linux-kernel - Re: [PATCH v6 4/6] dt-bindings: cache: r9a07g043f-l2-cache: Add DT binding documentation for L2 cache controller

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Date:   Mon, 9 Jan 2023 13:15:39 +0100
From:   Geert Uytterhoeven <geert@...ux-m68k.org>
To:     "Lad, Prabhakar" <prabhakar.csengg@...il.com>
Cc:     Conor Dooley <conor@...nel.org>, Arnd Bergmann <arnd@...db.de>,
        Conor Dooley <conor.dooley@...rochip.com>,
        Heiko Stuebner <heiko@...ech.de>, Guo Ren <guoren@...nel.org>,
        Andrew Jones <ajones@...tanamicro.com>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Lad Prabhakar <prabhakar.mahadev-lad.rj@...renesas.com>,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
        <devicetree@...r.kernel.org>,
        open list <linux-kernel@...r.kernel.org>,
        linux-riscv@...ts.infradead.org, linux-renesas-soc@...r.kernel.org,
        Rob Herring <robh@...nel.org>
Subject: Re: [PATCH v6 4/6] dt-bindings: cache: r9a07g043f-l2-cache: Add DT
 binding documentation for L2 cache controller

Hi Prabhakar,

On Sat, Jan 7, 2023 at 9:47 PM Lad, Prabhakar
<prabhakar.csengg@...il.com> wrote:
> On Fri, Jan 6, 2023 at 9:53 PM Conor Dooley <conor@...nel.org> wrote:
> > On Fri, Jan 06, 2023 at 06:55:24PM +0000, Prabhakar wrote:
> > > From: Lad Prabhakar <prabhakar.mahadev-lad.rj@...renesas.com>
> > >
> > > Add DT binding documentation for L2 cache controller found on RZ/Five SoC.
> > >
> > > The Renesas RZ/Five microprocessor includes a RISC-V CPU Core (AX45MP
> > > Single) from Andes. The AX45MP core has an L2 cache controller, this patch
> > > describes the L2 cache block.
> > >
> > > Signed-off-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@...renesas.com>
> > > Reviewed-by: Rob Herring <robh@...nel.org>

> > > --- /dev/null
> > > +++ b/Documentation/devicetree/bindings/cache/andestech,ax45mp-cache.yaml
> > > @@ -0,0 +1,81 @@
> > > +# SPDX-License-Identifier: (GPL-2.0 OR BSD-2-Clause)
> > > +# Copyright (C) 2022 Renesas Electronics Corp.
> > > +%YAML 1.2
> > > +---
> > > +$id: http://devicetree.org/schemas/cache/andestech,ax45mp-cache.yaml#
> > > +$schema: http://devicetree.org/meta-schemas/core.yaml#
> > > +
> > > +title: Andestech AX45MP L2 Cache Controller
> > > +
> > > +maintainers:
> > > +  - Lad Prabhakar <prabhakar.mahadev-lad.rj@...renesas.com>
> > > +
> > > +description:
> > > +  A level-2 cache (L2C) is used to improve the system performance by providing
> > > +  a large amount of cache line entries and reasonable access delays. The L2C
> > > +  is shared between cores, and a non-inclusive non-exclusive policy is used.
> > > +
> > > +select:
> > > +  properties:
> > > +    compatible:
> > > +      contains:
> > > +        enum:
> > > +          - andestech,ax45mp-cache
> > > +
> > > +  required:
> > > +    - compatible
> > > +
> > > +properties:
> > > +  compatible:
> > > +    items:
> > > +      - const: andestech,ax45mp-cache
> > > +      - const: cache
> >
> > You might find value in a specific compatible for your SoC & enforce
> > constraints for it. Or you might not & I don't care either way :)
> >
> Good point actually. Geert what do you think?

That might be prudent, to cater for the way the standard AX45MP cache
block is integrated into the RZ/Five (or any other) SoC.

Still, in the absence of an SoC-specific compatible value, you can
handle integration issues using soc_device_match().

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