linux-kernel - Re: [PATCH v5 1/2] dt-bindings: timer: thead,c900-aclint-mtimer: separate mtime and mtimecmp regs

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Message-ID: <CAJF2gTSf5dCuYecY39nksczFzuXUvEJ_hLef5tyW0OgLmCDLPQ@mail.gmail.com>
Date:   Mon, 4 Dec 2023 22:52:48 +0800
From:   Guo Ren <guoren@...nel.org>
To:     Inochi Amaoto <inochiama@...look.com>
Cc:     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>,
        Chen Wang <unicorn_wang@...look.com>,
        Anup Patel <anup@...infault.org>,
        Samuel Holland <samuel.holland@...ive.com>,
        Jisheng Zhang <jszhang@...nel.org>,
        linux-kernel@...r.kernel.org, devicetree@...r.kernel.org,
        linux-riscv@...ts.infradead.org
Subject: Re: [PATCH v5 1/2] dt-bindings: timer: thead,c900-aclint-mtimer:
 separate mtime and mtimecmp regs

On Mon, Dec 4, 2023 at 5:51 PM Inochi Amaoto <inochiama@...look.com> 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 introduced a new type of T-HEAD aclint timer which
> has clint timer layout. Although it has the clint timer 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
> regs-names to represent the mtimecmp register, which can avoid hack
> for unsupport mtime register of T-HEAD aclint timer.
>
> Also, as T-HEAD aclint only supports mtimecmp, it is unnecessary to
> implement the whole aclint spec. To make this binding T-HEAD specific,
> only add reg-name for existed register. For details, see the discussion
> in the last link.
>
> 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
> Link: https://lore.kernel.org/all/IA1PR20MB4953F9D77FFC76A9D236922DBBB6A@IA1PR20MB4953.namprd20.prod.outlook.com/
> ---
>  .../bindings/timer/thead,c900-aclint-mtimer.yaml         | 9 ++++++++-
>  1 file changed, 8 insertions(+), 1 deletion(-)
>
> diff --git a/Documentation/devicetree/bindings/timer/thead,c900-aclint-mtimer.yaml b/Documentation/devicetree/bindings/timer/thead,c900-aclint-mtimer.yaml
> index fbd235650e52..2e92bcdeb423 100644
> --- a/Documentation/devicetree/bindings/timer/thead,c900-aclint-mtimer.yaml
> +++ b/Documentation/devicetree/bindings/timer/thead,c900-aclint-mtimer.yaml
> @@ -17,7 +17,12 @@ properties:
>        - const: thead,c900-aclint-mtimer
>
>    reg:
> -    maxItems: 1
> +    items:
> +      - description: MTIMECMP Registers
> +
> +  reg-names:
> +    items:
> +      - const: mtimecmp
>
>    interrupts-extended:
>      minItems: 1
> @@ -28,6 +33,7 @@ additionalProperties: false
>  required:
>    - compatible
>    - reg
> +  - reg-names
>    - interrupts-extended
>
>  examples:
> @@ -39,5 +45,6 @@ examples:
>                              <&cpu3intc 7>,
>                              <&cpu4intc 7>;
>        reg = <0xac000000 0x00010000>;
> +      reg-names = "mtimecmp";
>      };
>  ...
> --
> 2.43.0
>
Acked-by: Guo Ren <guoren@...nel.org>

-- 
Best Regards
 Guo Ren