From: Johan Hovold <johan@kernel.org>
To: Oliver Neukum <oneukum@suse.com>
Cc: Johan Hovold <johan@kernel.org>,
Loic Poulain <loic.poulain@linaro.org>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
Karoly Pados <pados@pados.hu>,
linux-kernel@vger.kernel.org, linux-usb@vger.kernel.org
Subject: [v2] USB: serial: cp210x: Fix GPIO in autosuspend
Date: Tue, 19 Mar 2019 14:14:09 +0100 [thread overview]
Message-ID: <20190319131409.GL6124@localhost> (raw)
On Tue, Mar 19, 2019 at 12:15:06PM +0100, Oliver Neukum wrote:
> 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?
This driver doesn't support reset_resume() so that shouldn't be an
issue, right? We'd disconnect (deregister the gpiochip) and re-probe
instead.
> So the original patch is correct, but there are more situations rather
> than suspend which could trigger the problem.
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.
Johan
next reply other threads:[~2019-03-19 13:14 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-03-19 13:14 Johan Hovold [this message]
-- strict thread matches above, loose matches on Subject: below --
2019-03-20 9:11 [v2] USB: serial: cp210x: Fix GPIO in autosuspend Johan Hovold
2019-03-19 17:19 Karoly Pados
2019-03-19 17:12 Karoly Pados
2019-03-19 11:15 Oliver Neukum
2019-03-19 10:36 Johan Hovold
2019-02-20 9:23 Johan Hovold
2019-02-18 9:17 Oliver Neukum
2019-02-17 17:59 Karoly Pados
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20190319131409.GL6124@localhost \
--to=johan@kernel.org \
--cc=gregkh@linuxfoundation.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-usb@vger.kernel.org \
--cc=loic.poulain@linaro.org \
--cc=oneukum@suse.com \
--cc=pados@pados.hu \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).