linux-kernel - Re: [PATCH v1] of: property: Add fw_devlink support for "gpio" and "gpios" binding

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Message-ID: <CAGETcx-Vp0BpYbpPjwsmOv0q5ba1mJvfsPEZ9Oi2Rmx67udu7A@mail.gmail.com>
Date:   Tue, 19 Jan 2021 09:53:53 -0800
From:   Saravana Kannan <saravanak@...gle.com>
To:     Linus Walleij <linus.walleij@...aro.org>
Cc:     Geert Uytterhoeven <geert@...ux-m68k.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Rob Herring <robh+dt@...nel.org>,
        Frank Rowand <frowand.list@...il.com>,
        linux-tegra <linux-tegra@...r.kernel.org>,
        Bartosz Golaszewski <bgolaszewski@...libre.com>,
        Jon Hunter <jonathanh@...dia.com>,
        Android Kernel Team <kernel-team@...roid.com>,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
        <devicetree@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v1] of: property: Add fw_devlink support for "gpio" and
 "gpios" binding

On Tue, Jan 19, 2021 at 2:20 AM Linus Walleij <linus.walleij@...aro.org> wrote:
>
> On Tue, Jan 19, 2021 at 9:50 AM Geert Uytterhoeven <geert@...ux-m68k.org> wrote:
>
> > > Can we pull this into driver-core-next please? It fixes issues on some
> > > boards with fw_devlink=on.
> >
> > On r8a77951-salvator-xs.dts, it introduces one more failure:
> >
> >     OF: /soc/i2c@...d8000/gpio@...pcie-sata-switch-hog: could not get
> > #gpio-cells for /cpus/cpu@102

Geert,

One good thing is that it's noticing this being weird and ignoring it
in your particular board. I *think* it interprets the "7" as a phandle
and that's cpu@102 and realizes it's not a gpio-controller. For at
least in your case, it's a safe failure.

> >
> > Seems like it doesn't parse gpios properties in GPIO hogs correctly.
>
> Could it be that the code assumes no self-referencing phandles?
> (Just guessing...)
>

Linus,

Ok I tried to understand what gpio-hogs means. It's not fully clear to
me. But it looks like if a gpio-controller has a gpio-hog, then it
doesn't have/need gpio-cells? Is that right?

So if a gpio-controller has a gpio-hog, can it ever be referred to by
another consumer in DT using blah-gpios = ...? If so, I don't see any
obvious code that's handling the missing gpio-cells in this case.

Long story short, please help me understand gpio-hog in the context of
finding dependencies in DT.

Thanks,
Saravana