USB: Add support to enable/disable USB3 link states.

There are various functions within the USB core that will need to
disable USB 3.0 link power states.  For example, when a USB device
driver is being bound to an interface, we need to disable USB 3.0 LPM
until we know if the driver will allow hub-initiated LPM transitions.
Another example is when the USB core is switching alternate interface
settings.  The USB 3.0 timeout values are dependent on what endpoints
are enabled, so we want to ensure that LPM is disabled until the new alt
setting is fully installed.

Multiple functions need to disable LPM, and those functions can even be
nested.  For example, usb_bind_interface() could disable LPM, and then
call into the driver probe function, which may attempt to switch to a
different alt setting.  Therefore, we need to keep a count of the number
of functions that require LPM to be disabled at any point in time.

Introduce two new USB core API calls, usb_disable_lpm() and
usb_enable_lpm().  These functions increment and decrement a new
variable in the usb_device, lpm_disable_count.  If usb_disable_lpm()
fails, it will call usb_enable_lpm() in order to balance the
lpm_disable_count.

These two new functions must be called with the bandwidth_mutex locked.
If the bandwidth_mutex is not already held by the caller, it should
instead call usb_unlocked_disable_lpm() and usb_enable_lpm(), which take
the bandwidth_mutex before calling usb_disable_lpm() and
usb_enable_lpm(), respectively.

Introduce a new variable (timeout) in the usb3_lpm_params structure to
keep track of the currently enabled U1/U2 timeout values.  When
usb_disable_lpm() is called, and the USB device has the U1 or U2
timeouts set to a non-zero value (meaning either device-initiated or
hub-initiated LPM is enabled), attempt to disable LPM, regardless of the
state of the lpm_disable_count.  We want to ensure that all callers can
be guaranteed that LPM is disabled if usb_disable_lpm() returns zero.

Otherwise the following scenario could occur:

1. Driver A is being bound to interface 1.  usb_probe_interface()
disables LPM.  Driver A doesn't care if hub-initiated LPM is enabled, so
even though usb_disable_lpm() fails, the probe of the driver continues,
and the bandwidth mutex is dropped.

2. Meanwhile, Driver B is being bound to interface 2.
usb_probe_interface() grabs the bandwidth mutex and calls
usb_disable_lpm().  That call should attempt to disable LPM, even
though the lpm_disable_count is set to 1 by Driver A.

For usb_enable_lpm(), we attempt to enable LPM only when the
lpm_disable_count is zero.  If some step in enabling LPM fails, it will
only have a minimal impact on power consumption, and all USB device
drivers should still work properly.  Therefore don't bother to return
any error codes.

Don't enable device-initiated LPM if the device is unconfigured.  The
USB device will only accept the U1/U2_ENABLE control transfers in the
configured state.  Do enable hub-initiated LPM in that case, since
devices are allowed to accept the LGO_Ux link commands in any state.

Don't enable or disable LPM if the device is marked as not being LPM
capable.  This can happen if:
 - the USB device doesn't have a SS BOS descriptor,
 - the device's parent hub has a zeroed bHeaderDecodeLatency value, or
 - the xHCI host doesn't support LPM.

Signed-off-by: Sarah Sharp <sarah.a.sharp@linux.intel.com>
Cc: Andiry Xu <andiry.xu@amd.com>
Cc: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Sarah Sharp <sarah.a.sharp@linux.intel.com>

5 files changed, 489 insertions, 2 deletions

diff --git a/drivers/usb/core/hub.c b/drivers/usb/core/hub.c
index 5219507bf227..fd1ec481aec1 100644
--- a/drivers/usb/core/hub.c
+++ b/drivers/usb/core/hub.c
@@ -3050,11 +3050,425 @@ void usb_root_hub_lost_power(struct usb_device *rhdev)
 }
 EXPORT_SYMBOL_GPL(usb_root_hub_lost_power);
 
