USB: Implement PM FREEZE and PRETHAW

This patch (as884) finally implements the time-saving semantics
possible with the Power Management FREEZE and PRETHAW events.  Their
proper handling requires only that devices be quiesced, with
interrupts and DMA turned off; non-root USB devices don't actually
need to be put in a suspended state.  The patch checks and avoids
doing the suspend call when possible.

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

1 files changed, 0 insertions, 4 deletions

diff --git a/drivers/usb/core/generic.c b/drivers/usb/core/generic.c
index 9bbcb20e2d94..e7ec9b6b7a93 100644
--- a/drivers/usb/core/generic.c
+++ b/drivers/usb/core/generic.c
@@ -193,10 +193,6 @@ static void generic_disconnect(struct usb_device *udev)
 
 static int generic_suspend(struct usb_device *udev, pm_message_t msg)
 {
-        /* USB devices enter SUSPEND state through their hubs, but can be
-         * marked for FREEZE as soon as their children are already idled.
-         * But those semantics are useless, so we equate the two (sigh).
-         */
         return usb_port_suspend(udev);
 }