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References: <20211015100941.17621-1-heinrich.schuchardt@canonical.com>
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From:   Bin Meng <bmeng.cn@gmail.com>
Date:   Fri, 15 Oct 2021 18:14:46 +0800
Message-ID: <CAEUhbmUSmi9mbiHpatBjGgRjrtyJPms9BRmyBPs5BWeVb7n1Nw@mail.gmail.com>
Subject: Re: [PATCH 1/1] dt-bindings: reg-io-width for SiFive CLINT
To:     Heinrich Schuchardt <heinrich.schuchardt@canonical.com>
Cc:     Daniel Lezcano <daniel.lezcano@linaro.org>,
        Thomas Gleixner <tglx@linutronix.de>,
        Guo Ren <guoren@linux.alibaba.com>, Xiang W <wxjstz@126.com>,
        Samuel Holland <samuel@sholland.org>,
        Atish Patra <atish.patra@wdc.com>,
        Rob Herring <robh+dt@kernel.org>,
        Palmer Dabbelt <palmer@dabbelt.com>,
        Paul Walmsley <paul.walmsley@sifive.com>,
        Anup Patel <anup.patel@wdc.com>,
        linux-kernel <linux-kernel@vger.kernel.org>,
        devicetree <devicetree@vger.kernel.org>,
        linux-riscv <linux-riscv@lists.infradead.org>,
        OpenSBI <opensbi@lists.infradead.org>
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On Fri, Oct 15, 2021 at 6:09 PM Heinrich Schuchardt
<heinrich.schuchardt@canonical.com> wrote:
>
> The CLINT in the T-HEAD 9xx processors do not support 64bit mmio access to
> the MTIMER device. The current schema does not allow to specify this.
>
> OpenSBI currently uses a property 'clint,has-no-64bit-mmio' to indicate the
> restriction. Samuael Holland suggested in
> lib: utils/timer: Use standard property to specify 32-bit I/O
> https://github.com/smaeul/opensbi/commit/b95e9cf7cf93b0af16fc89204378bc59ff30008e
> to use "reg-io-width = <4>;" as the reg-io-width property is generally used
> in the devicetree schema for such a condition.
>
> A release candidate of the ACLINT specification is available at
> https://github.com/riscv/riscv-aclint/releases
>
> Add reg-io-width as optional property to the SiFive Core Local Interruptor.
>
> Signed-off-by: Heinrich Schuchardt <heinrich.schuchardt@canonical.com>
> ---
>  Documentation/devicetree/bindings/timer/sifive,clint.yaml | 7 +++++++
>  1 file changed, 7 insertions(+)
>
> diff --git a/Documentation/devicetree/bindings/timer/sifive,clint.yaml b/Documentation/devicetree/bindings/timer/sifive,clint.yaml
> index a35952f48742..266012d887b5 100644
> --- a/Documentation/devicetree/bindings/timer/sifive,clint.yaml
> +++ b/Documentation/devicetree/bindings/timer/sifive,clint.yaml
> @@ -41,6 +41,13 @@ properties:
>    reg:
>      maxItems: 1
>
> +  reg-io-width:
> +    description: |
> +      Some CLINT implementations, e.g. on the T-HEAD 9xx, only support
> +      32bit access for MTIMER.
> +    $ref: /schemas/types.yaml#/definitions/uint32
> +    const: 4

But this is not a "sifive,clint" anyway. Should there be a new
dt-bindings for T-Head clint variant?

> +
>    interrupts-extended:
>      minItems: 1

Regards,
Bin