linux-kernel - Re: [RFC PATCH v3 06/11] dt-bindings: timer: Update SiFive CLINT bindings for IPI support

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Message-ID: <CAAhSdy1A-2oPVfWioqc7JDsRTHEgwMNR5zuVg-O-X0K86-7Exg@mail.gmail.com>
Date:   Thu, 2 Sep 2021 11:07:49 +0530
From:   Anup Patel <anup@...infault.org>
To:     Rob Herring <robh@...nel.org>
Cc:     Anup Patel <anup.patel@....com>,
        Palmer Dabbelt <palmer@...belt.com>,
        Palmer Dabbelt <palmerdabbelt@...gle.com>,
        Paul Walmsley <paul.walmsley@...ive.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Marc Zyngier <maz@...nel.org>,
        Daniel Lezcano <daniel.lezcano@...aro.org>,
        Atish Patra <atish.patra@....com>,
        Alistair Francis <Alistair.Francis@....com>,
        linux-riscv <linux-riscv@...ts.infradead.org>,
        "linux-kernel@...r.kernel.org List" <linux-kernel@...r.kernel.org>,
        DTML <devicetree@...r.kernel.org>
Subject: Re: [RFC PATCH v3 06/11] dt-bindings: timer: Update SiFive CLINT
 bindings for IPI support

On Thu, Sep 2, 2021 at 5:48 AM Rob Herring <robh@...nel.org> wrote:
>
> On Wed, Sep 1, 2021 at 7:00 AM Anup Patel <anup@...infault.org> wrote:
> >
> > On Wed, Sep 1, 2021 at 6:59 AM Rob Herring <robh@...nel.org> wrote:
> > >
> > > On Mon, Aug 30, 2021 at 09:47:24AM +0530, Anup Patel wrote:
> > > > The Linux RISC-V now treats IPIs as regular per-CPU IRQs. This means
> > > > we have to create a IPI interrupt domain to use CLINT IPI functionality
> > > > hence requiring a "interrupt-controller" and "#interrupt-cells" DT
> > > > property in CLINT DT nodes.
> > > >
> > > > Impact of this CLINT DT bindings change only affects Linux RISC-V
> > > > NoMMU kernel and has no effect of existing M-mode runtime firmwares
> > > > (i.e. OpenSBI).
> > >
> > > It appears to me you should fix Linux to not need these 2 useless
> > > properties. I say useless because #interrupt-cells being 0 is pretty
> > > useless.
> >
> > Linux IRQCHIP framework only probes IRQCHIP DT nodes which
> > have "interrupt-controller" DT property.
>
> Right, I believe I wrote that... So what would it look like to fix
> that? The simplest thing is just drop the check for
> 'interrupt-controller'. That's just a sanity check and we have other
> ways to do that now (schemas). Do you need this early? You can always
> implement your own initcall.

Okay, let me first try to fix this in the driver itself. Most likely,
we will not
require changes in this DT binding.

>
>
> > The "interrupt-cells" DT property
> > can be removed because as an interrupt controller SiFive CLINT
> > will only provide IPIs to arch code.
>
> The schema will disagree.

Okay.

>
> Rob

Regards,
Anup