USB: EHCI: carry out port handover during each root-hub resume

This patch (as1044) causes EHCI port handover for non-high-speed
devices to occur during every root-hub resume, not just in cases where
the controller lost power or was reset.  This is necessary because:

	When some machines go into suspend, they remove power from
	on-board USB devices while retaining suspend current for USB
	controllers.

	The user might well unplug a USB device while the system is
	suspended and then plug it back in before resuming.

A corresponding change is made to the core resume routine; now
high-speed root hubs will always be resumed when the system wakes up,
even if they were suspended before the system went to sleep.  If this
weren't done then EHCI port handover wouldn't work, since it is called
when the EHCI root hub is resumed.

Finally, a comment is added to the hub driver explaining the khubd has
to be freezable; if it weren't frozen then it could interfere with
port handover.

Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

1 files changed, 7 insertions, 2 deletions

diff --git a/drivers/usb/core/driver.c b/drivers/usb/core/driver.c
index 801b6f142fa..ebccdefcc6f 100644
--- a/drivers/usb/core/driver.c
+++ b/drivers/usb/core/driver.c
@@ -1523,9 +1523,14 @@ static int usb_suspend(struct device *dev, pm_message_t message)
         udev = to_usb_device(dev);
 
         /* If udev is already suspended, we can skip this suspend and
-         * we should also skip the upcoming system resume. */
+         * we should also skip the upcoming system resume.  High-speed
+         * root hubs are an exception; they need to resume whenever the
+         * system wakes up in order for USB-PERSIST port handover to work
+         * properly.
+         */
         if (udev->state == USB_STATE_SUSPENDED) {
-                udev->skip_sys_resume = 1;
+                if (udev->parent || udev->speed != USB_SPEED_HIGH)
+                        udev->skip_sys_resume = 1;
                 return 0;
         }