linux-kernel - Re: [PATCH v2 1/2] dt-bindings: timer: thead,c900-aclint-mtimer: separate mtime and mtimecmp regs

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Message-ID: <MA0P287MB03326F420E96FE3198C81C21FEB2A@MA0P287MB0332.INDP287.PROD.OUTLOOK.COM>
Date:   Tue, 14 Nov 2023 09:09:15 +0800
From:   Chen Wang <unicorn_wang@...look.com>
To:     Inochi Amaoto <inochiama@...look.com>,
        Daniel Lezcano <daniel.lezcano@...aro.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Conor Dooley <conor+dt@...nel.org>,
        Paul Walmsley <paul.walmsley@...ive.com>,
        Palmer Dabbelt <palmer@...belt.com>,
        Albert Ou <aou@...s.berkeley.edu>
Cc:     Guo Ren <guoren@...nel.org>, Jisheng Zhang <jszhang@...nel.org>,
        linux-kernel@...r.kernel.org, devicetree@...r.kernel.org,
        linux-riscv@...ts.infradead.org
Subject: Re: [PATCH v2 1/2] dt-bindings: timer: thead,c900-aclint-mtimer:
 separate mtime and mtimecmp regs


On 2023/11/14 8:45, Inochi Amaoto wrote:
> The timer registers of aclint don't follow the clint layout and can
> be mapped on any different offset. As sg2042 uses separated timer
> and mswi for its clint, it should follow the aclint spec and have
> separated registers.
>
> The previous patch introduces a new type of T-HEAD aclint timer which
> has clint timer layout. Although the timer has the clint layout, it
> should follow the aclint spec and uses the separated mtime and mtimecmp
> regs. So a ABI change is needed to make the timer fit the aclint spec.
>
> To make T-HEAD aclint timer more closer to the aclint spec, use two regs
> to represent the mtime and mtimecmp.
>
> Signed-off-by: Inochi Amaoto <inochiama@...look.com>
> Fixes: 4734449f7311 ("dt-bindings: timer: Add Sophgo sg2042 CLINT timer")
> Link: https://lists.infradead.org/pipermail/opensbi/2023-October/005693.html
> Link: https://github.com/riscv/riscv-aclint/blob/main/riscv-aclint.adoc
> ---
>   .../devicetree/bindings/timer/thead,c900-aclint-mtimer.yaml  | 5 +++--
>   1 file changed, 3 insertions(+), 2 deletions(-)
>
> diff --git a/Documentation/devicetree/bindings/timer/thead,c900-aclint-mtimer.yaml b/Documentation/devicetree/bindings/timer/thead,c900-aclint-mtimer.yaml
> index fbd235650e52..c3080962d902 100644
> --- a/Documentation/devicetree/bindings/timer/thead,c900-aclint-mtimer.yaml
> +++ b/Documentation/devicetree/bindings/timer/thead,c900-aclint-mtimer.yaml
> @@ -17,7 +17,7 @@ properties:
>         - const: thead,c900-aclint-mtimer
>
>     reg:
> -    maxItems: 1
> +    maxItems: 2

The first one is for mtime and the second one is for mtimecmp, right? 
Recommend to add some comment in binding file to make it clear.

Chen

>
>     interrupts-extended:
>       minItems: 1
> @@ -38,6 +38,7 @@ examples:
>                               <&cpu2intc 7>,
>                               <&cpu3intc 7>,
>                               <&cpu4intc 7>;
> -      reg = <0xac000000 0x00010000>;
> +      reg = <0xac000000 0x00000000>,
> +            <0xac000000 0x0000c000>;
>       };
>   ...
> --
> 2.42.1
>