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: <IA1PR20MB4953EBB4DA58A7170D865B0CBBB2A@IA1PR20MB4953.namprd20.prod.outlook.com>
Date:   Tue, 14 Nov 2023 09:45:33 +0800
From:   Inochi Amaoto <inochiama@...look.com>
To:     Chen Wang <unicorn_wang@...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:     Inochi Amaoto <inochiama@...look.com>, 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?

Yes, that is right.

>Recommend to add some comment in binding file to make it clear.
>

Thanks for your advice.

>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
>>
>