usb: core: lpm: fix usb3_hardware_lpm sysfs node

Commit 655fe4effe0f ("usbcore: add sysfs support to xHCI usb3
hardware LPM") introduced usb3_hardware_lpm sysfs node. This
doesn't show the correct status of USB3 U1 and U2 LPM status.

This patch fixes this by replacing usb3_hardware_lpm with two
nodes, usb3_hardware_lpm_u1 (for U1) and usb3_hardware_lpm_u2
(for U2), and recording the U1/U2 LPM status in right places.

This patch should be back-ported to kernels as old as 4.3,
that contains Commit 655fe4effe0f ("usbcore: add sysfs support
to xHCI usb3 hardware LPM").

Cc: [e-mail]
Signed-off-by: Lu Baolu <[e-mail]>
Signed-off-by: Greg Kroah-Hartman <[e-mail]>

Documentation/ABI/testing/sysfs-bus-usb

···
 		enabled for the device. Developer can write y/Y/1 or n/N/0 to
 		the file to enable/disable the feature.
 
-What:		/sys/bus/usb/devices/.../power/usb3_hardware_lpm
-Date:		June 2015
+What:		/sys/bus/usb/devices/.../power/usb3_hardware_lpm_u1
+		/sys/bus/usb/devices/.../power/usb3_hardware_lpm_u2
+Date:		November 2015
 Contact:	Kevin Strasser <[e-mail]>
+		Lu Baolu <[e-mail]>
 Description:
 		If CONFIG_PM is set and a USB 3.0 lpm-capable device is plugged
 		in to a xHCI host which supports link PM, it will check if U1
 		and U2 exit latencies have been set in the BOS descriptor; if
-		the check is is passed and the host supports USB3 hardware LPM,
+		the check is passed and the host supports USB3 hardware LPM,
 		USB3 hardware LPM will be enabled for the device and the USB
-		device directory will contain a file named
-		power/usb3_hardware_lpm. The file holds a string value (enable
-		or disable) indicating whether or not USB3 hardware LPM is
-		enabled for the device.
+		device directory will contain two files named
+		power/usb3_hardware_lpm_u1 and power/usb3_hardware_lpm_u2. These
+		files hold a string value (enable or disable) indicating whether
+		or not USB3 hardware LPM U1 or U2 is enabled for the device.
 
 What:		/sys/bus/usb/devices/.../removable
 Date:		February 2012

Documentation/usb/power-management.txt

···
 		can write y/Y/1 or n/N/0 to the file to	enable/disable
 		USB2 hardware LPM manually. This is for	test purpose mainly.
 
-	power/usb3_hardware_lpm
+	power/usb3_hardware_lpm_u1
+	power/usb3_hardware_lpm_u2
 
 		When a USB 3.0 lpm-capable device is plugged in to a
 		xHCI host which supports link PM, it will check if U1
 		and U2 exit latencies have been set in the BOS
 		descriptor; if the check is is passed and the host
 		supports USB3 hardware LPM, USB3 hardware LPM will be
-		enabled for the device and this file will be created.
-		The file holds a string value (enable or disable)
-		indicating whether or not USB3 hardware LPM is
-		enabled for the device.
+		enabled for the device and these files will be created.
+		The files hold a string value (enable or disable)
+		indicating whether or not USB3 hardware LPM U1 or U2
+		is enabled for the device.
 
 	USB Port Power Control
 	----------------------

drivers/usb/core/hub.c

···
 		return;
 	}
 
-	if (usb_set_lpm_timeout(udev, state, timeout))
+	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);
+	} else {
+		/* Only a configured device will accept the Set Feature
+		 * U1/U2_ENABLE
+		 */
+		if (udev->actconfig)
+			usb_set_device_initiated_lpm(udev, state, true);
 
-	/* Only a configured device will accept the Set Feature U1/U2_ENABLE */
-	else if (udev->actconfig)
-		usb_set_device_initiated_lpm(udev, state, true);
-
+		/* As soon as usb_set_lpm_timeout(timeout) returns 0, the
+		 * hub-initiated LPM is enabled. Thus, LPM is enabled no
+		 * matter the result of usb_set_device_initiated_lpm().
+		 * The only difference is whether device is able to initiate
+		 * LPM.
+		 */
+		if (state == USB3_LPM_U1)
+			udev->usb3_lpm_u1_enabled = 1;
+		else if (state == USB3_LPM_U2)
+			udev->usb3_lpm_u2_enabled = 1;
+	}
 }
 
