Re: [PATCH RFC 2/2] irqchip/sifive-plic: Add support for Renesas RZ/Five SoC

[Geert Uytterhoeven <geert@linux-m68k.org>]

Hi Prabhakar,

On Tue, May 24, 2022 at 7:22 PM Lad Prabhakar
<prabhakar.mahadev-lad.rj@bp.renesas.com> wrote:
> The Renesas RZ/Five SoC has a RISC-V AX45MP AndesCore with NCEPLIC100. The
> NCEPLIC100 supports both edge-triggered and level-triggered interrupts. In
> case of edge-triggered interrupts NCEPLIC100 ignores the next interrupt
> edge until the previous completion message has been received and
> NCEPLIC100 doesn't support pending interrupt counter, hence losing the
> interrupts if not acknowledged in time.
>
> So the workaround for edge-triggered interrupts to be handled correctly
> and without losing is that it needs to be acknowledged first and then
> handler must be run so that we don't miss on the next edge-triggered
> interrupt.
>
> This patch adds a new compatible string for Renesas RZ/Five SoC and adds
> support to change interrupt flow based on the interrupt type. It also
> implements irq_ack and irq_set_type callbacks.
>
> Signed-off-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@bp.renesas.com>

Thanks for your patch!

> --- a/drivers/irqchip/irq-sifive-plic.c
> +++ b/drivers/irqchip/irq-sifive-plic.c
> @@ -60,10 +60,13 @@
>  #define        PLIC_DISABLE_THRESHOLD          0x7
>  #define        PLIC_ENABLE_THRESHOLD           0
>
> +#define RENESAS_R9A07G043_PLIC         1
> +
>  struct plic_priv {
>         struct cpumask lmask;
>         struct irq_domain *irqdomain;
>         void __iomem *regs;
> +       u8 of_data;

Usually it's cleaner to use feature bits instead of enum types.

>  };
>
>  struct plic_handler {
> @@ -163,10 +166,31 @@ static int plic_set_affinity(struct irq_data *d,
>  }
>  #endif
>
> +static void plic_irq_ack(struct irq_data *d)
> +{
> +       struct plic_handler *handler = this_cpu_ptr(&plic_handlers);
> +

No check for RZ/Five or irq type?
.irq_ack() seems to be called for level interrupts, too
(from handle_level_irq() through mask_ack_irq()).

> +       if (irqd_irq_masked(d)) {
> +               plic_irq_unmask(d);
> +               writel(d->hwirq, handler->hart_base + CONTEXT_CLAIM);
> +               plic_irq_mask(d);
> +       } else {
> +               writel(d->hwirq, handler->hart_base + CONTEXT_CLAIM);
> +       }
> +}

The above is identical to the old plic_irq_eoi()...

> +
>  static void plic_irq_eoi(struct irq_data *d)
>  {
>         struct plic_handler *handler = this_cpu_ptr(&plic_handlers);
>
> +       /*
> +        * For Renesas R9A07G043 SoC if the interrupt type is EDGE
> +        * we have already acknowledged it in ack callback.
> +        */
> +       if (handler->priv->of_data == RENESAS_R9A07G043_PLIC &&
> +           !irqd_is_level_type(d))
> +               return;
> +

... so you can just call into plic_irq_ack() here?

>         if (irqd_irq_masked(d)) {
>                 plic_irq_unmask(d);
>                 writel(d->hwirq, handler->hart_base + CONTEXT_CLAIM);
> @@ -176,11 +200,37 @@ static void plic_irq_eoi(struct irq_data *d)
>         }
>  }
>
> +static int plic_irq_set_type(struct irq_data *d, unsigned int type)
> +{
> +       struct plic_handler *handler = this_cpu_ptr(&plic_handlers);
> +
> +       if (handler->priv->of_data != RENESAS_R9A07G043_PLIC)
> +               return 0;
> +
> +       switch (type) {
> +       case IRQ_TYPE_LEVEL_HIGH:
> +               irq_set_handler_locked(d, handle_fasteoi_irq);
> +               break;
> +
> +       case IRQ_TYPE_EDGE_RISING:
> +               irq_set_handler_locked(d, handle_fasteoi_ack_irq);
> +               break;
> +
> +       default:
> +               return -EINVAL;
> +       }
> +
> +       return 0;
> +}
> +
>  static struct irq_chip plic_chip = {

I think this can be const.

>         .name           = "SiFive PLIC",
>         .irq_mask       = plic_irq_mask,
>         .irq_unmask     = plic_irq_unmask,
> +       .irq_ack        = plic_irq_ack,

This causes extra processing on non-affected PLICs.
Perhaps use a separate irq_chip instance?

>         .irq_eoi        = plic_irq_eoi,
> +       .irq_set_type   = plic_irq_set_type,
> +
>  #ifdef CONFIG_SMP
>         .irq_set_affinity = plic_set_affinity,
>  #endif
> @@ -198,6 +248,19 @@ static int plic_irqdomain_map(struct irq_domain *d, unsigned int irq,
>         return 0;
>  }
>
> +static int plic_irq_domain_translate(struct irq_domain *d,
> +                                    struct irq_fwspec *fwspec,
> +                                    unsigned long *hwirq,
> +                                    unsigned int *type)
> +{
> +       struct plic_priv *priv = d->host_data;
> +
> +       if (priv->of_data == RENESAS_R9A07G043_PLIC)
> +               return irq_domain_translate_twocell(d, fwspec, hwirq, type);
> +
> +       return irq_domain_translate_onecell(d, fwspec, hwirq, type);

This one clearly shows the discerning feature: onecell or twocell...

> +}
> +
>  static int plic_irq_domain_alloc(struct irq_domain *domain, unsigned int virq,
>                                  unsigned int nr_irqs, void *arg)
>  {

> @@ -293,6 +356,9 @@ static int __init plic_init(struct device_node *node,
>         if (!priv)
>                 return -ENOMEM;
>
> +       if (of_device_is_compatible(node, "renesas-r9a07g043-plic"))
> +               priv->of_data = RENESAS_R9A07G043_PLIC;
> +

So perhaps instead just look at #interrupt-cells, and use the onecell
or twocell irq_chip/irq_domain_ops based on that?

>         priv->regs = of_iomap(node, 0);
>         if (WARN_ON(!priv->regs)) {
>                 error = -EIO;

Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds