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

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Date: Fri, 29 Mar 2024 18:21:08 +0200
From: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
To: "Christian A. Ehrhardt" <lk@...e.de>
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

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:
What happens:

[   10.421640] write: 00000000: 05 00 e7 db 00 00 00 00

SET_NOTIFICATION_ENABLE

[   10.432359] read: 00000000: 10 01 00 00 00 00 00 80 00 00 00 00 00 00 00 00
[   10.469553] read: 00000010: 04 58 29 20 00 00 00 00 00 00 00 00 00 03 30 01
[   10.476783] read: 00000020: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
[   10.489552] notify: 00000000: 00 00 00 80

COMMAND_COMPLETE

[   10.494194] read: 00000000: 10 01 00 00 00 00 00 80 00 00 00 00 00 00 00 00
[   10.501370] read: 00000010: 04 58 29 20 00 00 00 00 00 00 00 00 00 03 30 01
[   10.508578] read: 00000020: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
[   10.515757] write: 00000000: 04 00 02 00 00 00 00 00

ACK_CC_CI(command completed)

[   10.521100] read: 00000000: 10 01 00 00 00 00 00 20 00 00 00 00 00 00 00 00
[   10.528363] read: 00000010: 04 58 29 20 00 00 00 00 00 00 00 00 00 03 30 01
[   10.535603] read: 00000020: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
[   10.549549] notify: 00000000: 00 00 00 20

ACK_COMPLETE

[Here ucsi->connector and ucsi->ntfy are being set by ucsi_init()

[   10.566654] read: 00000010: 04 58 29 20 00 00 00 00 00 00 00 00 00 03 30 01
[   10.593553] notify: 00000000: 02 00 00 20

Event with CONNECTION_CHANGE. It also schedules connector_change work,
because ucsi->ntfy is already set

[   10.595796] read: 00000000: 10 01 00 00 02 00 00 20 00 00 00 00 00 00 00 00
[   10.595798] read: 00000010: 04 58 29 20 00 00 00 00 00 00 00 00 00 03 30 01
[   10.595799] read: 00000020: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00

The CCI read coming from ucsi_init()

[   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.


>  	return 0;
>  
>  err_unregister:
> -- 
> 2.40.1
>