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Date:   Fri, 29 Sep 2023 14:26:47 +0200
From:   Thierry Reding <thierry.reding@gmail.com>
To:     Luca Ceresoli <luca.ceresoli@bootlin.com>
Cc:     Linus Walleij <linus.walleij@linaro.org>,
        Prathamesh Shete <pshete@nvidia.com>, jonathanh@nvidia.com,
        linux-gpio@vger.kernel.org, linux-tegra@vger.kernel.org,
        linux-kernel@vger.kernel.org
Subject: Re: [PATCH v3] pinctrl: tegra: Add support to display pin function
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On Thu, Sep 28, 2023 at 08:53:19AM +0200, Luca Ceresoli wrote:
> Hello Linus, Prathamesh,
>=20
> On Wed, 27 Sep 2023 10:54:15 +0200
> Linus Walleij <linus.walleij@linaro.org> wrote:
>=20
> > On Mon, Sep 25, 2023 at 6:30=E2=80=AFPM Luca Ceresoli <luca.ceresoli@bo=
otlin.com> wrote:
> >=20
> > > The symptom is that i2c3 is not working anymore, the I2C lines being
> > > always high. No other known issues at the moment. =20
> >=20
> > Hm....
> >=20
> > >> +     {"nvidia,function",             TEGRA_PINCONF_PARAM_FUNCTION},=
 =20
> > >
> > > FYI, I reduced your patch to only this line plus the one in the
> > > pinctrl-tegra.h and the problem appears as well. =20
> >=20
> > I think there is a conflict now, that the pinconf is "stealing" the fun=
ction
> > assignment from the pinmux call.
> >=20
> > It's just a debugprint, I will revert the patch, Luca can investigate a=
nd you
>=20
> Thanks for the quick revert Linus.
>=20
> > can test a new patch then we will merge that.
>=20
> Prathamesh, if you send a new patch it would be great if you can Cc: me s=
o I
> can test it.

I was able to reproduce this on tegra20-trimslice, and it looks indeed
that the "shortcut" of supporting this through the pinconf "framework"
doesn't work. In addition to the pinmux now no longer getting applied
(exactly why that is I don't think I understand), it also leads to weird
things in other parts of the debugfs output. For example the code now
ends up trying to read a u32 from the nvidia,function property, which is
actually a string. That seems to be fine, but obviously it doesn't yield
the value that is expected for a function and messes up the config param
which will then later on fail to properly display.

Anyway, turns out the correct implementation is even shorter. I've sent
out a patch.

Thierry

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