linux-kernel - Re: [PATCH v2] USB: serial: cp210x: Fix GPIO in autosuspend

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Message-ID: <20190320091144.GE15782@localhost>
Date:   Wed, 20 Mar 2019 10:11:44 +0100
From:   Johan Hovold <johan@...nel.org>
To:     Karoly Pados <pados@...os.hu>
Cc:     Johan Hovold <johan@...nel.org>, Oliver Neukum <oneukum@...e.com>,
        Loic Poulain <loic.poulain@...aro.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-kernel@...r.kernel.org, linux-usb@...r.kernel.org
Subject: Re: [PATCH v2] USB: serial: cp210x: Fix GPIO in autosuspend

On Tue, Mar 19, 2019 at 05:19:24PM +0000, Karoly Pados wrote:
> >> On Di, 2019-03-19 at 11:36 +0100, Johan Hovold wrote:

> > This patch just added the missing auto-resume handling, but, yeah,
> > there may be devices out there for which things may get out of sync if
> > they lose state over suspend. I think Karoly confirmed this wasn't the
> > case with cp210x.
> 
> The way I tested this is very simple: I just toggled an output pin. If
> the device would lose its state during suspend, then the pin state
> would return to its factory default as soon the it went into suspend.
> Since the LED stayed stable over suspend (I connected an LED), it
> seems these devices don't lose state. I did not, however, test all
> device state in detail to see if every setting remained. I cannot
> vouch for whether *all* state is retained.

I think your test should be sufficient.

Thanks,
Johan