linux-stable.git/drivers/usb/core, branch v3.2.64 Linux kernel stable tree usb: hub: take hub->hdev reference when processing from eventlist 2014-11-05T20:27:42+00:00 Joe Lawrence joe.lawrence@stratus.com 2014-09-10T19:07:50+00:00 1c20e37c1d0975eca131a6b1d86f3a50d3e4caac commit c605f3cdff53a743f6d875b76956b239deca1272 upstream. During surprise device hotplug removal tests, it was observed that hub_events may try to call usb_lock_device on a device that has already been freed. Protect the usb_device by taking out a reference (under the hub_event_lock) when hub_events pulls it off the list, returning the reference after hub_events is finished using it. Signed-off-by: Joe Lawrence <joe.lawrence@stratus.com> Suggested-by: David Bulkow <david.bulkow@stratus.com> for using kref Suggested-by: Alan Stern <stern@rowland.harvard.edu> for placement Acked-by: Alan Stern <stern@rowland.harvard.edu> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Signed-off-by: Ben Hutchings <ben@decadent.org.uk> 
commit c605f3cdff53a743f6d875b76956b239deca1272 upstream.

During surprise device hotplug removal tests, it was observed that
hub_events may try to call usb_lock_device on a device that has already
been freed. Protect the usb_device by taking out a reference (under the
hub_event_lock) when hub_events pulls it off the list, returning the
reference after hub_events is finished using it.

Signed-off-by: Joe Lawrence <joe.lawrence@stratus.com>
Suggested-by: David Bulkow <david.bulkow@stratus.com> for using kref
Suggested-by: Alan Stern <stern@rowland.harvard.edu> for placement
Acked-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
USB: Fix persist resume of some SS USB devices 2014-09-13T22:41:39+00:00 Pratyush Anand pratyush.anand@st.com 2014-07-18T07:07:10+00:00 7a0d07fbdf86ab3800ba7d8919d083040d156b30 commit a40178b2fa6ad87670fb1e5fa4024db00c149629 upstream. Problem Summary: Problem has been observed generally with PM states where VBUS goes off during suspend. There are some SS USB devices which take longer time for link training compared to many others. Such devices fail to reconnect with same old address which was associated with it before suspend. When system resumes, at some point of time (dpm_run_callback-> usb_dev_resume->usb_resume->usb_resume_both->usb_resume_device-> usb_port_resume) SW reads hub status. If device is present, then it finishes port resume and re-enumerates device with same address. If device is not present then, SW thinks that device was removed during suspend and therefore does logical disconnection and removes all the resource allocated for this device. Now, if I put sufficient delay just before root hub status read in usb_resume_device then, SW sees always that device is present. In normal course(without any delay) SW sees that no device is present and then SW removes all resource associated with the device at this port. In the latter case, after sometime, device says that hey I am here, now host enumerates it, but with new address. Problem had been reproduced when I connect verbatim USB3.0 hard disc with my STiH407 XHCI host running with 3.10 kernel. I see that similar problem has been reported here. https://bugzilla.kernel.org/show_bug.cgi?id=53211 Reading above it seems that bug was not in 3.6.6 and was present in 3.8 and again it was not present for some in 3.12.6, while it was present for few others. I tested with 3.13-FC19 running at i686 desktop, problem was still there. However, I was failed to reproduce it with 3.16-RC4 running at same i686 machine. I would say it is just a random observation. Problem for few devices is always there, as I am unable to find a proper fix for the issue. So, now question is what should be the amount of delay so that host is always able to recognize suspended device after resume. XHCI specs 4.19.4 says that when Link training is successful, port sets CSC bit to 1. So if SW reads port status before successful link training, then it will not find device to be present. USB Analyzer log with such buggy devices show that in some cases device switch on the RX termination after long delay of host enabling the VBUS. In few other cases it has been seen that device fails to negotiate link training in first attempt. It has been reported till now that few devices take as long as 2000 ms to train the link after host enabling its VBUS and RX termination. This patch implements a 2000 ms timeout for CSC bit to set ie for link training. If in a case link trains before timeout, loop will exit earlier. This patch implements above delay, but only for SS device and when persist is enabled. So, for the good device overhead is almost none. While for the bad devices penalty could be the time which it take for link training. But, If a device was connected before suspend, and was removed while system was asleep, then the penalty would be the timeout ie 2000 ms. Results: Verbatim USB SS hard disk connected with STiH407 USB host running 3.10 Kernel resumes in 461 msecs without this patch, but hard disk is assigned a new device address. Same system resumes in 790 msecs with this patch, but with old device address. Signed-off-by: Pratyush Anand <pratyush.anand@st.com> Acked-by: Alan Stern <stern@rowland.harvard.edu> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Signed-off-by: Ben Hutchings <ben@decadent.org.uk> 
commit a40178b2fa6ad87670fb1e5fa4024db00c149629 upstream.

