linux-kernel - [PATCH] usb: typec: ucsi: Clear pending after acking connector change

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Date:   Sat, 15 May 2021 21:09:53 -0700
From:   Bjorn Andersson <bjorn.andersson@...aro.org>
To:     Heikki Krogerus <heikki.krogerus@...ux.intel.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Benjamin Berg <bberg@...hat.com>
Cc:     linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH] 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.

Fixes: 217504a05532 ("usb: typec: ucsi: Work around PPM losing change information")
Signed-off-by: Bjorn Andersson <bjorn.andersson@...aro.org>
---
 drivers/usb/typec/ucsi/ucsi.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/usb/typec/ucsi/ucsi.c b/drivers/usb/typec/ucsi/ucsi.c
index 282c3c825c13..f451ce0132a9 100644
--- a/drivers/usb/typec/ucsi/ucsi.c
+++ b/drivers/usb/typec/ucsi/ucsi.c
@@ -694,8 +694,8 @@ 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;
-- 
2.29.2