 /*
···
 		dev_warn(&udev->dev, "Could not disable xHCI %s timeout, "
 				"bus schedule bandwidth may be impacted.\n",
 				usb3_lpm_names[state]);
+
+	/* As soon as usb_set_lpm_timeout(0) return 0, hub initiated LPM
+	 * is disabled. Hub will disallows link to enter U1/U2 as well,
+	 * even device is initiating LPM. Hence LPM is disabled if hub LPM
+	 * timeout set to 0, no matter device-initiated LPM is disabled or
+	 * not.
+	 */
+	if (state == USB3_LPM_U1)
+		udev->usb3_lpm_u1_enabled = 0;
+	else if (state == USB3_LPM_U2)
+		udev->usb3_lpm_u2_enabled = 0;
+
 	return 0;
 }
 
···
 		goto enable_lpm;
 	if (usb_disable_link_state(hcd, udev, USB3_LPM_U2))
 		goto enable_lpm;
-
-	udev->usb3_lpm_enabled = 0;
 
 	return 0;
 
···
 
 	usb_enable_link_state(hcd, udev, USB3_LPM_U1);
 	usb_enable_link_state(hcd, udev, USB3_LPM_U2);
-
-	udev->usb3_lpm_enabled = 1;
 }
 EXPORT_SYMBOL_GPL(usb_enable_lpm);
 

drivers/usb/core/sysfs.c

···
 }
 static DEVICE_ATTR_RW(usb2_lpm_besl);
 
-static ssize_t usb3_hardware_lpm_show(struct device *dev,
+static ssize_t usb3_hardware_lpm_u1_show(struct device *dev,
 				      struct device_attribute *attr, char *buf)
 {
 	struct usb_device *udev = to_usb_device(dev);
···
 
 	usb_lock_device(udev);
 
-	if (udev->usb3_lpm_enabled)
+	if (udev->usb3_lpm_u1_enabled)
 		p = "enabled";
 	else
 		p = "disabled";
···
 
 	return sprintf(buf, "%s\n", p);
 }
-static DEVICE_ATTR_RO(usb3_hardware_lpm);
+static DEVICE_ATTR_RO(usb3_hardware_lpm_u1);
+
+static ssize_t usb3_hardware_lpm_u2_show(struct device *dev,
+				      struct device_attribute *attr, char *buf)
+{
+	struct usb_device *udev = to_usb_device(dev);
+	const char *p;
+
+	usb_lock_device(udev);
+
+	if (udev->usb3_lpm_u2_enabled)
+		p = "enabled";
+	else
+		p = "disabled";
+
+	usb_unlock_device(udev);
+
+	return sprintf(buf, "%s\n", p);
+}
+static DEVICE_ATTR_RO(usb3_hardware_lpm_u2);
 
 static struct attribute *usb2_hardware_lpm_attr[] = {
 	&dev_attr_usb2_hardware_lpm.attr,
···
 };
 
 static struct attribute *usb3_hardware_lpm_attr[] = {
-	&dev_attr_usb3_hardware_lpm.attr,
+	&dev_attr_usb3_hardware_lpm_u1.attr,
+	&dev_attr_usb3_hardware_lpm_u2.attr,
 	NULL,
 };
 static struct attribute_group usb3_hardware_lpm_attr_group = {
···
 		if (udev->usb2_hw_lpm_capable == 1)
 			rc = sysfs_merge_group(&dev->kobj,
 					&usb2_hardware_lpm_attr_group);
-		if (udev->lpm_capable == 1)
+		if (udev->speed == USB_SPEED_SUPER &&
+				udev->lpm_capable == 1)
 			rc = sysfs_merge_group(&dev->kobj,
 					&usb3_hardware_lpm_attr_group);
 	}

include/linux/usb.h

···
  * @usb2_hw_lpm_enabled: USB2 hardware LPM is enabled
  * @usb2_hw_lpm_allowed: Userspace allows USB 2.0 LPM to be enabled
  * @usb3_lpm_enabled: USB3 hardware LPM enabled
+ * @usb3_lpm_u1_enabled: USB3 hardware U1 LPM enabled
+ * @usb3_lpm_u2_enabled: USB3 hardware U2 LPM enabled
  * @string_langid: language ID for strings
  * @product: iProduct string, if present (static)
  * @manufacturer: iManufacturer string, if present (static)
···
 	unsigned usb2_hw_lpm_enabled:1;
 	unsigned usb2_hw_lpm_allowed:1;
 	unsigned usb3_lpm_enabled:1;
+	unsigned usb3_lpm_u1_enabled:1;
+	unsigned usb3_lpm_u2_enabled:1;
 	int string_langid;
 
 	/* static strings from the device */