+static const char * const usb3_lpm_names[]  = {
+	"U0",
+	"U1",
+	"U2",
+	"U3",
+};
+
+/*
+ * Send a Set SEL control transfer to the device, prior to enabling
+ * device-initiated U1 or U2.  This lets the device know the exit latencies from
+ * the time the device initiates a U1 or U2 exit, to the time it will receive a
+ * packet from the host.
+ *
+ * This function will fail if the SEL or PEL values for udev are greater than
+ * the maximum allowed values for the link state to be enabled.
+ */
+static int usb_req_set_sel(struct usb_device *udev, enum usb3_link_state state)
+{
+	struct usb_set_sel_req *sel_values;
+	unsigned long long u1_sel;
+	unsigned long long u1_pel;
+	unsigned long long u2_sel;
+	unsigned long long u2_pel;
+	int ret;
+
+	/* Convert SEL and PEL stored in ns to us */
+	u1_sel = DIV_ROUND_UP(udev->u1_params.sel, 1000);
+	u1_pel = DIV_ROUND_UP(udev->u1_params.pel, 1000);
+	u2_sel = DIV_ROUND_UP(udev->u2_params.sel, 1000);
+	u2_pel = DIV_ROUND_UP(udev->u2_params.pel, 1000);
+
+	/*
+	 * Make sure that the calculated SEL and PEL values for the link
+	 * state we're enabling aren't bigger than the max SEL/PEL
+	 * value that will fit in the SET SEL control transfer.
+	 * Otherwise the device would get an incorrect idea of the exit
+	 * latency for the link state, and could start a device-initiated
+	 * U1/U2 when the exit latencies are too high.
+	 */
+	if ((state == USB3_LPM_U1 &&
+				(u1_sel > USB3_LPM_MAX_U1_SEL_PEL ||
+				 u1_pel > USB3_LPM_MAX_U1_SEL_PEL)) ||
+			(state == USB3_LPM_U2 &&
+			 (u2_sel > USB3_LPM_MAX_U2_SEL_PEL ||
+			  u2_pel > USB3_LPM_MAX_U2_SEL_PEL))) {
+		dev_dbg(&udev->dev, "Device-initiated %s disabled due "
+				"to long SEL %llu ms or PEL %llu ms\n",
+				usb3_lpm_names[state], u1_sel, u1_pel);
+		return -EINVAL;
+	}
+
+	/*
+	 * If we're enabling device-initiated LPM for one link state,
+	 * but the other link state has a too high SEL or PEL value,
+	 * just set those values to the max in the Set SEL request.
+	 */
+	if (u1_sel > USB3_LPM_MAX_U1_SEL_PEL)
+		u1_sel = USB3_LPM_MAX_U1_SEL_PEL;
+
+	if (u1_pel > USB3_LPM_MAX_U1_SEL_PEL)
+		u1_pel = USB3_LPM_MAX_U1_SEL_PEL;
+
+	if (u2_sel > USB3_LPM_MAX_U2_SEL_PEL)
+		u2_sel = USB3_LPM_MAX_U2_SEL_PEL;
+
+	if (u2_pel > USB3_LPM_MAX_U2_SEL_PEL)
+		u2_pel = USB3_LPM_MAX_U2_SEL_PEL;
+
+	/*
+	 * usb_enable_lpm() can be called as part of a failed device reset,
+	 * which may be initiated by an error path of a mass storage driver.
+	 * Therefore, use GFP_NOIO.
+	 */
+	sel_values = kmalloc(sizeof *(sel_values), GFP_NOIO);
+	if (!sel_values)
+		return -ENOMEM;
+
+	sel_values->u1_sel = u1_sel;
+	sel_values->u1_pel = u1_pel;
+	sel_values->u2_sel = cpu_to_le16(u2_sel);
+	sel_values->u2_pel = cpu_to_le16(u2_pel);
+
+	ret = usb_control_msg(udev, usb_sndctrlpipe(udev, 0),
+			USB_REQ_SET_SEL,
+			USB_RECIP_DEVICE,
+			0, 0,
+			sel_values, sizeof *(sel_values),
