linux-kernel - Re: [PATCH v2 01/12] dt-bindings: net: snps,dwmac: Allow exclusive usage of ahb reset

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Message-ID: <d532514a-524c-4607-b97b-2f89bc563406@collabora.com>
Date:   Mon, 30 Oct 2023 21:07:25 +0200
From:   Cristian Ciocaltea <cristian.ciocaltea@...labora.com>
To:     Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Conor Dooley <conor+dt@...nel.org>,
        Emil Renner Berthing <kernel@...il.dk>,
        Samin Guo <samin.guo@...rfivetech.com>,
        Paul Walmsley <paul.walmsley@...ive.com>,
        Palmer Dabbelt <palmer@...belt.com>,
        Albert Ou <aou@...s.berkeley.edu>,
        Alexandre Torgue <alexandre.torgue@...s.st.com>,
        Jose Abreu <joabreu@...opsys.com>,
        Maxime Coquelin <mcoquelin.stm32@...il.com>,
        Richard Cochran <richardcochran@...il.com>,
        Giuseppe Cavallaro <peppe.cavallaro@...com>
Cc:     netdev@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-riscv@...ts.infradead.org,
        linux-stm32@...md-mailman.stormreply.com,
        linux-arm-kernel@...ts.infradead.org, kernel@...labora.com
Subject: Re: [PATCH v2 01/12] dt-bindings: net: snps,dwmac: Allow exclusive
 usage of ahb reset

On 10/30/23 09:26, Krzysztof Kozlowski wrote:
> On 29/10/2023 23:24, Cristian Ciocaltea wrote:
>> On 10/29/23 13:25, Krzysztof Kozlowski wrote:
>>> On 29/10/2023 05:27, Cristian Ciocaltea wrote:
>>>> The Synopsys DesignWare MAC found on the StarFive JH7100 SoC requires
>>>> just the 'ahb' reset name, but the binding allows selecting it only in
>>>> conjunction with 'stmmaceth'.
>>>>
>>>> Fix the issue by permitting exclusive usage of the 'ahb' reset name.
>>>>
>>>> Signed-off-by: Cristian Ciocaltea <cristian.ciocaltea@...labora.com>
>>>> ---
>>>>  Documentation/devicetree/bindings/net/snps,dwmac.yaml | 2 +-
>>>>  1 file changed, 1 insertion(+), 1 deletion(-)
>>>>
>>>> diff --git a/Documentation/devicetree/bindings/net/snps,dwmac.yaml b/Documentation/devicetree/bindings/net/snps,dwmac.yaml
>>>> index 5c2769dc689a..a4d7172ea701 100644
>>>> --- a/Documentation/devicetree/bindings/net/snps,dwmac.yaml
>>>> +++ b/Documentation/devicetree/bindings/net/snps,dwmac.yaml
>>>> @@ -146,7 +146,7 @@ properties:
>>>>    reset-names:
>>>>      minItems: 1
>>>>      items:
>>>> -      - const: stmmaceth
>>>> +      - enum: [stmmaceth, ahb]
>>>
>>> Also, this makes sense only with patch #4, so this should be squashed there.
>>
>> I added this as a separate patch since it changes the generic schema
>> which is included by many other bindings.  JH7100 just happens to be the
>> first use-case requiring this update.  But I can squash the patch if
>> that's not a good enough reason to keep it separately.
> 
> If there is no single user of this, why changing this? I would even
> argue that it is not correct from existing bindings point of view -
> nothing allows and uses ahb as the only reset. Even the commit msg
> mentions your hardware from patch 4.

Sorry, I'm not sure I follow. JH7100 is (or will be) the user of it and,
as a matter of fact, something similar has been done recently while
adding support for JH7110.

In particular, commit [1] changed this binding before the JH7110
compatible was introduced in a subsequent patch. On a closer look that
commit made a statement which is not entirely correct:

"dwmac controller may require one (stmmaceth) or two (stmmaceth+ahb)
reset signals"

That's because stmmaceth is also optional in dwmac's driver, hence the
correct message would have been:

"[...] may require one (stmmaceth OR ahb) [...]"

Hence, I think it makes sense to keep this patch, after adding the above
details in the commit message.

[1] 843f603762a5 ("dt-bindings: net: snps,dwmac: Add 'ahb'
reset/reset-name")

Thanks,
Cristian