USB: Disable USB 3.0 LPM in critical sections.

There are several places where the USB core needs to disable USB 3.0
Link PM:
 - usb_bind_interface
 - usb_unbind_interface
 - usb_driver_claim_interface
 - usb_port_suspend/usb_port_resume
 - usb_reset_and_verify_device
 - usb_set_interface
 - usb_reset_configuration
 - usb_set_configuration

Use the new LPM disable/enable functions to temporarily disable LPM
around these critical sections.

We need to protect the critical section around binding and unbinding USB
interface drivers.  USB drivers may want to disable hub-initiated USB
3.0 LPM, which will change the value of the U1/U2 timeouts that the xHCI
driver will install.  We need to disable LPM completely until the driver
is bound to the interface, and the driver has a chance to enable
whatever alternate interface setting it needs in its probe routine.
Then re-enable USB3 LPM, and recalculate the U1/U2 timeout values.

We also need to disable LPM in usb_driver_claim_interface,
because drivers like usbfs can bind to an interface through that
function.  Note, there is no way currently for userspace drivers to
disable hub-initiated USB 3.0 LPM.  Revisit this later.

When a driver is unbound, the U1/U2 timeouts may change because we are
unbinding the last driver that needed hub-initiated USB 3.0 LPM to be
disabled.

USB LPM must be disabled when a USB device is going to be suspended.
The USB 3.0 spec does not define a state transition from U1 or U2 into
U3, so we need to bring the device into U0 by disabling LPM before we
can place it into U3.  Therefore, call usb_unlocked_disable_lpm() in
usb_port_suspend(), and call usb_unlocked_enable_lpm() in
usb_port_resume().  If the port suspend fails, make sure to re-enable
LPM by calling usb_unlocked_enable_lpm(), since usb_port_resume() will
not be called on a failed port suspend.

USB 3.0 devices lose their USB 3.0 LPM settings (including whether USB
device-initiated LPM is enabled) across device suspend.  Therefore,
disable LPM before the device will be reset in
usb_reset_and_verify_device(), and re-enable LPM after the reset is
complete and the configuration/alt settings are re-installed.

The calculated U1/U2 timeout values are heavily dependent on what USB
device endpoints are currently enabled.  When any of the enabled
endpoints on the device might change, due to a new configuration, or new
alternate interface setting, we need to first disable USB 3.0 LPM, add
or delete endpoints from the xHCI schedule, install the new interfaces
and alt settings, and then re-enable LPM.  Do this in usb_set_interface,
usb_reset_configuration, and usb_set_configuration.

Basically, there is a call to disable and then enable LPM in all
functions that lock the bandwidth_mutex.  One exception is
usb_disable_device, because the device is disconnecting or otherwise
going away, and we should not care about whether USB 3.0 LPM is enabled.

Signed-off-by: Sarah Sharp <sarah.a.sharp@linux.intel.com>

1 files changed, 53 insertions, 1 deletions

diff --git a/drivers/usb/core/driver.c b/drivers/usb/core/driver.c
index f6f81c85c5cf..f536aebc958e 100644
--- a/drivers/usb/core/driver.c
+++ b/drivers/usb/core/driver.c
@@ -288,6 +288,7 @@ static int usb_probe_interface(struct device *dev)
 	struct usb_device *udev = interface_to_usbdev(intf);
 	const struct usb_device_id *id;
 	int error = -ENODEV;
+	int lpm_disable_error;
 
 	dev_dbg(dev, "%s\n", __func__);
 
@@ -324,6 +325,25 @@ static int usb_probe_interface(struct device *dev)
 	if (driver->supports_autosuspend)
 		pm_runtime_enable(dev);
 