+			USB_CTRL_SET_TIMEOUT);
+	kfree(sel_values);
+	return ret;
+}
+
+/*
+ * Enable or disable device-initiated U1 or U2 transitions.
+ */
+static int usb_set_device_initiated_lpm(struct usb_device *udev,
+		enum usb3_link_state state, bool enable)
+{
+	int ret;
+	int feature;
+
+	switch (state) {
+	case USB3_LPM_U1:
+		feature = USB_DEVICE_U1_ENABLE;
+		break;
+	case USB3_LPM_U2:
+		feature = USB_DEVICE_U2_ENABLE;
+		break;
+	default:
+		dev_warn(&udev->dev, "%s: Can't %s non-U1 or U2 state.\n",
+				__func__, enable ? "enable" : "disable");
+		return -EINVAL;
+	}
+
+	if (udev->state != USB_STATE_CONFIGURED) {
+		dev_dbg(&udev->dev, "%s: Can't %s %s state "
+				"for unconfigured device.\n",
+				__func__, enable ? "enable" : "disable",
+				usb3_lpm_names[state]);
+		return 0;
+	}
+
+	if (enable) {
+		/*
+		 * First, let the device know about the exit latencies
+		 * associated with the link state we're about to enable.
+		 */
+		ret = usb_req_set_sel(udev, state);
+		if (ret < 0) {
+			dev_warn(&udev->dev, "Set SEL for device-initiated "
+					"%s failed.\n", usb3_lpm_names[state]);
+			return -EBUSY;
+		}
+		/*
+		 * Now send the control transfer to enable device-initiated LPM
+		 * for either U1 or U2.
+		 */
+		ret = usb_control_msg(udev, usb_sndctrlpipe(udev, 0),
+				USB_REQ_SET_FEATURE,
+				USB_RECIP_DEVICE,
+				feature,
+				0, NULL, 0,
+				USB_CTRL_SET_TIMEOUT);
+	} else {
+		ret = usb_control_msg(udev, usb_sndctrlpipe(udev, 0),
+				USB_REQ_CLEAR_FEATURE,
+				USB_RECIP_DEVICE,
+				feature,
+				0, NULL, 0,
+				USB_CTRL_SET_TIMEOUT);
+	}
+	if (ret < 0) {
+		dev_warn(&udev->dev, "%s of device-initiated %s failed.\n",
+				enable ? "Enable" : "Disable",
+				usb3_lpm_names[state]);
+		return -EBUSY;
+	}
+	return 0;
+}
+
+static int usb_set_lpm_timeout(struct usb_device *udev,
+		enum usb3_link_state state, int timeout)
+{
+	int ret;
+	int feature;
+
+	switch (state) {
+	case USB3_LPM_U1:
+		feature = USB_PORT_FEAT_U1_TIMEOUT;
+		break;
+	case USB3_LPM_U2:
+		feature = USB_PORT_FEAT_U2_TIMEOUT;
+		break;
+	default:
+		dev_warn(&udev->dev, "%s: Can't set timeout for non-U1 or U2 state.\n",
+				__func__);
+		return -EINVAL;
+	}
+
+	if (state == USB3_LPM_U1 && timeout > USB3_LPM_U1_MAX_TIMEOUT &&
+			timeout != USB3_LPM_DEVICE_INITIATED) {
+		dev_warn(&udev->dev, "Failed to set %s timeout to 0x%x, "
+				"which is a reserved value.\n",
+				usb3_lpm_names[state], timeout);
+		return -EINVAL;
+	}
+
+	ret = set_port_feature(udev->parent,
+			USB_PORT_LPM_TIMEOUT(timeout) | udev->portnum,
+			feature);
+	if (ret < 0) {
+		dev_warn(&udev->dev, "Failed to set %s timeout to 0x%x,"
+				"error code %i\n", usb3_lpm_names[state],
+				timeout, ret);
+		return -EBUSY;
+	}
+	if (state == USB3_LPM_U1)
+		udev->u1_params.timeout = timeout;
+	else
+		udev->u2_params.timeout = timeout;
+	return 0;
+}
+
+/*
+ * Enable the hub-initiated U1/U2 idle timeouts, and enable device-initiated