Problem Summary: Problem has been observed generally with PM states
where VBUS goes off during suspend. There are some SS USB devices which
take longer time for link training compared to many others.  Such
devices fail to reconnect with same old address which was associated
with it before suspend.

When system resumes, at some point of time (dpm_run_callback->
usb_dev_resume->usb_resume->usb_resume_both->usb_resume_device->
usb_port_resume) SW reads hub status. If device is present,
then it finishes port resume and re-enumerates device with same
address. If device is not present then, SW thinks that device was
removed during suspend and therefore does logical disconnection
and removes all the resource allocated for this device.

Now, if I put sufficient delay just before root hub status read in
usb_resume_device then, SW sees always that device is present. In normal
course(without any delay) SW sees that no device is present and then SW
removes all resource associated with the device at this port.  In the
latter case, after sometime, device says that hey I am here, now host
enumerates it, but with new address.

Problem had been reproduced when I connect verbatim USB3.0 hard disc
with my STiH407 XHCI host running with 3.10 kernel.

I see that similar problem has been reported here.
https://bugzilla.kernel.org/show_bug.cgi?id=53211
Reading above it seems that bug was not in 3.6.6 and was present in 3.8
and again it was not present for some in 3.12.6, while it was present
for few others. I tested with 3.13-FC19 running at i686 desktop, problem
was still there. However, I was failed to reproduce it with 3.16-RC4
running at same i686 machine. I would say it is just a random
observation. Problem for few devices is always there, as I am unable to
find a proper fix for the issue.

So, now question is what should be the amount of delay so that host is
always able to recognize suspended device after resume.

XHCI specs 4.19.4 says that when Link training is successful, port sets
CSC bit to 1. So if SW reads port status before successful link
training, then it will not find device to be present.  USB Analyzer log
with such buggy devices show that in some cases device switch on the
RX termination after long delay of host enabling the VBUS. In few other
cases it has been seen that device fails to negotiate link training in
first attempt. It has been reported till now that few devices take as
long as 2000 ms to train the link after host enabling its VBUS and
RX termination. This patch implements a 2000 ms timeout for CSC bit to set
ie for link training. If in a case link trains before timeout, loop will
exit earlier.

This patch implements above delay, but only for SS device and when
persist is enabled.

So, for the good device overhead is almost none. While for the bad
devices penalty could be the time which it take for link training.
But, If a device was connected before suspend, and was removed
while system was asleep, then the penalty would be the timeout ie
2000 ms.

Results:

Verbatim USB SS hard disk connected with STiH407 USB host running 3.10
Kernel resumes in 461 msecs without this patch, but hard disk is
assigned a new device address. Same system resumes in 790 msecs with
this patch, but with old device address.

