patch "USB:fix USB3 devices behind USB3 hubs not resuming at hibernate thaw" added to usb-testing

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

USB:fix USB3 devices behind USB3 hubs not resuming at hibernate thaw

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-testing 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 be merged to the usb-next branch sometime soon, after it passes testing, and the merge window is open.

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

From: Zhengjun Xing <[email protected]>
Date: Wed, 21 Mar 2018 13:29:42 +0800
Subject: USB:fix USB3 devices behind USB3 hubs not resuming at hibernate thaw
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USB3 hubs don't support global suspend.

USB3 specification 10.10, Enhanced SuperSpeed hubs only support selective suspend and resume, they do not support global suspend/resume where the hub downstream facing ports states are not affected.

When system enters hibernation it first enters freeze process where only the root hub enters suspend, usb_port_suspend() is not called for other devices, and suspend status flags are not set for them. Other devices are expected to suspend globally. Some external USB3 hubs will suspend the downstream facing port at global suspend. These devices won't be resumed at thaw as the suspend status flag is not set.

A USB3 removable hard disk connected through a USB3 hub that won't resume at thaw will fail to synchronize SCSI cache, return “cmd cmplt err -71” error, and needs a 60 seconds timeout which causing system hang for 60s before the USB host reset the port for the USB3 removable hard disk to recover.

Fix this by always calling usb_port_suspend() during freeze for USB3 devices.

---
 drivers/usb/core/generic.c | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

index 83c14dda6300..bc8242bc4564 100644
@@ -210,8 +210,13 @@ static int generic_suspend(struct usb_device *udev, pm_message_t msg)
 	if (!udev->parent)
 		rc = hcd_bus_suspend(udev, msg);
 
-	/* Non-root devices don't need to do anything for FREEZE or PRETHAW */
-	else if (msg.event == PM_EVENT_FREEZE || msg.event == PM_EVENT_PRETHAW)
+	/*
+	 * Non-root USB2 devices don't need to do anything for FREEZE
+	 * or PRETHAW. USB3 devices don't support global suspend and
+	 * needs to be selectively suspended.
+	 */
+	else if ((msg.event == PM_EVENT_FREEZE || msg.event == PM_EVENT_PRETHAW)
+		 && (udev->speed < USB_SPEED_SUPER))
 		rc = 0;
 	else
 		rc = usb_port_suspend(udev, msg);

2.16.2