USB: add missing delay during remote wakeup

This patch (as1330) fixes a bug in khbud's handling of remote
wakeups.  When a device sends a remote-wakeup request, the parent hub
(or the host controller driver, for directly attached devices) begins
the resume sequence and notifies khubd when the sequence finishes.  At
this point the port's SUSPEND feature is automatically turned off.

However the device needs an additional 10-ms resume-recovery time
(TRSMRCY in the USB spec).  Khubd does not wait for this delay if the
SUSPEND feature is off, and as a result some devices fail to behave
properly following a remote wakeup.  This patch adds the missing
delay to the remote-wakeup path.

It also extends the resume-signalling delay used by ehci-hcd and
uhci-hcd from 20 ms (the value in the spec) to 25 ms (the value we use
for non-remote-wakeup resumes).  The extra time appears to help some
devices.

Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Cc: stable <stable@kernel.org>
Cc: Rickard Bellini <rickard.bellini@ericsson.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

1 files changed, 3 insertions, 2 deletions

diff --git a/drivers/usb/host/ehci-hcd.c b/drivers/usb/host/ehci-hcd.c
index 5859522d6edd..1ec3857f22e6 100644
--- a/drivers/usb/host/ehci-hcd.c
+++ b/drivers/usb/host/ehci-hcd.c
@@ -787,9 +787,10 @@ static irqreturn_t ehci_irq (struct usb_hcd *hcd)
 
                         /* start 20 msec resume signaling from this port,
                          * and make khubd collect PORT_STAT_C_SUSPEND to
-                         * stop that signaling.
+                         * stop that signaling.  Use 5 ms extra for safety,
+                         * like usb_port_resume() does.
                          */
-                        ehci->reset_done [i] = jiffies + msecs_to_jiffies (20);
+                        ehci->reset_done[i] = jiffies + msecs_to_jiffies(25);
                         ehci_dbg (ehci, "port %d remote wakeup\n", i + 1);
                         mod_timer(&hcd->rh_timer, ehci->reset_done[i]);
                 }