[3.16.y-ckt stable] Patch "usb: core: lpm: set lpm_capable for root hub device" has been added to staging queue

[Luis Henriques]

This is a note to let you know that I have just added a patch titled

    usb: core: lpm: set lpm_capable for root hub device

to the linux-3.16.y-queue branch of the 3.16.y-ckt extended stable tree 
which can be found at:

    http://kernel.ubuntu.com/git/ubuntu/linux.git/log/?h=linux-3.16.y-queue

This patch is scheduled to be released in version 3.16.7-ckt16.

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.16.y-ckt tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Luis

------

>From 6697ad9553bbd57e638586242873833414ee8a08 Mon Sep 17 00:00:00 2001
From: Lu Baolu <baolu.lu at linux.intel.com>
Date: Tue, 16 Jun 2015 09:08:26 +0800
Subject: usb: core: lpm: set lpm_capable for root hub device

commit 2d2a316765d956bc5cb6bb367b2ec52ca59ab8e9 upstream.

Commit 25cd2882e2fc ("usb/xhci: Change how we indicate a host supports
Link PM.") removed the code to set lpm_capable for USB 3.0 super-speed
root hub. The intention of that change was to avoid touching usb core
internal field, a.k.a. lpm_capable, and let usb core to set it by
checking U1 and U2 exit latency values in the descriptor.

Usb core checks and sets lpm_capable in hub_port_init(). Unfortunately,
root hub is a special usb device as it has no parent. Hub_port_init()
will never be called for a root hub device. That means lpm_capable will
by no means be set for the root hub. As the result, lpm isn't functional
at all in Linux kernel.

This patch add the code to check and set lpm_capable when registering a
root hub device. It could be back-ported to kernels as old as v3.15,
that contains the Commit 25cd2882e2fc ("usb/xhci: Change how we indicate
a host supports Link PM.").

Reported-by: Kevin Strasser <kevin.strasser at linux.intel.com>
Signed-off-by: Lu Baolu <baolu.lu at linux.intel.com>
Acked-by: Alan Stern <stern at rowland.harvard.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh at linuxfoundation.org>
Signed-off-by: Luis Henriques <luis.henriques at canonical.com>
---
 drivers/usb/core/hcd.c | 7 +++++--
 drivers/usb/core/hub.c | 2 +-
 drivers/usb/core/usb.h | 1 +
 3 files changed, 7 insertions(+), 3 deletions(-)

diff --git a/drivers/usb/core/hcd.c b/drivers/usb/core/hcd.c
index 4195906f94d6..c4dc63ad580a 100644
--- a/drivers/usb/core/hcd.c
+++ b/drivers/usb/core/hcd.c
@@ -1025,9 +1025,12 @@ static int register_root_hub(struct usb_hcd *hcd)
 				dev_name(&usb_dev->dev), retval);
 		return (retval < 0) ? retval : -EMSGSIZE;
 	}
-	if (usb_dev->speed == USB_SPEED_SUPER) {
+
+	if (le16_to_cpu(usb_dev->descriptor.bcdUSB) >= 0x0201) {
 		retval = usb_get_bos_descriptor(usb_dev);
-		if (retval < 0) {
+		if (!retval) {
+			usb_dev->lpm_capable = usb_device_supports_lpm(usb_dev);
+		} else if (usb_dev->speed == USB_SPEED_SUPER) {
 			mutex_unlock(&usb_bus_list_lock);
 			dev_dbg(parent_dev, "can't read %s bos descriptor %d\n",
 					dev_name(&usb_dev->dev), retval);
diff --git a/drivers/usb/core/hub.c b/drivers/usb/core/hub.c
index a3ab650a1f72..962fdf5c621b 100644
--- a/drivers/usb/core/hub.c
+++ b/drivers/usb/core/hub.c
@@ -126,7 +126,7 @@ struct usb_hub *usb_hub_to_struct_hub(struct usb_device *hdev)
 	return usb_get_intfdata(hdev->actconfig->interface[0]);
 }

-static int usb_device_supports_lpm(struct usb_device *udev)
+int usb_device_supports_lpm(struct usb_device *udev)
 {
 	/* USB 2.1 (and greater) devices indicate LPM support through
 	 * their USB 2.0 Extended Capabilities BOS descriptor.
diff --git a/drivers/usb/core/usb.h b/drivers/usb/core/usb.h
index d9d08720c386..d7ac1603826b 100644
--- a/drivers/usb/core/usb.h
+++ b/drivers/usb/core/usb.h
@@ -65,6 +65,7 @@ extern int  usb_hub_init(void);
 extern void usb_hub_cleanup(void);
 extern int usb_major_init(void);
 extern void usb_major_cleanup(void);
+extern int usb_device_supports_lpm(struct usb_device *udev);

 #ifdef	CONFIG_PM