tree c79c27a71672d51ed935ca23b8faeb507664a4a9
parent 2b69899934c63b7b9432568584fb4c4a2924f40c
author Sarah Sharp <sarah.a.sharp@linux.intel.com> 1316035492 -0700
committer Greg Kroah-Hartman <gregkh@suse.de> 1316547230 -0700

USB: When hot reset for USB3 fails, try warm reset.

When a hot reset (standard USB port reset) fails on a USB 3.0 port, the
host controller transitions to the "Error" state.  It reports the port
link state as "Inactive", sets the link state change flag, and (if the
device disconnects) also reports the disconnect and connect change status.
It's also supposed to transition the link state to "RxDetect", but the NEC
µPD720200 xHCI host does not.

Unfortunately, Harald found that the combination of the NEC µPD720200 and
a LogiLink USB 3.0 to SATA adapter triggered this issue.  The USB core
would reset the device, the port would go into this error state, and the
device would never be enumerated.  This combination works under Windows,
but not under Linux.

When a hot reset fails on a USB 3.0 port, and the link state is reported
as Inactive, fall back to a warm port reset instead.  Harald confirms that
with a warm port reset (along with all the change bits being correctly
cleared), the USB 3.0 device will successfully enumerate.

Harald also had to add two other patches ("xhci: Set change bit when warm
reset change is set." and "usbcore: refine warm reset logic") to make this
setup work.  Since the warm reset refinement patch is not destined for the
stable kernels (it's too big), this patch should not be backported either.

This fixes https://bugzilla.kernel.org/show_bug.cgi?id=41752

Signed-off-by: Sarah Sharp <sarah.a.sharp@linux.intel.com>
Tested-by: Harald Brennich <harald.brennich@gmx.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>