patch "usb: typec: ucsi: Clear pending after acking connector change" added to usb-linus

This is a note to let you know that I've just added the patch titled

usb: typec: ucsi: Clear pending after acking connector change

to my usb git tree which can be found at
git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/usb.git
in the usb-linus branch.

The patch will show up in the next release of the linux-next tree (usually sometime within the next 24 hours during the week.)

The patch will hopefully also be merged in Linus's tree for the next -rc kernel release.

If you have any questions about this process, please let me know.

From 8c9b3caab3ac26db1da00b8117901640c55a69dd Mon Sep 17 00:00:00 2001
From: Bjorn Andersson <[email protected]>
Date: Sat, 15 May 2021 21:09:53 -0700
Subject: usb: typec: ucsi: Clear pending after acking connector change

It's possible that the interrupt handler for the UCSI driver signals a connector changes after the handler clears the PENDING bit, but before it has sent the acknowledge request. The result is that the handler is invoked yet again, to ack the same connector change.

At least some versions of the Qualcomm UCSI firmware will not handle the second - "spurious" - acknowledgment gracefully. So make sure to not clear the pending flag until the change is acknowledged.

Any connector changes coming in after the acknowledgment, that would have the pending flag incorrectly cleared, would afaict be covered by the subsequent connector status check.

---
 drivers/usb/typec/ucsi/ucsi.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

index 1d8b7df59ff4..b433169ef6fa 100644
@@ -717,8 +717,8 @@ static void ucsi_handle_connector_change(struct work_struct *work)
 	ucsi_send_command(con->ucsi, command, NULL, 0);
 
 	/* 3. ACK connector change */
-	clear_bit(EVENT_PENDING, &ucsi->flags);
 	ret = ucsi_acknowledge_connector_change(ucsi);
+	clear_bit(EVENT_PENDING, &ucsi->flags);
 	if (ret) {
 		dev_err(ucsi->dev, "%s: ACK failed (%d)", __func__, ret);
 		goto out_unlock;

2.31.1