Signed-off-by: Pratyush Anand <pratyush.anand@st.com>
Acked-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
usbcore: don't log on consecutive debounce failures of the same port 2014-09-13T22:41:38+00:00 Oliver Neukum oneukum@suse.de 2014-07-14T13:39:49+00:00 9b627762dee539bbd63b6d1be8f0242741325a27 commit 5ee0f803cc3a0738a63288e4a2f453c85889fbda upstream. Some laptops have an internal port for a BT device which picks up noise when the kill switch is used, but not enough to trigger printk_rlimit(). So we shouldn't log consecutive faults of this kind. Signed-off-by: Oliver Neukum <oneukum@suse.de> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> [bwh: Backported to 3.2: - Adjust context - Error message already includes the port number] Signed-off-by: Ben Hutchings <ben@decadent.org.uk> 
commit 5ee0f803cc3a0738a63288e4a2f453c85889fbda upstream.

Some laptops have an internal port for a BT device which picks
up noise when the kill switch is used, but not enough to trigger
printk_rlimit(). So we shouldn't log consecutive faults of this kind.

Signed-off-by: Oliver Neukum <oneukum@suse.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
[bwh: Backported to 3.2:
 - Adjust context
 - Error message already includes the port number]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
usb: Check if port status is equal to RxDetect 2014-08-06T17:07:38+00:00 Gavin Guo gavin.guo@canonical.com 2014-07-17T17:12:13+00:00 2359626516f1c86af1ab78a835e3c84d04a5c0db commit bb86cf569bbd7ad4dce581a37c7fbd748057e9dc upstream. When using USB 3.0 pen drive with the [AMD] FCH USB XHCI Controller [1022:7814], the second hotplugging will experience the USB 3.0 pen drive is recognized as high-speed device. After bisecting the kernel, I found the commit number 41e7e056cdc662f704fa9262e5c6e213b4ab45dd (USB: Allow USB 3.0 ports to be disabled.) causes the bug. After doing some experiments, the bug can be fixed by avoiding executing the function hub_usb3_port_disable(). Because the port status with [AMD] FCH USB XHCI Controlleris [1022:7814] is already in RxDetect (I tried printing out the port status before setting to Disabled state), it's reasonable to check the port status before really executing hub_usb3_port_disable(). Fixes: 41e7e056cdc6 (USB: Allow USB 3.0 ports to be disabled.) Signed-off-by: Gavin Guo <gavin.guo@canonical.com> Acked-by: Alan Stern <stern@rowland.harvard.edu> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> [bwh: Backported to 3.2: use hub device as context for dev_dbg(), as hub ports are not devices in their own right] Signed-off-by: Ben Hutchings <ben@decadent.org.uk> 
commit bb86cf569bbd7ad4dce581a37c7fbd748057e9dc upstream.

When using USB 3.0 pen drive with the [AMD] FCH USB XHCI Controller
[1022:7814], the second hotplugging will experience the USB 3.0 pen
drive is recognized as high-speed device. After bisecting the kernel,
I found the commit number 41e7e056cdc662f704fa9262e5c6e213b4ab45dd
(USB: Allow USB 3.0 ports to be disabled.) causes the bug. After doing
some experiments, the bug can be fixed by avoiding executing the function
hub_usb3_port_disable(). Because the port status with [AMD] FCH USB
XHCI Controlleris [1022:7814] is already in RxDetect
(I tried printing out the port status before setting to Disabled state),
it's reasonable to check the port status before really executing
hub_usb3_port_disable().