+ * U1/U2 entry.
+ *
+ * We will attempt to enable U1 or U2, but there are no guarantees that the
+ * control transfers to set the hub timeout or enable device-initiated U1/U2
+ * will be successful.
+ *
+ * If we cannot set the parent hub U1/U2 timeout, we attempt to let the xHCI
+ * driver know about it.  If that call fails, it should be harmless, and just
+ * take up more slightly more bus bandwidth for unnecessary U1/U2 exit latency.
+ */
+static void usb_enable_link_state(struct usb_hcd *hcd, struct usb_device *udev,
+		enum usb3_link_state state)
+{
+	int timeout;
+
+	/* We allow the host controller to set the U1/U2 timeout internally
+	 * first, so that it can change its schedule to account for the
+	 * additional latency to send data to a device in a lower power
+	 * link state.
+	 */
+	timeout = hcd->driver->enable_usb3_lpm_timeout(hcd, udev, state);
+
+	/* xHCI host controller doesn't want to enable this LPM state. */
+	if (timeout == 0)
+		return;
+
+	if (timeout < 0) {
+		dev_warn(&udev->dev, "Could not enable %s link state, "
+				"xHCI error %i.\n", usb3_lpm_names[state],
+				timeout);
+		return;
+	}
+
+	if (usb_set_lpm_timeout(udev, state, timeout))
+		/* If we can't set the parent hub U1/U2 timeout,
+		 * device-initiated LPM won't be allowed either, so let the xHCI
+		 * host know that this link state won't be enabled.
+		 */
+		hcd->driver->disable_usb3_lpm_timeout(hcd, udev, state);
+
+	/* Only a configured device will accept the Set Feature U1/U2_ENABLE */
+	else if (udev->actconfig)
+		usb_set_device_initiated_lpm(udev, state, true);
+
+}
+
+/*
+ * Disable the hub-initiated U1/U2 idle timeouts, and disable device-initiated
+ * U1/U2 entry.
+ *
+ * If this function returns -EBUSY, the parent hub will still allow U1/U2 entry.
+ * If zero is returned, the parent will not allow the link to go into U1/U2.
+ *
+ * If zero is returned, device-initiated U1/U2 entry may still be enabled, but
+ * it won't have an effect on the bus link state because the parent hub will
+ * still disallow device-initiated U1/U2 entry.
+ *
+ * If zero is returned, the xHCI host controller may still think U1/U2 entry is
+ * possible.  The result will be slightly more bus bandwidth will be taken up
+ * (to account for U1/U2 exit latency), but it should be harmless.
+ */
+static int usb_disable_link_state(struct usb_hcd *hcd, struct usb_device *udev,
+		enum usb3_link_state state)
+{
+	int feature;
+
+	switch (state) {
+	case USB3_LPM_U1:
+		feature = USB_PORT_FEAT_U1_TIMEOUT;
+		break;
+	case USB3_LPM_U2:
+		feature = USB_PORT_FEAT_U2_TIMEOUT;
+		break;
+	default:
+		dev_warn(&udev->dev, "%s: Can't disable non-U1 or U2 state.\n",
+				__func__);
+		return -EINVAL;
+	}
+
+	if (usb_set_lpm_timeout(udev, state, 0))
+		return -EBUSY;
+
+	usb_set_device_initiated_lpm(udev, state, false);
+
+	if (hcd->driver->disable_usb3_lpm_timeout(hcd, udev, state))
