linux-kernel - Re: [PATCH v2 5/8] riscv: dts: renesas: Add initial devicetree for Renesas RZ/Five SoC

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Message-ID: <CAMuHMdXHSMcrVOH+vcrdRRF+i2TkMcFisGxHMBPUEa8nTMFpzw@mail.gmail.com>
Date:   Fri, 19 Aug 2022 10:04:43 +0200
From:   Geert Uytterhoeven <geert@...ux-m68k.org>
To:     Lad Prabhakar <prabhakar.mahadev-lad.rj@...renesas.com>
Cc:     Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Paul Walmsley <paul.walmsley@...ive.com>,
        Palmer Dabbelt <palmer@...belt.com>,
        Albert Ou <aou@...s.berkeley.edu>,
        Geert Uytterhoeven <geert+renesas@...der.be>,
        Conor Dooley <Conor.Dooley@...rochip.com>,
        Anup Patel <anup@...infault.org>,
        Linux-Renesas <linux-renesas-soc@...r.kernel.org>,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
        <devicetree@...r.kernel.org>,
        linux-riscv <linux-riscv@...ts.infradead.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Prabhakar <prabhakar.csengg@...il.com>,
        Biju Das <biju.das.jz@...renesas.com>
Subject: Re: [PATCH v2 5/8] riscv: dts: renesas: Add initial devicetree for
 Renesas RZ/Five SoC

Hi Prabhalar,

On Mon, Aug 15, 2022 at 5:17 PM Lad Prabhakar
<prabhakar.mahadev-lad.rj@...renesas.com> wrote:
> Add initial device tree for Renesas RZ/Five RISC-V CPU Core (AX45MP
> Single).
>
> Below is the list of IP blocks added in the initial SoC DTSI which can be
> used to boot via initramfs on RZ/Five SMARC EVK:
> - AX45MP CPU
> - CPG
> - PINCTRL
> - PLIC
> - SCIF0
> - SYSC
>
> Signed-off-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@...renesas.com>

Thanks for your patch!

> --- /dev/null
> +++ b/arch/riscv/boot/dts/renesas/r9a07g043.dtsi
> @@ -0,0 +1,121 @@
> +// SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
> +/*
> + * Device Tree Source for the RZ/Five SoC

My first thought was:

    This should be arch/riscv/boot/dts/renesas/r9a07g043f01.dtsi,
     including the common r9a07g043.dtsi, shared by
     arch/arm64/boot/dts/renesas/r9a07g043u11.dtsi.

Then I realized this is harder than it sounds, due:

> +       soc: soc {
> +               compatible = "simple-bus";
> +               interrupt-parent = <&plic>;

vs. "interrupt-parent = <&plic>;" for r9a07g043u11, but mostly
due to

> +               #address-cells = <2>;
> +               #size-cells = <2>;
> +               ranges;
> +
> +               scif0: serial@...4b800 {
> +                       compatible = "renesas,scif-r9a07g043",
> +                                    "renesas,scif-r9a07g044";
> +                       reg = <0 0x1004b800 0 0x400>;
> +                       interrupts = <412 IRQ_TYPE_LEVEL_HIGH>,
> +                                    <414 IRQ_TYPE_LEVEL_HIGH>,
> +                                    <415 IRQ_TYPE_LEVEL_HIGH>,
> +                                    <413 IRQ_TYPE_LEVEL_HIGH>,
> +                                    <416 IRQ_TYPE_LEVEL_HIGH>,
> +                                    <416 IRQ_TYPE_LEVEL_HIGH>;

vs. "interrupts = <GIC_SPI 380 IRQ_TYPE_LEVEL_HIGH> ..." on
r9a07g043u11.
Interestingly, the actual hardware interrupt numbers are the same,
but the GIC DT bindings abstracts the offset of 32 by using a second
cell and GIC_SPI.  Unfortunately this cannot be handled by some CPP
magic, as dtc does not support arithmetic operations yet.

I expect this or similar issues to pop up everywhere, when more
RISCV-V SoCs will appear that share the non-CPU parts with ARM SoCs.

Ignoring this issue, which we probably can solve only later:
Reviewed-by: Geert Uytterhoeven <geert+renesas@...der.be>

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