linux-kernel - Re: [PATCH v3 1/2] gpio: dt-bindings: add parsing of loongson gpio offset

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Message-ID: <20230809-circus-photo-6911d2e18f96@spud>
Date:   Wed, 9 Aug 2023 16:39:25 +0100
From:   Conor Dooley <conor@...nel.org>
To:     Yinbo Zhu <zhuyinbo@...ngson.cn>
Cc:     Linus Walleij <linus.walleij@...aro.org>,
        Bartosz Golaszewski <brgl@...ev.pl>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Conor Dooley <conor+dt@...nel.org>, linux-gpio@...r.kernel.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        Jianmin Lv <lvjianmin@...ngson.cn>, wanghongliang@...ngson.cn,
        loongson-kernel@...ts.loongnix.cn
Subject: Re: [PATCH v3 1/2] gpio: dt-bindings: add parsing of loongson gpio
 offset

On Wed, Aug 09, 2023 at 03:47:55PM +0800, Yinbo Zhu wrote:
> 在 2023/8/8 下午8:05, Conor Dooley 写道:
> > On Mon, Aug 07, 2023 at 03:40:42PM +0800, Yinbo Zhu wrote:

> > > +  loongson,gpio-ctrl-mode:
> > > +    $ref: /schemas/types.yaml#/definitions/uint32
> > > +    description:
> > > +      This option indicate this GPIO control mode, where '0' represents
> > > +      bit control mode and '1' represents byte control mode.
> > 
> > How is one supposed to know which of these modes to use?
> 
> 
> Byte mode is to access by byte, such as gpio3, the base address of the
> gpio controller is offset by 3 bytes as the access address of gpio3.
> 
> The bit mode is the normal mode that like other platform gpio and it is
> to access by bit.
> 
> If both modes are supported, it is recommended to prioritize using byte
> mode that according to spec.

So, sounds like this property should instead be a boolean that notes
whether the hardware supports the mode or not, rather than the current
enum used to determine software policy.

However, from Krzysztof's comments & my own feeling, it really does seem
like you should drop the do-everything compatible and introduce things
that are soc-specific.

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