linux-kernel - Re: [PATCH v2 1/3] dt-bindings: serial: Add Loongson UART controller

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Message-ID: <d9d76a4a-1552-462b-b946-6475645c6f59@kernel.org>
Date: Mon, 12 Aug 2024 10:25:36 +0200
From: Krzysztof Kozlowski <krzk@...nel.org>
To: 郑豪威 <zhenghaowei@...ngson.cn>,
 gregkh@...uxfoundation.org, jirislaby@...nel.org, robh@...nel.org,
 krzk+dt@...nel.org, conor+dt@...nel.org, chenhuacai@...nel.org,
 kernel@...0n.name, p.zabel@...gutronix.de, zhuyinbo <zhuyinbo@...ngson.cn>,
 Jianmin Lv <lvjianmin@...ngson.cn>, Liu Peibao <liupeibao@...ngson.cn>,
 wanghongliang <wanghongliang@...ngson.cn>
Cc: linux-serial@...r.kernel.org, linux-kernel@...r.kernel.org,
 devicetree@...r.kernel.org, loongarch@...ts.linux.dev
Subject: Re: [PATCH v2 1/3] dt-bindings: serial: Add Loongson UART controller

On 12/08/2024 10:09, 郑豪威 wrote:
> 
> 在 2024/8/9 18:05, Krzysztof Kozlowski 写道:
>> On 09/08/2024 11:55, 郑豪威 wrote:
>>>>>>> +    description: Enables fractional-N division. Currently,
>>>>>>> +      only LS2K1500 and LS2K2000 support this feature.
>>>>>>> +
>>>>>>> +  rts-invert:
>>>>>>> +    description: Inverts the RTS value in the MCR register.
>>>>>>> +      This should be used on Loongson-3 series CPUs, Loongson-2K
>>>>>>> +      series CPUs, and Loongson LS7A bridge chips.
>>>>>>> +
>>>>>>> +  dtr-invert:
>>>>>>> +    description: Inverts the DTR value in the MCR register.
>>>>>>> +      This should be used on Loongson-3 series CPUs, Loongson-2K
>>>>>>> +      series CPUs, and Loongson LS7A bridge chips.
>>>>>>> +
>>>>>>> +  cts-invert:
>>>>>>> +    description: Inverts the CTS value in the MSR register.
>>>>>>> +      This should be used on Loongson-2K0500, Loongson-2K1000,
>>>>>>> +      and Loongson LS7A bridge chips.
>>>>>>> +
>>>>>>> +  dsr-invert:
>>>>>>> +    description: Inverts the DSR value in the MSR register.
>>>>>>> +      This should be used on Loongson-2K0500, Loongson-2K1000,
>>>>>>> +      and Loongson LS7A bridge chips.
>>>> Same questions for all these. Why choosing invert is a board level
>>>> decision? If it "should be used" then why it is not used always?
>>>>
>>> Because these features are not applicable to all chips, such as
>>> 'fractional-division',
>> Hm?
>>
>>> which is currently supported only by 2K1500 and 2K2000, and for
>>> Loongson-3 series
>> These are SoCs. Compatible defines that. Please align with your
>> colleagues, because *we talked about this* already.
>>
>> Best regards,
>> Krzysztof
> 
> I consulted with my colleagues and would like to confirm with you. For 
> the five
> 
> properties provided, fractional-division is offered as a new feature,  
> supported by
> 
> 2K1500 and 2K2000. As for the invert property, it is due to a bug in our 
> controller,
> 
> and its usage may vary across different chips. Should we add different 
> compatible
> 
> values to address these issues for different chips, whether they are new 
> features or
> 
> controller bugs?

How did you align? We had already talks with you about this problem -
you need specific compatibles. How you explain above properties, all of
them are deducible from the compatible, so drop them.

Your entire argument above does not address at all my concerns, so
before you respond repeating the same, really talk with your colleagues.

One of many previous discussions:
https://lore.kernel.org/linux-devicetree/25c30964-6bd3-c7eb-640a-ba1f513b7675@linaro.org/

https://lore.kernel.org/linux-devicetree/20230526-dolly-reheat-06c4d5658415@wendy/

I wish we do not have to keep repeating the same to Loongson. Please
STORE the feedback for any future submissions, so you will not repeat
the same mistakes over and over.

Best regards,
Krzysztof