+		dev_warn(&udev->dev, "Could not disable xHCI %s timeout, "
+				"bus schedule bandwidth may be impacted.\n",
+				usb3_lpm_names[state]);
+	return 0;
+}
+
+/*
+ * Disable hub-initiated and device-initiated U1 and U2 entry.
+ * Caller must own the bandwidth_mutex.
+ *
+ * This will call usb_enable_lpm() on failure, which will decrement
+ * lpm_disable_count, and will re-enable LPM if lpm_disable_count reaches zero.
+ */
+int usb_disable_lpm(struct usb_device *udev)
+{
+	struct usb_hcd *hcd;
+
+	if (!udev || !udev->parent ||
+			udev->speed != USB_SPEED_SUPER ||
+			!udev->lpm_capable)
+		return 0;
+
+	hcd = bus_to_hcd(udev->bus);
+	if (!hcd || !hcd->driver->disable_usb3_lpm_timeout)
+		return 0;
+
+	udev->lpm_disable_count++;
+	if ((udev->u1_params.timeout == 0 && udev->u1_params.timeout == 0))
+		return 0;
+
+	/* If LPM is enabled, attempt to disable it. */
+	if (usb_disable_link_state(hcd, udev, USB3_LPM_U1))
+		goto enable_lpm;
+	if (usb_disable_link_state(hcd, udev, USB3_LPM_U2))
+		goto enable_lpm;
+
+	return 0;
+
+enable_lpm:
+	usb_enable_lpm(udev);
+	return -EBUSY;
+}
+EXPORT_SYMBOL_GPL(usb_disable_lpm);
+
+/* Grab the bandwidth_mutex before calling usb_disable_lpm() */
+int usb_unlocked_disable_lpm(struct usb_device *udev)
+{
+	struct usb_hcd *hcd = bus_to_hcd(udev->bus);
+	int ret;
+
+	if (!hcd)
+		return -EINVAL;
+
+	mutex_lock(hcd->bandwidth_mutex);
+	ret = usb_disable_lpm(udev);
+	mutex_unlock(hcd->bandwidth_mutex);
+
+	return ret;
+}
+EXPORT_SYMBOL_GPL(usb_unlocked_disable_lpm);
+
+/*
+ * Attempt to enable device-initiated and hub-initiated U1 and U2 entry.  The
+ * xHCI host policy may prevent U1 or U2 from being enabled.
+ *
+ * Other callers may have disabled link PM, so U1 and U2 entry will be disabled
+ * until the lpm_disable_count drops to zero.  Caller must own the
+ * bandwidth_mutex.
+ */
+void usb_enable_lpm(struct usb_device *udev)
+{
+	struct usb_hcd *hcd;
+
+	if (!udev || !udev->parent ||
+			udev->speed != USB_SPEED_SUPER ||
+			!udev->lpm_capable)
+		return;
+
+	udev->lpm_disable_count--;
+	hcd = bus_to_hcd(udev->bus);
+	/* Double check that we can both enable and disable LPM.
+	 * Device must be configured to accept set feature U1/U2 timeout.
+	 */
+	if (!hcd || !hcd->driver->enable_usb3_lpm_timeout ||
+			!hcd->driver->disable_usb3_lpm_timeout)
+		return;
+
+	if (udev->lpm_disable_count > 0)
+		return;
+
+	usb_enable_link_state(hcd, udev, USB3_LPM_U1);
+	usb_enable_link_state(hcd, udev, USB3_LPM_U2);
+}
+EXPORT_SYMBOL_GPL(usb_enable_lpm);
+
+/* Grab the bandwidth_mutex before calling usb_enable_lpm() */
+void usb_unlocked_enable_lpm(struct usb_device *udev)
+{
+	struct usb_hcd *hcd = bus_to_hcd(udev->bus);
+
+	if (!hcd)
+		return;
+
+	mutex_lock(hcd->bandwidth_mutex);
+	usb_enable_lpm(udev);
+	mutex_unlock(hcd->bandwidth_mutex);
+}
+EXPORT_SYMBOL_GPL(usb_unlocked_enable_lpm);
+
+
 #else	/* CONFIG_PM */
 
