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

Dmitry Baryshkov
2024-03-29T16:21:12Z

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@vger.kernel.org
> Signed-off-by: Christian A. Ehrhardt <lk@c--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
>