-16 3:32 ` Claude review: " Claude Code Review Bot
2026-05-12 11:37 ` [PATCH v2 08/11] drm/panthor: Automatically enable interrupts in panthor_fw_wait_acks() Boris Brezillon
2026-05-12 21:55 ` Chia-I Wu
2026-05-13 8:42 ` Boris Brezillon
2026-05-13 17:14 ` Chia-I Wu
2026-05-14 14:25 ` Steven Price
2026-05-16 3:32 ` Claude review: " Claude Code Review Bot
2026-05-12 11:37 ` [PATCH v2 09/11] drm/panthor: Process FW events in IRQ context Boris Brezillon
2026-05-12 22:05 ` Chia-I Wu
2026-05-12 22:09 ` Chia-I Wu
2026-05-13 8:44 ` Boris Brezillon
2026-05-14 15:23 ` Steven Price
2026-05-16 3:32 ` Claude review: " Claude Code Review Bot
2026-05-12 11:37 ` [PATCH v2 10/11] drm/panthor: Use the irqsave variant of spin_lock in panthor_gpu_irq_handler() Boris Brezillon
2026-05-14 15:26 ` Steven Price
2026-05-16 3:32 ` Claude review: " Claude Code Review Bot
2026-05-12 11:37 ` [PATCH v2 11/11] drm/panthor: Process GPU events in IRQ context Boris Brezillon
2026-05-12 11:50 ` Boris Brezillon
2026-05-12 22:40 ` Chia-I Wu
2026-05-13 8:54 ` Boris Brezillon
2026-05-13 18:07 ` Chia-I Wu
2026-05-16 3:32 ` Claude review: " Claude Code Review Bot
2026-05-16 3:32 ` Claude review: drm/panthor: Reduce dma_fence signalling latency Claude Code Review Bot
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