linux-kernel - [PATCH] USB:fix USB3 devices behind USB3 hubs not resuming at hibernate thaw

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Message-Id: <20180321052942.2853-1-zhengjun.xing@linux.intel.com>
Date:   Wed, 21 Mar 2018 13:29:42 +0800
From:   Zhengjun Xing <zhengjun.xing@...ux.intel.com>
To:     gregkh@...uxfoundation.org
Cc:     stern@...land.harvard.edu, mathias.nyman@...ux.intel.com,
        linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org,
        Zhengjun Xing <zhengjun.xing@...ux.intel.com>
Subject: [PATCH] USB:fix USB3 devices behind USB3 hubs not resuming at hibernate thaw

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.

Signed-off-by: Zhengjun Xing <zhengjun.xing@...ux.intel.com>
---
 drivers/usb/core/generic.c | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/drivers/usb/core/generic.c b/drivers/usb/core/generic.c
index 83c14dda6300..bc8242bc4564 100644
--- a/drivers/usb/core/generic.c
+++ b/drivers/usb/core/generic.c
@@ -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);
-- 
2.11.0