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Date:   Mon, 27 Jun 2022 14:53:44 +0100
From:   Marc Zyngier <maz@kernel.org>
To:     Geert Uytterhoeven <geert@linux-m68k.org>
Cc:     "Lad, Prabhakar" <prabhakar.csengg@gmail.com>,
        Lad Prabhakar <prabhakar.mahadev-lad.rj@bp.renesas.com>,
        Thomas Gleixner <tglx@linutronix.de>,
        Rob Herring <robh+dt@kernel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@linaro.org>,
        Sagar Kadam <sagar.kadam@sifive.com>,
        Palmer Dabbelt <palmer@dabbelt.com>,
        Paul Walmsley <paul.walmsley@sifive.com>,
        linux-riscv <linux-riscv@lists.infradead.org>,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
        <devicetree@vger.kernel.org>,
        Geert Uytterhoeven <geert+renesas@glider.be>,
        Linux-Renesas <linux-renesas-soc@vger.kernel.org>,
        LKML <linux-kernel@vger.kernel.org>,
        Biju Das <biju.das.jz@bp.renesas.com>
Subject: Re: [PATCH v2 2/2] irqchip/sifive-plic: Add support for Renesas
 RZ/Five SoC
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On 2022-06-27 14:12, Geert Uytterhoeven wrote:
> Hi Prabhakar,
> 
> On Mon, Jun 27, 2022 at 3:06 PM Lad, Prabhakar
> <prabhakar.csengg@gmail.com> wrote:
>> On Mon, Jun 27, 2022 at 9:53 AM Geert Uytterhoeven 
>> <geert@linux-m68k.org> wrote:
>> > On Sun, Jun 26, 2022 at 2:19 PM Marc Zyngier <maz@kernel.org> wrote:
>> > > On Sun, 26 Jun 2022 10:38:18 +0100,
>> > > "Lad, Prabhakar" <prabhakar.csengg@gmail.com> wrote:
>> > > > On Sun, Jun 26, 2022 at 9:56 AM Marc Zyngier <maz@kernel.org> wrote:
>> > > > > On Sun, 26 Jun 2022 01:43:26 +0100,
>> > > > > 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>
>> >
>> > > > > > +     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.

But it will make a difference on a 64bit platform, as we want to
use test_bit() and co to check for features.

         M.
-- 
Jazz is not dead. It just smells funny...