Re: [PATCH v2 09/11] drm/panthor: Process FW events in IRQ context

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

On Tue, May 12, 2026 at 3:05 PM Chia-I Wu <olvaffe@gmail.com> wrote:
>
> On Tue, May 12, 2026 at 4:54 AM Boris Brezillon
> <boris.brezillon@collabora.com> wrote:
> >
> > Now that everything is set to allow processing FW events in IRQ context,
> > go for it. This should reduce the dma_fence signaling latency.
> >
> > Signed-off-by: Boris Brezillon <boris.brezillon@collabora.com>
> > ---
> >  drivers/gpu/drm/panthor/panthor_fw.c | 27 +++++++++++++++++++++++----
> >  1 file changed, 23 insertions(+), 4 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/panthor/panthor_fw.c b/drivers/gpu/drm/panthor/panthor_fw.c
> > index f5e0ceca4130..8cfebf180de7 100644
> > --- a/drivers/gpu/drm/panthor/panthor_fw.c
> > +++ b/drivers/gpu/drm/panthor/panthor_fw.c
> > @@ -1087,9 +1087,29 @@ static void panthor_job_irq_handler(struct panthor_irq *pirq, u32 status)
> >         }
> >  }
> >
> > -static irqreturn_t panthor_job_irq_threaded_handler(int irq, void *data)
> > +static irqreturn_t panthor_job_irq_raw_handler(int irq, void *data)
> >  {
> > -       return panthor_irq_default_threaded_handler(data, panthor_job_irq_handler);
> > +       struct panthor_irq *pirq = data;
> > +
> > +       if (!gpu_read(pirq->iomem, INT_STAT))
> > +               return IRQ_NONE;
> > +
> > +       scoped_guard(spinlock_irqsave, &pirq->mask_lock) {
> > +               if (pirq->state != PANTHOR_IRQ_STATE_ACTIVE)
> > +                       return IRQ_NONE;
> > +
> > +               pirq->state = PANTHOR_IRQ_STATE_PROCESSING;
> > +       }
> > +
> > +       /* We can use INT_STAT here, because we didn't mask the IRQs. */
> > +       panthor_job_irq_handler(pirq, gpu_read(pirq->iomem, INT_STAT));
> We should loop here until INT_STAT is cleared.
Perhaps not. This is hardirq.

Reviewed-by: Chia-I Wu <olvaffe@gmail.com>
> > +
> > +       scoped_guard(spinlock_irqsave, &pirq->mask_lock) {
> > +               if (pirq->state == PANTHOR_IRQ_STATE_PROCESSING)
> > +                       pirq->state = PANTHOR_IRQ_STATE_ACTIVE;
> > +       }
> > +
> > +       return IRQ_HANDLED;
> >  }
> >
> >  static int panthor_fw_start(struct panthor_device *ptdev)
> > @@ -1489,8 +1509,7 @@ 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);
> > +                                 panthor_job_irq_raw_handler, NULL);
> >         if (ret) {
> >                 drm_err(&ptdev->base, "failed to request job irq");
> >                 return ret;
> >
> > --
> > 2.54.0
> >