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From:   Doug Anderson <dianders@chromium.org>
Date:   Tue, 19 Oct 2021 14:11:49 -0700
Message-ID: <CAD=FV=XsiMp5jSpX5ong27KYW=G-XYhCfjo48E5cC6Cm+oU-mA@mail.gmail.com>
Subject: Re: [PATCH V10 8/8] arm64: dts: sc7280: Add aliases for I2C and SPI
To:     Bjorn Andersson <bjorn.andersson@linaro.org>
Cc:     Arnd Bergmann <arnd@kernel.org>,
        Rajesh Patil <rajpat@codeaurora.org>,
        Andy Gross <agross@kernel.org>,
        Rob Herring <robh+dt@kernel.org>,
        linux-arm-msm <linux-arm-msm@vger.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        DTML <devicetree@vger.kernel.org>,
        Rajendra Nayak <rnayak@codeaurora.org>,
        Sai Prakash Ranjan <saiprakash.ranjan@codeaurora.org>,
        msavaliy@qti.qualcomm.com, satya priya <skakit@codeaurora.org>,
        Stephen Boyd <sboyd@kernel.org>,
        Matthias Kaehlcke <mka@chromium.org>
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Hi,

On Tue, Oct 19, 2021 at 1:57 PM Bjorn Andersson
<bjorn.andersson@linaro.org> wrote:
>
> On Tue 19 Oct 13:43 PDT 2021, Arnd Bergmann wrote:
>
> > On Thu, Sep 23, 2021 at 2:18 PM Rajesh Patil <rajpat@codeaurora.org> wrote:
> > >
> > > Add aliases for i2c and spi for sc7280 soc.
> > >
> > > Signed-off-by: Rajesh Patil <rajpat@codeaurora.org>
> > > Reviewed-by: Stephen Boyd <swboyd@chromium.org>
> >
> > I saw this in the pull request, can this please be reverted?
> >
>
> Yes, this can certainly be corrected.
>
> > Putting the aliases into the .dtsi file is really silly, as there are
> > likely boards that
> > don't connect every single one of those, and then will have to
> > override and renumber
> > them.
> >
> > Please only list the aliases that are actually connected on a particular
> > board.

Hrm. I know this gets into slightly controversial topics, but I'm a
little curious what the downside of having these in the dtsi is. In
the case where these i2c/spi/mmc devices _don't_ have "well defined"
numbers in the hardware manual of the SoC then I can agree that it
doesn't make sense to list these in the dtsi file. However, in the
case of sc7280 these numbers are well defined at the SoC level for i2c
and SPI.

Said another way: if you have a board that's got peripherals connected
on the pins labelled "i2c2" and "i2c6" on the SoC then it's a really
nice thing if these show up on /dev/i2c-2 and /dev/i2c-6.

...so I'm not sure what board exactly would be overriding and
re-numbering? Unless a board really has a strong use case where they
need the device connected to the pins for "i2c2" to show up on
"/dev/i2c-0"?


-Doug