Fixes: 41e7e056cdc6 (USB: Allow USB 3.0 ports to be disabled.)
Signed-off-by: Gavin Guo <gavin.guo@canonical.com>
Acked-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
[bwh: Backported to 3.2: use hub device as context for dev_dbg(),
 as hub ports are not devices in their own right]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
USB: Avoid runtime suspend loops for HCDs that can't handle suspend/resume 2014-07-11T12:33:36+00:00 Alan Stern stern@rowland.harvard.edu 2014-05-23T14:45:54+00:00 502c1d6c3e8bbf4fd9152348ee65c439f37596b8 commit 8ef42ddd9a53b73e6fc3934278710c27f80f324f upstream. Not all host controller drivers have bus-suspend and bus-resume methods. When one doesn't, it will cause problems if runtime PM is enabled in the kernel. The PM core will attempt to suspend the controller's root hub, the suspend will fail because there is no bus-suspend routine, and a -EBUSY error code will be returned to the PM core. This will cause the suspend attempt to be repeated shortly thereafter, in a never-ending loop. Part of the problem is that the original error code -ENOENT gets changed to -EBUSY in usb_runtime_suspend(), on the grounds that the PM core will interpret -ENOENT as meaning that the root hub has gotten into a runtime-PM error state. While this change is appropriate for real USB devices, it's not such a good idea for a root hub. In fact, considering the root hub to be in a runtime-PM error state would not be far from the truth. Therefore this patch updates usb_runtime_suspend() so that it adjusts error codes only for non-root-hub devices. Furthermore, the patch attempts to prevent the problem from occurring in the first place by not enabling runtime PM by default for root hubs whose host controller driver doesn't have bus_suspend and bus_resume methods. Signed-off-by: Alan Stern <stern@rowland.harvard.edu> Reported-by: Will Deacon <will.deacon@arm.com> Tested-by: Will Deacon <will.deacon@arm.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> [bwh: Backported to 3.2: runtime PM is also not supported for USB 3.0 non-root hubs] Signed-off-by: Ben Hutchings <ben@decadent.org.uk> 
commit 8ef42ddd9a53b73e6fc3934278710c27f80f324f upstream.

Not all host controller drivers have bus-suspend and bus-resume
methods.  When one doesn't, it will cause problems if runtime PM is
enabled in the kernel.  The PM core will attempt to suspend the
controller's root hub, the suspend will fail because there is no
bus-suspend routine, and a -EBUSY error code will be returned to the
PM core.  This will cause the suspend attempt to be repeated shortly
thereafter, in a never-ending loop.

Part of the problem is that the original error code -ENOENT gets
changed to -EBUSY in usb_runtime_suspend(), on the grounds that the PM
core will interpret -ENOENT as meaning that the root hub has gotten
into a runtime-PM error state.  While this change is appropriate for
real USB devices, it's not such a good idea for a root hub.  In fact,
considering the root hub to be in a runtime-PM error state would not
be far from the truth.  Therefore this patch updates
usb_runtime_suspend() so that it adjusts error codes only for
non-root-hub devices.

Furthermore, the patch attempts to prevent the problem from occurring
in the first place by not enabling runtime PM by default for root hubs
whose host controller driver doesn't have bus_suspend and bus_resume
methods.

Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Reported-by: Will Deacon <will.deacon@arm.com>
Tested-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
[bwh: Backported to 3.2: runtime PM is also not supported for USB 3.0
 non-root hubs]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
usb: Make DELAY_INIT quirk wait 100ms between Get Configuration requests 2014-04-01T23:58:58+00:00 Julius Werner jwerner@chromium.org 2014-03-04T19:27:38+00:00 3e2ac237de6938d922bb865ba3aeb01d357d6e6e commit d86db25e53fa69e3e97f3b55dd82a70689787c5d upstream. The DELAY_INIT quirk only reduces the frequency of enumeration failures with the Logitech HD Pro C920 and C930e webcams, but does not quite eliminate them. We have found that adding a delay of 100ms between the first and second Get Configuration request makes the device enumerate perfectly reliable even after several weeks of extensive testing. The reasons for that are anyone's guess, but since the DELAY_INIT quirk already delays enumeration by a whole second, wating for another 10th of that isn't really a big deal for the one other device that uses it, and it will resolve the problems with these webcams. Signed-off-by: Julius Werner <jwerner@chromium.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Signed-off-by: Ben Hutchings <ben@decadent.org.uk> 
commit d86db25e53fa69e3e97f3b55dd82a70689787c5d upstream.

