linux-kernel - Re: [PATCH v2 6/9] dt-bindings: interrupt-controller: Add RISC-V advanced PLIC

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Date:   Mon, 20 Feb 2023 10:56:23 +0000
From:   Conor Dooley <conor.dooley@...rochip.com>
To:     Anup Patel <apatel@...tanamicro.com>
CC:     Conor Dooley <conor@...nel.org>,
        Palmer Dabbelt <palmer@...belt.com>,
        Paul Walmsley <paul.walmsley@...ive.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Marc Zyngier <maz@...nel.org>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Atish Patra <atishp@...shpatra.org>,
        Alistair Francis <Alistair.Francis@....com>,
        Anup Patel <anup@...infault.org>,
        <linux-riscv@...ts.infradead.org>, <linux-kernel@...r.kernel.org>,
        <devicetree@...r.kernel.org>
Subject: Re: [PATCH v2 6/9] dt-bindings: interrupt-controller: Add RISC-V
 advanced PLIC

On Mon, Feb 20, 2023 at 10:32:57AM +0000, Conor Dooley wrote:
> On Mon, Feb 20, 2023 at 10:06:49AM +0530, Anup Patel wrote:
> > On Thu, Jan 5, 2023 at 3:47 AM Conor Dooley <conor@...nel.org> wrote:
> > > On Tue, Jan 03, 2023 at 07:44:06PM +0530, Anup Patel wrote:
> > > > We add DT bindings document for RISC-V advanced platform level
> > > > interrupt controller (APLIC) defined by the RISC-V advanced
> > > > interrupt architecture (AIA) specification.
> > > >
> > > > Signed-off-by: Anup Patel <apatel@...tanamicro.com>
> > > > ---
> > > >  .../interrupt-controller/riscv,aplic.yaml     | 159 ++++++++++++++++++
> > > >  1 file changed, 159 insertions(+)
> > > >  create mode 100644 Documentation/devicetree/bindings/interrupt-controller/riscv,aplic.yaml
> 
> > > I'm sorry Anup, but this child versus delegate thing is still not clear
> > > to me binding wise. See below.
> > 
> > There are two different information in-context of APLIC domain:
> > 
> > 1) HW child domain numbering: If an APLIC domain has N children
> >     then HW will have a fixed child index for each of the N children
> >     in the range 0 to N-1. This HW child index is required at the time
> >     of setting up interrupt delegation in sourcecfgX registers. The
> >     "riscv,children" DT property helps firmware (or bootloader) find
> >     the total number of child APLIC domains and corresponding
> >     HW child index number.
> > 
> > 2) IRQ delegation to child domains: An APLIC domain can delegate
> >    any IRQ range(s) to a particular APLIC child domain. The
> >    "riscv,delegate" DT property is simply a table where we have
> >    one row for each IRQ range which is delegated to some child
> >    APLIC domain. This property is more of a system setting fixed
> >    by the RISC-V platform vendor.
> 
> Thanks for the explanations. It's been a while since my brain swapped
> this stuff out, but I think delegate/child makes sense to me now.

> Just don't ask me to write the dt entry as proof...

Having looked at Dramforever's QEMU dtb dump a bit more and your
responses to her, I think that I have "come to terms" with it now
actually.
I suppose when the next version comes around I'll make sure that I
arrive in the same ballpark that QEMU does, based off the descriptions
etc in the binding.

Thanks!

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