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

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Message-ID: <1552994106.14757.34.camel@suse.com>
Date:   Tue, 19 Mar 2019 12:15:06 +0100
From:   Oliver Neukum <oneukum@...e.com>
To:     Johan Hovold <johan@...nel.org>
Cc:     Loic Poulain <loic.poulain@...aro.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Karoly Pados <pados@...os.hu>, linux-kernel@...r.kernel.org,
        linux-usb@...r.kernel.org
Subject: Re: [PATCH v2] USB: serial: cp210x: Fix GPIO in autosuspend

On Di, 2019-03-19 at 11:36 +0100, Johan Hovold wrote:
> On Mon, Feb 18, 2019 at 10:17:12AM +0100, Oliver Neukum wrote:
> > On So, 2019-02-17 at 18:59 +0100, Karoly Pados wrote:
> > > Current GPIO code in cp210x fails to take USB autosuspend into account,
> > > making it practically impossible to use GPIOs with autosuspend enabled
> > > without user configuration. Fix this like for ftdi_sio in a previous patch.
> > > Tested on a CP2102N.
> > your patch is looking good to me, but I am afraid there are issues.
> > How do the GPIO lines on the device interact with USB reset and system
> > suspend?
> 
> What was your concern here, Oliver?

If you have a device resetting or losing power (for reset_resume) the
GPIO lines will revert to the default. But that change is not reported
to user space, is it?
So the original patch is correct, but there are more situations rather
than suspend which could trigger the problem.

	Regards
		Oliver