The DELAY_INIT quirk only reduces the frequency of enumeration failures
with the Logitech HD Pro C920 and C930e webcams, but does not quite
eliminate them. We have found that adding a delay of 100ms between the
first and second Get Configuration request makes the device enumerate
perfectly reliable even after several weeks of extensive testing. The
reasons for that are anyone's guess, but since the DELAY_INIT quirk
already delays enumeration by a whole second, wating for another 10th of
that isn't really a big deal for the one other device that uses it, and
it will resolve the problems with these webcams.

Signed-off-by: Julius Werner <jwerner@chromium.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
usb: Add device quirk for Logitech HD Pro Webcams C920 and C930e 2014-04-01T23:58:58+00:00 Julius Werner jwerner@chromium.org 2014-03-04T18:52:39+00:00 e226584b8f1fb2499b5e884afccff2afcd49f264 commit e0429362ab15c46ea4d64c3f8c9e0933e48a143a upstream. We've encountered a rare issue when enumerating two Logitech webcams after a reboot that doesn't power cycle the USB ports. They are spewing random data (possibly some leftover UVC buffers) on the second (full-sized) Get Configuration request of the enumeration phase. Since the data is random this can potentially cause all kinds of odd behavior, and since it occasionally happens multiple times (after the kernel issues another reset due to the garbled configuration descriptor), it is not always recoverable. Set the USB_DELAY_INIT quirk that seems to work around the issue. Signed-off-by: Julius Werner <jwerner@chromium.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Signed-off-by: Ben Hutchings <ben@decadent.org.uk> 
commit e0429362ab15c46ea4d64c3f8c9e0933e48a143a upstream.

We've encountered a rare issue when enumerating two Logitech webcams
after a reboot that doesn't power cycle the USB ports. They are spewing
random data (possibly some leftover UVC buffers) on the second
(full-sized) Get Configuration request of the enumeration phase. Since
the data is random this can potentially cause all kinds of odd behavior,
and since it occasionally happens multiple times (after the kernel
issues another reset due to the garbled configuration descriptor), it is
not always recoverable. Set the USB_DELAY_INIT quirk that seems to work
around the issue.

Signed-off-by: Julius Werner <jwerner@chromium.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
usb: hub: Use correct reset for wedged USB3 devices that are NOTATTACHED 2014-01-03T04:33:29+00:00 Julius Werner jwerner@chromium.org 2013-11-07T18:59:14+00:00 871d7214744f86b8edcc7b7d5dc7d4ff1f26d7bd commit 2d51f3cd11f414c56a87dc018196b85fd50b04a4 upstream. This patch adds a check for USB_STATE_NOTATTACHED to the hub_port_warm_reset_required() workaround for ports that end up in Compliance Mode in hub_events() when trying to decide which reset function to use. Trying to call usb_reset_device() with a NOTATTACHED device will just fail and leave the port broken. Signed-off-by: Julius Werner <jwerner@chromium.org> Acked-by: Alan Stern <stern@rowland.harvard.edu> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Signed-off-by: Ben Hutchings <ben@decadent.org.uk> 
commit 2d51f3cd11f414c56a87dc018196b85fd50b04a4 upstream.

This patch adds a check for USB_STATE_NOTATTACHED to the
hub_port_warm_reset_required() workaround for ports that end up in
Compliance Mode in hub_events() when trying to decide which reset
function to use. Trying to call usb_reset_device() with a NOTATTACHED
device will just fail and leave the port broken.

