linux-kernel - [PATCH 1/2] USB: reset-resume the device when PORT

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Date:   Fri,  7 May 2021 17:33:28 +0800
From:   chris.chiu@...onical.com
To:     stern@...land.harvard.edu, gregkh@...uxfoundation.org,
        m.v.b@...box.com, hadess@...ess.net
Cc:     linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org,
        Chris Chiu <chris.chiu@...onical.com>
Subject: [PATCH 1/2] USB: reset-resume the device when PORT_SUSPEND is set but timeout

From: Chris Chiu <chris.chiu@...onical.com>

On the Realtek hub of Dell Dock WD19, the port which has wakeup
enabled descendants will sometimes timeout when setting PORT_SUSPEND
feature. After checking the PORT_SUSPEND bit in wPortStatus, it is
already set. However, the hub will fail to activate because the
PORT_SUSPEND feature of that port is not cleared during resume. All
devices connecting via the port are lost after resume.

This commit force reset-resume the device connected to the timeout
but suspended port so that the hub will have chance to clear the
PORT_SUSPEND feature during resume.

Signed-off-by: Chris Chiu <chris.chiu@...onical.com>
---
 drivers/usb/core/hub.c | 15 +++++++++++++++
 1 file changed, 15 insertions(+)

diff --git a/drivers/usb/core/hub.c b/drivers/usb/core/hub.c
index b2bc4b7c4289..18603949a8de 100644
--- a/drivers/usb/core/hub.c
+++ b/drivers/usb/core/hub.c
@@ -3385,6 +3385,21 @@ int usb_port_suspend(struct usb_device *udev, pm_message_t msg)
 		status = 0;
 	}
 	if (status) {
+		if (status == -ETIMEDOUT) {
+			u16 portstatus, portchange;
+
+			status = hub_port_status(hub, port1, &portstatus,
+					&portchange);
+
+			dev_dbg(&port_dev->dev,
+				"suspend timeout, status %04x\n", portstatus);
+
+			if (status == 0 && port_is_suspended(hub, portstatus)) {
+				udev->reset_resume = 1;
+				goto err_wakeup;
+			}
+		}
+
 		dev_dbg(&port_dev->dev, "can't suspend, status %d\n", status);
 
 		/* Try to enable USB3 LTM again */
-- 
2.20.1