linux-kernel - Re: [PATCH] driver: pca953x: avoid error message when resuming

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Message-ID: <CAHp75VdDDhMgQ_oiHGA1m8TQmP+F6neT_KG=UKqsEe9P96HbHw@mail.gmail.com>
Date:   Mon, 20 Jun 2022 18:02:34 +0200
From:   Andy Shevchenko <andy.shevchenko@...il.com>
To:     Pierluigi Passaro <pierluigi.p@...iscite.com>,
        Wolfram Sang <wsa@...nel.org>
Cc:     Alifer Willians de Moraes <alifer.m@...iscite.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Bartosz Golaszewski <brgl@...ev.pl>,
        Eran Matityahu <eran.m@...iscite.com>,
        Linus Walleij <linus.walleij@...aro.org>,
        "open list:GPIO SUBSYSTEM" <linux-gpio@...r.kernel.org>,
        Francesco Ferraro <francesco.f@...iscite.com>
Subject: Re: [PATCH] driver: pca953x: avoid error message when resuming

On Mon, Jun 20, 2022 at 4:18 PM Pierluigi Passaro
<pierluigi.p@...iscite.com> wrote:

...

> > > Avoids the error messages "pca953x 1-0020: failed reading register"
> > > when resuming from suspend using gpio-key attached to pca9534.
> > Thanks for your report and fix. My comments below.
> > First of all, how many of them do you get and why is it a problem?
>
> The number of occurrences depends on the time required to I2C bus to fully wake-up.
> It's not a real problem, but the message may lead to think about a real I2C problem.

Wolfram, do we have any mechanisms that guarantees that I2C traffic is
not going on a semi-woken up host controller?

Writing this, I'm in doubt this patch is a fix we want. Wouldn't it
just hide the real issue with some resume ordering?

...

> > > +       int is_in_suspend;
> > Usually we call it is_suspended or so, check existing code by `git
> > grep ...`. And it can be boolean.
>
> Do you mean soomething like in drivers/gpio/gpio-omap.c ?

I believe almost any from the list `git grep -nl -w is_suspended` will suffice.

-- 
With Best Regards,
Andy Shevchenko