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Date:   Tue, 1 Aug 2023 16:54:21 +0100
From:   Conor Dooley <conor@kernel.org>
To:     Yinbo Zhu <zhuyinbo@loongson.cn>
Cc:     Linus Walleij <linus.walleij@linaro.org>,
        Bartosz Golaszewski <brgl@bgdev.pl>,
        Rob Herring <robh+dt@kernel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@linaro.org>,
        Conor Dooley <conor+dt@kernel.org>, linux-gpio@vger.kernel.org,
        devicetree@vger.kernel.org, linux-kernel@vger.kernel.org,
        Jianmin Lv <lvjianmin@loongson.cn>, wanghongliang@loongson.cn,
        Liu Peibao <liupeibao@loongson.cn>,
        loongson-kernel@lists.loongnix.cn
Subject: Re: [PATCH v2 1/2] gpio: dt-bindings: add parsing of loongson gpio
 offset
Message-ID: <20230801-varsity-chemo-09cc5e250ded@spud>
References: <20230731091059.17323-1-zhuyinbo@loongson.cn>
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On Tue, Aug 01, 2023 at 04:34:30PM +0800, Yinbo Zhu wrote:
>=20
>=20
> =E5=9C=A8 2023/8/1 =E4=B8=8B=E5=8D=883:23, Conor Dooley =E5=86=99=E9=81=
=93:
> > On Tue, Aug 01, 2023 at 02:39:49PM +0800, Yinbo Zhu wrote:
> > >=20
> > >=20
> > > =E5=9C=A8 2023/7/31 =E4=B8=8B=E5=8D=8811:55, Conor Dooley =E5=86=99=
=E9=81=93:
> > > > On Mon, Jul 31, 2023 at 05:10:58PM +0800, Yinbo Zhu wrote:
> > > > > Add parsing GPIO configure, input, output, interrupt register off=
set
> > > > > address and GPIO control mode support.
> > > >=20
> > > > This reeks of insufficient use of SoC specific compatibles. Do GPIO
> > > > controllers on the same SoC have different register offsets?
> > >=20
> > >=20
> > > Yes,
> > >=20
> > > > Where are the users for this?
> > >=20
> > >=20
> > > For example, ls2k500 contains multiple GPIO chips with different
> > > (configure, input, output, interrupt) offset addresses, but all others
> > > are the same.
> >=20
> > Right. That's admittedly not what I expected to hear! Can you firstly
> > explain this in the commit message,
>=20
>=20
> I will add following explain in the commit message. Do you think it's
> suitable?
>=20
> Loongson GPIO controllers come in multiple variants that are compatible
> except for certain register offset values.  Add support in yaml file for
> device properties allowing to specify them in DT.

Sure, that would be helpful.=20

> > and secondly add a soc-specific
> > compatible for the ls2k500 and only allow these properties on that SoC?

> Sorry, I may not have described it clearly before, the ls2k500 was only
> as a example, actually, Loongson GPIO controllers (2k500,2k1000,eg)come
> in multiple variants that are compatible except for certain register
> offset values.  So above all offset device property was used to in all
> loongson gpio controller.

But it would be good to know why they are different. Do they each
support some different features, or was there some other reason for
making controllers like this?

Thanks,
Conor.

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