Re: [PATCH 3/3] drm/panfrost: Stay in the threaded MMU IRQ handler until we've handled all IRQs

[Rob Herring <robh+dt@kernel.org>]

On Mon, Feb 1, 2021 at 2:21 AM Boris Brezillon
<boris.brezillon@collabora.com> wrote:
>
> Doing a hw-irq -> threaded-irq round-trip is counter-productive, stay
> in the threaded irq handler as long as we can.
>
> Signed-off-by: Boris Brezillon <boris.brezillon@collabora.com>
> ---
>  drivers/gpu/drm/panfrost/panfrost_mmu.c | 7 +++++++
>  1 file changed, 7 insertions(+)
>
> diff --git a/drivers/gpu/drm/panfrost/panfrost_mmu.c b/drivers/gpu/drm/panfrost/panfrost_mmu.c
> index 21e552d1ac71..65bc20628c4e 100644
> --- a/drivers/gpu/drm/panfrost/panfrost_mmu.c
> +++ b/drivers/gpu/drm/panfrost/panfrost_mmu.c
> @@ -580,6 +580,8 @@ static irqreturn_t panfrost_mmu_irq_handler_thread(int irq, void *data)
>         u32 status = mmu_read(pfdev, MMU_INT_RAWSTAT);
>         int i, ret;
>
> +again:
> +
>         for (i = 0; status; i++) {
>                 u32 mask = BIT(i) | BIT(i + 16);
>                 u64 addr;
> @@ -628,6 +630,11 @@ static irqreturn_t panfrost_mmu_irq_handler_thread(int irq, void *data)
>                 status &= ~mask;
>         }
>
> +       /* If we received new MMU interrupts, process them before returning. */
> +       status = mmu_read(pfdev, MMU_INT_RAWSTAT);
> +       if (status)
> +               goto again;
> +

Can't we avoid the goto? Change the for loop like this:

i = 0;
while (status = mmu_read(pfdev, MMU_INT_RAWSTAT)) {
    ...

    i++;
    if (i == 16)
        i = 0;
}

>         mmu_write(pfdev, MMU_INT_MASK, ~0);
>         return IRQ_HANDLED;
>  };
> --
> 2.26.2
>
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