 #define hub_suspend		NULL
 #define hub_resume		NULL
 #define hub_reset_resume	NULL
+
+int usb_disable_lpm(struct usb_device *udev)
+{
+	return 0;
+}
+
+void usb_enable_lpm(struct usb_device *udev) { }
+
+int usb_unlocked_disable_lpm(struct usb_device *udev)
+{
+	return 0;
+}
+
+void usb_unlocked_enable_lpm(struct usb_device *udev) { }
 #endif
 
 
diff --git a/include/linux/usb.h b/include/linux/usb.h
index 22e7b53123ef..40439dfd81a7 100644
--- a/include/linux/usb.h
+++ b/include/linux/usb.h
@@ -409,6 +409,12 @@ struct usb3_lpm_parameters {
 	 * it will get data.
 	 */
 	unsigned int sel;
+	/*
+	 * The idle timeout value that is currently programmed into the parent
+	 * hub for this device.  When the timer counts to zero, the parent hub
+	 * will initiate an LPM transition to either U1 or U2.
+	 */
+	int timeout;
 };
 
 /**
@@ -468,8 +474,12 @@ struct usb3_lpm_parameters {
  *	specific data for the device.
  * @slot_id: Slot ID assigned by xHCI
  * @removable: Device can be physically removed from this port
- * @u1_params: exit latencies for U1 (USB 3.0 LPM).
- * @u2_params: exit latencies for U2 (USB 3.0 LPM).
+ * @u1_params: exit latencies for USB3 U1 LPM state, and hub-initiated timeout.
+ * @u2_params: exit latencies for USB3 U2 LPM state, and hub-initiated timeout.
+ * @lpm_disable_count: Ref count used by usb_disable_lpm() and usb_enable_lpm()
+ *	to keep track of the number of functions that require USB 3.0 Link Power
+ *	Management to be disabled for this usb_device.  This count should only
+ *	be manipulated by those functions, with the bandwidth_mutex is held.
  *
  * Notes:
  * Usbcore drivers should not set usbdev->state directly.  Instead use
@@ -544,6 +554,7 @@ struct usb_device {
 	enum usb_device_removable removable;
 	struct usb3_lpm_parameters u1_params;
 	struct usb3_lpm_parameters u2_params;
+	unsigned lpm_disable_count;
 };
 #define	to_usb_device(d) container_of(d, struct usb_device, dev)
 
