linux-kernel - Re: [PATCH v5 4/7] pwm: pca9685: Reset registers to POR state in probe

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Message-ID: <YEDdwzNxPEVK8JHT@workstation.tuxnet>
Date:   Thu, 4 Mar 2021 14:16:51 +0100
From:   Clemens Gruber <clemens.gruber@...ruber.com>
To:     Uwe Kleine-König 
        <u.kleine-koenig@...gutronix.de>
Cc:     linux-pwm@...r.kernel.org,
        Thierry Reding <thierry.reding@...il.com>,
        Sven Van Asbroeck <TheSven73@...il.com>,
        Lee Jones <lee.jones@...aro.org>, linux-kernel@...r.kernel.org,
        Mika Westerberg <mika.westerberg@...ux.intel.com>,
        David Jander <david@...tonic.nl>
Subject: Re: [PATCH v5 4/7] pwm: pca9685: Reset registers to POR state in
 probe

On Mon, Mar 01, 2021 at 10:46:33PM +0100, Uwe Kleine-König wrote:
> Hello Clemens,
> 
> On Tue, Dec 15, 2020 at 10:22:25PM +0100, Clemens Gruber wrote:
> > Reset the prescale and ON/OFF registers to their POR default state in
> > the probe function. Otherwise, the PWMs could still be active after a
> > watchdog reset and reboot, etc.
> 
> My memories are swapped out because it's already so long ago I looked
> into this series. I thought it was already said that taking over the
> configured state in probe is the nice thing to do?!

Yes, but Sven voiced some concerns about the introduced complexities
when removing the resets.

I was torn between the two options.

I think it would be a good idea to first switch to the atomic API while
keeping the resets and then evaluate removing them in a separate patch
series.

Thanks,
Clemens