linux-kernel - Re: [PATCH v2 2/2] irqchip/sifive-plic: Add support for Renesas RZ/Five SoC

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Date:   Mon, 27 Jun 2022 15:12:32 +0200
From:   Geert Uytterhoeven <geert@...ux-m68k.org>
To:     "Lad, Prabhakar" <prabhakar.csengg@...il.com>
Cc:     Marc Zyngier <maz@...nel.org>,
        Lad Prabhakar <prabhakar.mahadev-lad.rj@...renesas.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Sagar Kadam <sagar.kadam@...ive.com>,
        Palmer Dabbelt <palmer@...belt.com>,
        Paul Walmsley <paul.walmsley@...ive.com>,
        linux-riscv <linux-riscv@...ts.infradead.org>,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
        <devicetree@...r.kernel.org>,
        Geert Uytterhoeven <geert+renesas@...der.be>,
        Linux-Renesas <linux-renesas-soc@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Biju Das <biju.das.jz@...renesas.com>
Subject: Re: [PATCH v2 2/2] irqchip/sifive-plic: Add support for Renesas
 RZ/Five SoC

Hi Prabhakar,

On Mon, Jun 27, 2022 at 3:06 PM Lad, Prabhakar
<prabhakar.csengg@...il.com> wrote:
> On Mon, Jun 27, 2022 at 9:53 AM Geert Uytterhoeven <geert@...ux-m68k.org> wrote:
> > On Sun, Jun 26, 2022 at 2:19 PM Marc Zyngier <maz@...nel.org> wrote:
> > > On Sun, 26 Jun 2022 10:38:18 +0100,
> > > "Lad, Prabhakar" <prabhakar.csengg@...il.com> wrote:
> > > > On Sun, Jun 26, 2022 at 9:56 AM Marc Zyngier <maz@...nel.org> wrote:
> > > > > On Sun, 26 Jun 2022 01:43:26 +0100,
> > > > > Lad Prabhakar <prabhakar.mahadev-lad.rj@...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@...renesas.com>
> >
> > > > > > +     if (of_device_is_compatible(node, "renesas,r9a07g043-plic")) {
> > > > > > +             priv->of_data = RENESAS_R9A07G043_PLIC;
> > > > > > +             plic_chip.name = "Renesas RZ/Five PLIC";
> > > > >
> > > > > NAK. The irq_chip structure isn't the place for platform marketing.
> > > > > This is way too long anyway (and same for the edge version), and you
> > > > > even sent me a patch to make that structure const...
> > > > >
> > > > My bad will drop this.
> > >
> > > And why you're at it, please turn this rather random 'of_data' into
> > > something like:
> > >
> > > diff --git a/drivers/irqchip/irq-sifive-plic.c b/drivers/irqchip/irq-sifive-plic.c
> > > index bb87e4c3b88e..cd1683b77caf 100644
> > > --- a/drivers/irqchip/irq-sifive-plic.c
> > > +++ b/drivers/irqchip/irq-sifive-plic.c
> > > @@ -64,6 +64,10 @@ struct plic_priv {
> > >         struct cpumask lmask;
> > >         struct irq_domain *irqdomain;
> > >         void __iomem *regs;
> > > +       enum {
> > > +               VANILLA_PLIC,
> > > +               RENESAS_R9A07G043_PLIC,
> > > +       } flavour;
> > >  };
> > >
> > >  struct plic_handler {
> > >
> > > to give some structure to the whole thing, because I'm pretty sure
> > > we'll see more braindead implementations as time goes by.
> >
> > What about using a feature flag (e.g. had_edge_irqs) instead?
>
> diff --git a/drivers/irqchip/irq-sifive-plic.c
> b/drivers/irqchip/irq-sifive-plic.c
> index 9f16833dcb41..247c3c98b655 100644
> --- a/drivers/irqchip/irq-sifive-plic.c
> +++ b/drivers/irqchip/irq-sifive-plic.c
> @@ -60,13 +60,13 @@
>  #define        PLIC_DISABLE_THRESHOLD          0x7
>  #define        PLIC_ENABLE_THRESHOLD           0
>
> +#define PLIC_QUIRK_EDGE_INTERRUPT      BIT(0)
>
>  struct plic_priv {
>         struct cpumask lmask;
>         struct irq_domain *irqdomain;
>         void __iomem *regs;
> +       u32 plic_quirks;
>  };
>
> What about something like above?

LGTM.

Marc suggested to make this unsigned long, but TBH, that won't make
much of a difference.  PLICs are present on RV32 SoCs, too, so you
cannot rely on having more than 32 bits anyway.

Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-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