@@ -579,6 +590,12 @@ extern void usb_autopm_put_interface_async(struct usb_interface *intf);
 extern void usb_autopm_get_interface_no_resume(struct usb_interface *intf);
 extern void usb_autopm_put_interface_no_suspend(struct usb_interface *intf);
 
+extern int usb_disable_lpm(struct usb_device *udev);
+extern void usb_enable_lpm(struct usb_device *udev);
+/* Same as above, but these functions lock/unlock the bandwidth_mutex. */
+extern int usb_unlocked_disable_lpm(struct usb_device *udev);
+extern void usb_unlocked_enable_lpm(struct usb_device *udev);
+
 static inline void usb_mark_last_busy(struct usb_device *udev)
 {
 	pm_runtime_mark_last_busy(&udev->dev);
diff --git a/include/linux/usb/ch11.h b/include/linux/usb/ch11.h
index f1d26b6067f1..b6c2863b2c94 100644
--- a/include/linux/usb/ch11.h
+++ b/include/linux/usb/ch11.h
@@ -76,6 +76,8 @@
 #define USB_PORT_FEAT_C_BH_PORT_RESET		29
 #define USB_PORT_FEAT_FORCE_LINKPM_ACCEPT	30
 
+#define USB_PORT_LPM_TIMEOUT(p)			(((p) & 0xff) << 8)
+
 /* USB 3.0 hub remote wake mask bits, see table 10-14 */
 #define USB_PORT_FEAT_REMOTE_WAKE_CONNECT	(1 << 8)
 #define USB_PORT_FEAT_REMOTE_WAKE_DISCONNECT	(1 << 9)
diff --git a/include/linux/usb/ch9.h b/include/linux/usb/ch9.h
index e785d85b617f..43bce9da7a4d 100644
--- a/include/linux/usb/ch9.h
+++ b/include/linux/usb/ch9.h
@@ -935,6 +935,51 @@ enum usb_device_state {
 	 */
 };
 
+enum usb3_link_state {
+	USB3_LPM_U0 = 0,
+	USB3_LPM_U1,
+	USB3_LPM_U2,
+	USB3_LPM_U3
+};
+
+/*
+ * A U1 timeout of 0x0 means the parent hub will reject any transitions to U1.
+ * 0xff means the parent hub will accept transitions to U1, but will not
+ * initiate a transition.
+ *
+ * A U1 timeout of 0x1 to 0x7F also causes the hub to initiate a transition to
+ * U1 after that many microseconds.  Timeouts of 0x80 to 0xFE are reserved
+ * values.
+ *
+ * A U2 timeout of 0x0 means the parent hub will reject any transitions to U2.
+ * 0xff means the parent hub will accept transitions to U2, but will not
+ * initiate a transition.
+ *
+ * A U2 timeout of 0x1 to 0xFE also causes the hub to initiate a transition to
+ * U2 after N*256 microseconds.  Therefore a U2 timeout value of 0x1 means a U2
+ * idle timer of 256 microseconds, 0x2 means 512 microseconds, 0xFE means
+ * 65.024ms.
+ */
+#define USB3_LPM_DISABLED		0x0
+#define USB3_LPM_U1_MAX_TIMEOUT		0x7F
+#define USB3_LPM_U2_MAX_TIMEOUT		0xFE
+#define USB3_LPM_DEVICE_INITIATED	0xFF
+
+struct usb_set_sel_req {
+	__u8	u1_sel;
+	__u8	u1_pel;
+	__le16	u2_sel;
+	__le16	u2_pel;
+} __attribute__ ((packed));
+
+/*
+ * The Set System Exit Latency control transfer provides one byte each for
+ * U1 SEL and U1 PEL, so the max exit latency is 0xFF.  U2 SEL and U2 PEL each
+ * are two bytes long.
+ */
+#define USB3_LPM_MAX_U1_SEL_PEL		0xFF
+#define USB3_LPM_MAX_U2_SEL_PEL		0xFFFF
+
 /*-------------------------------------------------------------------------*/
 
 /*
diff --git a/include/linux/usb/hcd.h b/include/linux/usb/hcd.h
index bbb946437070..7f855d50cdf5 100644
--- a/include/linux/usb/hcd.h
+++ b/include/linux/usb/hcd.h
@@ -344,6 +344,15 @@ struct hc_driver {
 		 */
 	int	(*update_device)(struct usb_hcd *, struct usb_device *);
 	int	(*set_usb2_hw_lpm)(struct usb_hcd *, struct usb_device *, int);
+	/* USB 3.0 Link Power Management */
+		/* Returns the USB3 hub-encoded value for the U1/U2 timeout. */
+	int	(*enable_usb3_lpm_timeout)(struct usb_hcd *,
+			struct usb_device *, enum usb3_link_state state);
+		/* The xHCI host controller can still fail the command to
+		 * disable the LPM timeouts, so this can return an error code.
+		 */
+	int	(*disable_usb3_lpm_timeout)(struct usb_hcd *,
+			struct usb_device *, enum usb3_link_state state);
 };
 
 extern int usb_hcd_link_urb_to_ep(struct usb_hcd *hcd, struct urb *urb);