linux-kernel - Re: [PATCH 04/12] iio: adc: ad9467: fix reset gpio handling

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Message-ID: <CAMknhBGjm2ja9HOenOWi9O5Ao8qUg=gT=_Vz8CyxQ=pfNX2EJQ@mail.gmail.com>
Date:   Fri, 1 Dec 2023 11:01:55 -0600
From:   David Lechner <dlechner@...libre.com>
To:     Nuno Sá <noname.nuno@...il.com>
Cc:     nuno.sa@...log.com, linux-kernel@...r.kernel.org,
        devicetree@...r.kernel.org, linux-iio@...r.kernel.org,
        Olivier MOYSAN <olivier.moysan@...s.st.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        Rob Herring <robh+dt@...nel.org>,
        Frank Rowand <frowand.list@...il.com>,
        Jonathan Cameron <jic23@...nel.org>,
        Lars-Peter Clausen <lars@...afoo.de>,
        Michael Hennerich <Michael.Hennerich@...log.com>
Subject: Re: [PATCH 04/12] iio: adc: ad9467: fix reset gpio handling

On Fri, Dec 1, 2023 at 2:47 AM Nuno Sá <noname.nuno@...il.com> wrote:
>
> On Thu, 2023-11-30 at 15:41 -0600, David Lechner wrote:
> > On Tue, Nov 21, 2023 at 4:17 AM Nuno Sa via B4 Relay
> > <devnull+nuno.sa.analog.com@...nel.org> wrote:
> > >
> > > From: Nuno Sa <nuno.sa@...log.com>
> > >
> > > The reset gpio was being requested with GPIOD_OUT_LOW which means, not
> > > asserted. Then it was being asserted but never de-asserted which means
> > > the devices was left in reset. Fix it by de-asserting the gpio.
> >
> > It could be helpful to update the devicetree bindings to state the
> > expected active-high or active-low setting for this gpio so it is
> > clear which state means asserted.
> >
>
> You could state that the chip is active low but I don't see that change that
> important for now. Not sure if this is clear and maybe that's why your comment.
> GPIOD_OUT_HIGH has nothing to do with active high or low. It just means, "get me the
> pin in the asserted state".
>

I would assume that this bug happened in the first place because
someone forgot GPIOD_OUT_LOW in the devicetree when they were
developing the driver. So this is why I suggested that updating the
devicetree binding docs so that future users are less likely to make
the same mistake. Currently, the bindings don't even have reset-gpios
in the examples.