linux-kernel - Re: [PATCH 4/9] dt-bindings: Add RISC-V incoming MSI controller bindings

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Date:   Wed, 16 Nov 2022 13:29:33 +0000
From:   Conor Dooley <conor.dooley@...rochip.com>
To:     Anup Patel <apatel@...tanamicro.com>
CC:     Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>,
        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 4/9] dt-bindings: Add RISC-V incoming MSI controller
 bindings

On Wed, Nov 16, 2022 at 04:04:45PM +0530, Anup Patel wrote:
> On Wed, Nov 16, 2022 at 2:30 PM Krzysztof Kozlowski
> <krzysztof.kozlowski@...aro.org> wrote:
> >
> > On 15/11/2022 23:34, Conor Dooley wrote:
> > > On Mon, Nov 14, 2022 at 05:59:00PM +0530, Anup Patel wrote:
> > >> On Sun, Nov 13, 2022 at 8:18 PM Conor Dooley <conor@...nel.org> wrote:
> > >
> > >>> Also, the file name says "riscv,imsic", the description says "IMSIC" but
> > >>> you've used "imsics" in the compatible. Is this a typo, or a plural?
> > >>
> > >> Yes, the file name should be consistent. I will update the file name.
> > >
> > > Is there a reason why the compatible is plural when all of the other
> > > mentions etc do not have an "s"? It really did look like a typo to me.
> > >
> > > It's the "incoming MSI controller", so I am unsure as to where the "s"
> > > actually even comes from. Why not just use "riscv,imsic"?
> >
> > Yep, should be rather consistent with all others, and IMSIC stands for
> > Integrated Circuit?
> 
> This is intentionally plural because even though we have one
> IMSIC per-CPU, Linux (and various OSes) expect one DT node
> as MSI controller targeting all CPUs.

Even still, calling it "riscv,imsic" would seem fair to me given the
multiple regs make the distinct regions clear.

I think I must have missed the bit at the end of the description though:

+  The device tree of a RISC-V platform will have one IMSIC device tree node
+  for each privilege level (machine or supervisor) which collectively describe
+  IMSIC interrupt files at that privilege level across CPUs (or HARTs).

Perhaps, for eejits like me, that paragraph should become paragraph 3
instead of hiding it below the register layout etc?

Anyways, existing name seems fine to me then w/ the filename update &
increased prominence of the many-controllers-in-one statement.

Maybe the devicetree gods think differently!

> The plural compatible string "riscv,imsics" was chosen based
> on consensus on RISC-V AIA Task Group meetings.

btw, I see the following in the example:

+      reg = <0x28000000 0x2000>, /* Group0 IMSICs */
+            <0x29000000 0x2000>; /* Group1 IMSICs */

And in the property:
+  reg:
+    minItems: 1
+    maxItems: 128
+    description:
+      Base address of each IMSIC group.

It would appear that the comment there conflicts with the description of
the reg property itself & it's that lack of consistency me confused (:
Should the comments be in the singular form?

Thanks,
Conor.