Re: [PATCH v2 04/11] drm/panthor: Extend the IRQ logic to allow fast/hard IRQ handlers

[Chia-I Wu <olvaffe@gmail.com>]

On Tue, May 12, 2026 at 4:54 AM Boris Brezillon
<boris.brezillon@collabora.com> wrote:
>
> All drivers except panthor signal their fences from their interrupt
> handler to minimize latency. We could do the same from the threaded
> handler, but the latency is still quite high in that case, so let's
> allow components to choose the context they want their IRQ handler
> to run in by exposing support for custom hard handlers.
>
> Reviewed-by: Liviu Dudau <liviu.dudau@arm.com>
> Reviewed-by: Steven Price <steven.price@arm.com>
> Signed-off-by: Boris Brezillon <boris.brezillon@collabora.com>
> ---
>  drivers/gpu/drm/panthor/panthor_device.h | 11 ++++++++---
>  drivers/gpu/drm/panthor/panthor_fw.c     |  1 +
>  drivers/gpu/drm/panthor/panthor_gpu.c    |  1 +
>  drivers/gpu/drm/panthor/panthor_mmu.c    |  1 +
>  drivers/gpu/drm/panthor/panthor_pwr.c    |  1 +
>  5 files changed, 12 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/gpu/drm/panthor/panthor_device.h b/drivers/gpu/drm/panthor/panthor_device.h
> index 393fcda73d88..1aaf06df875b 100644
> --- a/drivers/gpu/drm/panthor/panthor_device.h
> +++ b/drivers/gpu/drm/panthor/panthor_device.h
> @@ -672,6 +672,7 @@ static inline void panthor_irq_disable_events(struct panthor_irq *pirq, u32 mask
>  static inline int
>  panthor_irq_request(struct panthor_device *ptdev, struct panthor_irq *pirq,
>                     int irq, u32 mask, void __iomem *iomem, const char *name,
> +                   irqreturn_t (*raw_handler)(int, void *data),
>                     irqreturn_t (*threaded_handler)(int, void *data))
>  {
>         const char *full_name;
> @@ -687,9 +688,13 @@ panthor_irq_request(struct panthor_device *ptdev, struct panthor_irq *pirq,
>                 return -ENOMEM;
>
>         panthor_irq_resume(pirq);
> -       return devm_request_threaded_irq(ptdev->base.dev, irq,
> -                                        panthor_irq_default_raw_handler,
> -                                        threaded_handler,
> +
> +       if (!threaded_handler) {
> +               return devm_request_irq(ptdev->base.dev, irq, raw_handler,
> +                                       IRQF_SHARED, full_name, pirq);
> +       }
devm_request_irq expands to devm_request_threaded_irq plus
IRQF_COND_ONESHOT. This appears redundant.

> +
> +       return devm_request_threaded_irq(ptdev->base.dev, irq, raw_handler, threaded_handler,
>                                          IRQF_SHARED, full_name, pirq);
>  }
>
> diff --git a/drivers/gpu/drm/panthor/panthor_fw.c b/drivers/gpu/drm/panthor/panthor_fw.c
> index eaf599b0a887..8239a6951569 100644
> --- a/drivers/gpu/drm/panthor/panthor_fw.c
> +++ b/drivers/gpu/drm/panthor/panthor_fw.c
> @@ -1483,6 +1483,7 @@ int panthor_fw_init(struct panthor_device *ptdev)
>
>         ret = panthor_irq_request(ptdev, &fw->irq, irq, 0,
>                                   ptdev->iomem + JOB_INT_BASE, "job",
> +                                 panthor_irq_default_raw_handler,
>                                   panthor_job_irq_threaded_handler);
>         if (ret) {
>                 drm_err(&ptdev->base, "failed to request job irq");
> diff --git a/drivers/gpu/drm/panthor/panthor_gpu.c b/drivers/gpu/drm/panthor/panthor_gpu.c
> index ce208e384762..d0be758ea3e1 100644
> --- a/drivers/gpu/drm/panthor/panthor_gpu.c
> +++ b/drivers/gpu/drm/panthor/panthor_gpu.c
> @@ -177,6 +177,7 @@ int panthor_gpu_init(struct panthor_device *ptdev)
>         ret = panthor_irq_request(ptdev, &ptdev->gpu->irq, irq,
>                                   GPU_INTERRUPTS_MASK,
>                                   ptdev->iomem + GPU_INT_BASE, "gpu",
> +                                 panthor_irq_default_raw_handler,
>                                   panthor_gpu_irq_threaded_handler);
>         if (ret)
>                 return ret;
> diff --git a/drivers/gpu/drm/panthor/panthor_mmu.c b/drivers/gpu/drm/panthor/panthor_mmu.c
> index 375022fb3fd8..2955b8baa2e2 100644
> --- a/drivers/gpu/drm/panthor/panthor_mmu.c
> +++ b/drivers/gpu/drm/panthor/panthor_mmu.c
> @@ -3266,6 +3266,7 @@ int panthor_mmu_init(struct panthor_device *ptdev)
>         ret = panthor_irq_request(ptdev, &mmu->irq, irq,
>                                   panthor_mmu_fault_mask(ptdev, ~0),
>                                   ptdev->iomem + MMU_INT_BASE, "mmu",
> +                                 panthor_irq_default_raw_handler,
>                                   panthor_mmu_irq_threaded_handler);
>         if (ret)
>                 return ret;
> diff --git a/drivers/gpu/drm/panthor/panthor_pwr.c b/drivers/gpu/drm/panthor/panthor_pwr.c
> index 80cf78007896..1efb7f3482ba 100644
> --- a/drivers/gpu/drm/panthor/panthor_pwr.c
> +++ b/drivers/gpu/drm/panthor/panthor_pwr.c
> @@ -491,6 +491,7 @@ int panthor_pwr_init(struct panthor_device *ptdev)
>         err = panthor_irq_request(
>                 ptdev, &pwr->irq, irq, PWR_INTERRUPTS_MASK,
>                 pwr->iomem + PWR_INT_BASE, "pwr",
> +               panthor_irq_default_raw_handler,
>                 panthor_pwr_irq_threaded_handler);
>         if (err)
>                 return err;
>
> --
> 2.54.0
>