Signed-off-by: Julius Werner <jwerner@chromium.org>
Acked-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
usb: hub: Clear Port Reset Change during init/resume 2014-01-03T04:33:14+00:00 Julius Werner jwerner@chromium.org 2013-10-16T00:45:00+00:00 40c8b4ee658b72eb8c4627c0620a5bb44427d869 commit e92aee330837e4911553761490a8fb843f2053a6 upstream. This patch adds the Port Reset Change flag to the set of bits that are preemptively cleared on init/resume of a hub. In theory this bit should never be set unexpectedly... in practice it can still happen if BIOS, SMM or ACPI code plays around with USB devices without cleaning up correctly. This is especially dangerous for XHCI root hubs, which don't generate any more Port Status Change Events until all change bits are cleared, so this is a good precaution to have (similar to how it's already done for the Warm Port Reset Change flag). Signed-off-by: Julius Werner <jwerner@chromium.org> Acked-by: Alan Stern <stern@rowland.harvard.edu> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> [bwh: Backported to 3.2: - Adjust context - s/usb_clear_port_feature/clear_port_feature/] Signed-off-by: Ben Hutchings <ben@decadent.org.uk> 
commit e92aee330837e4911553761490a8fb843f2053a6 upstream.

This patch adds the Port Reset Change flag to the set of bits that are
preemptively cleared on init/resume of a hub. In theory this bit should
never be set unexpectedly... in practice it can still happen if BIOS,
SMM or ACPI code plays around with USB devices without cleaning up
correctly. This is especially dangerous for XHCI root hubs, which don't
generate any more Port Status Change Events until all change bits are
cleared, so this is a good precaution to have (similar to how it's
already done for the Warm Port Reset Change flag).

Signed-off-by: Julius Werner <jwerner@chromium.org>
Acked-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
[bwh: Backported to 3.2:
 - Adjust context
 - s/usb_clear_port_feature/clear_port_feature/]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
usb: Disable USB 2.0 Link PM before device reset. 2014-01-03T04:33:14+00:00 Sarah Sharp sarah.a.sharp@linux.intel.com 2013-09-30T14:26:29+00:00 7e6337b694966dd7d3b9d904c830b48a4e6a80a6 commit dcc01c0864823f91c3bf3ffca6613e2351702b87 upstream. Before the USB core resets a device, we need to disable the L1 timeout for the roothub, if USB 2.0 Link PM is enabled. Otherwise the port may transition into L1 in between descriptor fetches, before we know if the USB device descriptors changed. LPM will be re-enabled after the full device descriptors are fetched, and we can confirm the device still supports USB 2.0 LPM after the reset. We don't need to wait for the USB device to exit L1 before resetting the device, since the xHCI roothub port diagrams show a transition to the Reset state from any of the Ux states (see Figure 34 in the 2012-08-14 xHCI specification update). This patch should be backported to kernels as old as 3.2, that contain the commit 65580b4321eb36f16ae8b5987bfa1bb948fc5112 "xHCI: set USB2 hardware LPM". That was the first commit to enable USB 2.0 hardware-driven Link Power Management. Signed-off-by: Sarah Sharp <sarah.a.sharp@linux.intel.com> [bwh: Backported to 3.2: adjust context] Signed-off-by: Ben Hutchings <ben@decadent.org.uk> 
commit dcc01c0864823f91c3bf3ffca6613e2351702b87 upstream.

Before the USB core resets a device, we need to disable the L1 timeout
for the roothub, if USB 2.0 Link PM is enabled.  Otherwise the port may
transition into L1 in between descriptor fetches, before we know if the
USB device descriptors changed.  LPM will be re-enabled after the
full device descriptors are fetched, and we can confirm the device still
supports USB 2.0 LPM after the reset.

We don't need to wait for the USB device to exit L1 before resetting the
device, since the xHCI roothub port diagrams show a transition to the
Reset state from any of the Ux states (see Figure 34 in the 2012-08-14
xHCI specification update).

This patch should be backported to kernels as old as 3.2, that contain
the commit 65580b4321eb36f16ae8b5987bfa1bb948fc5112 "xHCI: set USB2
hardware LPM".  That was the first commit to enable USB 2.0
hardware-driven Link Power Management.

Signed-off-by: Sarah Sharp <sarah.a.sharp@linux.intel.com>
[bwh: Backported to 3.2: adjust context]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>