+	/* If the new driver doesn't allow hub-initiated LPM, and we can't
+	 * disable hub-initiated LPM, then fail the probe.
+	 *
+	 * Otherwise, leaving LPM enabled should be harmless, because the
+	 * endpoint intervals should remain the same, and the U1/U2 timeouts
+	 * should remain the same.
+	 *
+	 * If we need to install alt setting 0 before probe, or another alt
+	 * setting during probe, that should also be fine.  usb_set_interface()
+	 * will attempt to disable LPM, and fail if it can't disable it.
+	 */
+	lpm_disable_error = usb_unlocked_disable_lpm(udev);
+	if (lpm_disable_error && driver->disable_hub_initiated_lpm) {
+		dev_err(&intf->dev, "%s Failed to disable LPM for driver %s\n.",
+				__func__, driver->name);
+		error = lpm_disable_error;
+		goto err;
+	}
+
 	/* Carry out a deferred switch to altsetting 0 */
 	if (intf->needs_altsetting0) {
 		error = usb_set_interface(udev, intf->altsetting[0].
@@ -338,6 +358,11 @@ static int usb_probe_interface(struct device *dev)
 		goto err;
 
 	intf->condition = USB_INTERFACE_BOUND;
+
+	/* If the LPM disable succeeded, balance the ref counts. */
+	if (!lpm_disable_error)
+		usb_unlocked_enable_lpm(udev);
+
 	usb_autosuspend_device(udev);
 	return error;
 
@@ -361,7 +386,7 @@ static int usb_unbind_interface(struct device *dev)
 	struct usb_driver *driver = to_usb_driver(dev->driver);
 	struct usb_interface *intf = to_usb_interface(dev);
 	struct usb_device *udev;
-	int error, r;
+	int error, r, lpm_disable_error;
 
 	intf->condition = USB_INTERFACE_UNBINDING;
 
@@ -369,6 +394,13 @@ static int usb_unbind_interface(struct device *dev)
 	udev = interface_to_usbdev(intf);
 	error = usb_autoresume_device(udev);
 
+	/* Hub-initiated LPM policy may change, so attempt to disable LPM until
+	 * the driver is unbound.  If LPM isn't disabled, that's fine because it
+	 * wouldn't be enabled unless all the bound interfaces supported
+	 * hub-initiated LPM.
+	 */
+	lpm_disable_error = usb_unlocked_disable_lpm(udev);
+
 	/* Terminate all URBs for this interface unless the driver
 	 * supports "soft" unbinding.
 	 */
@@ -402,6 +434,10 @@ static int usb_unbind_interface(struct device *dev)
 	intf->condition = USB_INTERFACE_UNBOUND;
 	intf->needs_remote_wakeup = 0;
 
+	/* Attempt to re-enable USB3 LPM, if the disable succeeded. */
+	if (!lpm_disable_error)
+		usb_unlocked_enable_lpm(udev);
+
 	/* Unbound interfaces are always runtime-PM-disabled and -suspended */
 	if (driver->supports_autosuspend)
 		pm_runtime_disable(dev);
@@ -442,17 +478,29 @@ int usb_driver_claim_interface(struct usb_driver *driver,
 				struct usb_interface *iface, void *priv)
 {
 	struct device *dev = &iface->dev;
+	struct usb_device *udev;
 	int retval = 0;
+	int lpm_disable_error;
 
 	if (dev->driver)
 		return -EBUSY;
 
+	udev = interface_to_usbdev(iface);
+
 	dev->driver = &driver->drvwrap.driver;
 	usb_set_intfdata(iface, priv);
 	iface->needs_binding = 0;
 
 	iface->condition = USB_INTERFACE_BOUND;
 
+	/* Disable LPM until this driver is bound. */
+	lpm_disable_error = usb_unlocked_disable_lpm(udev);
+	if (lpm_disable_error && driver->disable_hub_initiated_lpm) {
+		dev_err(&iface->dev, "%s Failed to disable LPM for driver %s\n.",
+				__func__, driver->name);
+		return -ENOMEM;
+	}
+
 	/* Claimed interfaces are initially inactive (suspended) and
 	 * runtime-PM-enabled, but only if the driver has autosuspend
 	 * support.  Otherwise they are marked active, to prevent the
@@ -471,6 +519,10 @@ int usb_driver_claim_interface(struct usb_driver *driver,
 	if (device_is_registered(dev))
 		retval = device_bind_driver(dev);
 
+	/* Attempt to re-enable USB3 LPM, if the disable was successful. */
+	if (!lpm_disable_error)
+		usb_unlocked_enable_lpm(udev);
+
 	return retval;
 }
 EXPORT_SYMBOL_GPL(usb_driver_claim_interface);