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

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Message-ID: <AM6PR08MB4376058D3FFB4139E9292EE8FFB09@AM6PR08MB4376.eurprd08.prod.outlook.com>
Date:   Mon, 20 Jun 2022 14:18:30 +0000
From:   Pierluigi Passaro <pierluigi.p@...iscite.com>
To:     Andy Shevchenko <andy.shevchenko@...il.com>,
        Alifer Willians de Moraes <alifer.m@...iscite.com>
CC:     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

Hi All,

> > From: FrancescoFerraro <francesco.f@...iscite.com>
> >
> > 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.

> >         const struct pca953x_reg_config *regs;
> > +       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 something like in drivers/gpio/gpio-omap.c ?

> >         ret = regmap_bulk_read(chip->regmap, regaddr, value, NBANK(chip));
> >         if (ret < 0) {
> > -               dev_err(&chip->client->dev, "failed reading register\n");
> > +               if (!chip->is_in_suspend)
> > +                       dev_err(&chip->client->dev, "failed reading register\n");
> Hmm... Maybe we can simply move it to debug level?

On the other side, this can be a serious problem, so I'm not sure the level should be changed. 

> >                 return ret;
> >         }
> ...
> >         chip = devm_kzalloc(&client->dev, sizeof(*chip), GFP_KERNEL);
> >         if (chip == NULL)
> >                 return -ENOMEM;
> > +       chip->is_in_suspend = 0;
> Redundant change.
> -- 
> With Best Regards,
> Andy Shevchenko

Thanks
Best Regards
Pier