linux-kernel - Re: [PATCH 2/5] usb: typec: ucsi: Check for notifications after init

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Message-ID: <ZgsU3HsfDJzjPCWA@cae.in-ulm.de>
Date: Mon, 1 Apr 2024 22:11:08 +0200
From: "Christian A. Ehrhardt" <lk@...e.de>
To: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
Cc: linux-kernel@...r.kernel.org,
	Heikki Krogerus <heikki.krogerus@...ux.intel.com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Prashant Malani <pmalani@...omium.org>,
	Jameson Thies <jthies@...gle.com>,
	Abhishek Pandit-Subedi <abhishekpandit@...omium.org>,
	Neil Armstrong <neil.armstrong@...aro.org>,
	Uwe Kleine-König <u.kleine-koenig@...gutronix.de>,
	Samuel Čavoj <samuel@...oj.net>,
	linux-usb@...r.kernel.org, Kenneth Crudup <kenny@...ix.com>
Subject: Re: [PATCH 2/5] usb: typec: ucsi: Check for notifications after init


Hi,

On Fri, Mar 29, 2024 at 06:21:08PM +0200, Dmitry Baryshkov wrote:
> On Wed, Mar 20, 2024 at 08:39:23AM +0100, Christian A. Ehrhardt wrote:
> > The completion notification for the final SET_NOTIFICATION_ENABLE
> > command during initialization can include a connector change
> > notification.  However, at the time this completion notification is
> > processed, the ucsi struct is not ready to handle this notification.
> > As a result the notification is ignored and the controller
> > never sends an interrupt again.
> > 
> > Re-check CCI for a pending connector state change after
> > initialization is complete. Adjust the corresponding debug
> > message accordingly.
> > 
> > Fixes: 71a1fa0df2a3 ("usb: typec: ucsi: Store the notification mask")
> > Cc: stable@...r.kernel.org
> > Signed-off-by: Christian A. Ehrhardt <lk@...e.de>
> > ---
> >  drivers/usb/typec/ucsi/ucsi.c | 10 +++++++++-
> >  1 file changed, 9 insertions(+), 1 deletion(-)
> > 
> > diff --git a/drivers/usb/typec/ucsi/ucsi.c b/drivers/usb/typec/ucsi/ucsi.c
> > index 8a6645ffd938..dceeed207569 100644
> > --- a/drivers/usb/typec/ucsi/ucsi.c
> > +++ b/drivers/usb/typec/ucsi/ucsi.c
> > @@ -1237,7 +1237,7 @@ void ucsi_connector_change(struct ucsi *ucsi, u8 num)
> >  	struct ucsi_connector *con = &ucsi->connector[num - 1];
> >  
> >  	if (!(ucsi->ntfy & UCSI_ENABLE_NTFY_CONNECTOR_CHANGE)) {
> > -		dev_dbg(ucsi->dev, "Bogus connector change event\n");
> > +		dev_dbg(ucsi->dev, "Early connector change event\n");
> >  		return;
> >  	}
> >  
> > @@ -1636,6 +1636,7 @@ static int ucsi_init(struct ucsi *ucsi)
> >  {
> >  	struct ucsi_connector *con, *connector;
> >  	u64 command, ntfy;
> > +	u32 cci;
> >  	int ret;
> >  	int i;
> >  
> > @@ -1688,6 +1689,13 @@ static int ucsi_init(struct ucsi *ucsi)
> >  
> >  	ucsi->connector = connector;
> >  	ucsi->ntfy = ntfy;
> > +
> > +	ret = ucsi->ops->read(ucsi, UCSI_CCI, &cci, sizeof(cci));
> > +	if (ret)
> > +		return ret;
> > +	if (UCSI_CCI_CONNECTOR(READ_ONCE(cci)))
> > +		ucsi_connector_change(ucsi, cci);
> > +
> 
> I think this leaves place for the race. With this patchset + "Ack
> connector change early" in place Neil triggered the following backtrace
> on sm8550 HDK while testing my UCSI-qcom-fixes patchset:

Sorry, but this seems to be a brown paper bag change.
- The READ_ONCE is bogus and a remnant of a prevoius verion of the
  change.
- Calling ->read should probably be done with the PPM lock held.
- The argument to ucsi_connector_change() must be
  UCSI_CCI_CONNECTOR(cci) instead of the plain cci.
I'll send a fix.

> What happens:
[ ... ]
> 
> [   10.595807] ------------[ cut here ]------------
> [   10.595808] WARNING: CPU: 6 PID: 101 at kernel/workqueue.c:2384 __queue_work+0x374/0x474
> 
> [skipped the register dump]
> 
> [   10.595953]  __queue_work+0x374/0x474
> [   10.595956]  queue_work_on+0x68/0x84
> [   10.595959]  ucsi_connector_change+0x54/0x88 [typec_ucsi]
> [   10.595963]  ucsi_init_work+0x834/0x85c [typec_ucsi]
> [   10.595968]  process_one_work+0x148/0x29c
> [   10.595971]  worker_thread+0x2fc/0x40c
> [   10.595974]  kthread+0x110/0x114
> [   10.595978]  ret_from_fork+0x10/0x20
> [   10.595985] ---[ end trace 0000000000000000 ]---
> 
> Warning, because the work is already scheduled.

No, the reason is the wrong connector number. Scheduling a work that
is already scheduled is fine.

Best regards
Christian