usbcore: add sysfs support to xHCI usb3 hardware LPM

Add a sysfs node to make it easier to verify if LPM is supported and being
enabled for USB 3.0 devices.
Signed-off-by: Kevin Strasser <kevin.strasser@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Documentation/ABI/testing/sysfs-bus-usb

@@ -114,6 +114,20 @@ Description:
 		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
+Contact:	Kevin Strasser <kevin.strasser@linux.intel.com>
+Description:
+		If CONFIG_PM_RUNTIME 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, 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.
+
 What:		/sys/bus/usb/devices/.../removable
 Date:		February 2012
 Contact:	Matthew Garrett <mjg@redhat.com>

Documentation/usb/power-management.txt

@@ -521,10 +521,10 @@ enabling hardware LPM, the host can automatically put the device into
 lower power state(L1 for usb2.0 devices, or U1/U2 for usb3.0 devices),
 which state device can enter and resume very quickly.
 
-The user interface for controlling USB2 hardware LPM is located in the
+The user interface for controlling hardware LPM is located in the
 power/ subdirectory of each USB device's sysfs directory, that is, in
 /sys/bus/usb/devices/.../power/ where "..." is the device's ID. The
-relevant attribute files is usb2_hardware_lpm.
+relevant attribute files are usb2_hardware_lpm and usb3_hardware_lpm.
 
 	power/usb2_hardware_lpm
 
@@ -537,6 +537,17 @@ relevant attribute files is usb2_hardware_lpm.
 		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
+
+		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.
 
 	USB Port Power Control
 	----------------------

drivers/usb/core/hub.c

@@ -3950,6 +3950,8 @@ int usb_disable_lpm(struct usb_device *udev)
 	if (usb_disable_link_state(hcd, udev, USB3_LPM_U2))
 		goto enable_lpm;
 
+	udev->usb3_lpm_enabled = 0;
+
 	return 0;
 
 enable_lpm:
@@ -4007,6 +4009,8 @@ void usb_enable_lpm(struct usb_device *udev)
 
 	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

@@ -531,6 +531,25 @@ static ssize_t usb2_lpm_besl_store(struct device *dev,
 }
 static DEVICE_ATTR_RW(usb2_lpm_besl);
 
+static ssize_t usb3_hardware_lpm_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_enabled)
+		p = "enabled";
+	else
+		p = "disabled";
+
+	usb_unlock_device(udev);
+
+	return sprintf(buf, "%s\n", p);
+}
+static DEVICE_ATTR_RO(usb3_hardware_lpm);
+
 static struct attribute *usb2_hardware_lpm_attr[] = {
 	&dev_attr_usb2_hardware_lpm.attr,
 	&dev_attr_usb2_lpm_l1_timeout.attr,
@@ -542,6 +561,15 @@ static struct attribute_group usb2_hardware_lpm_attr_group = {
 	.attrs	= usb2_hardware_lpm_attr,
 };
 
+static struct attribute *usb3_hardware_lpm_attr[] = {
+	&dev_attr_usb3_hardware_lpm.attr,
+	NULL,
+};
+static struct attribute_group usb3_hardware_lpm_attr_group = {
+	.name	= power_group_name,
+	.attrs	= usb3_hardware_lpm_attr,
+};
+
 static struct attribute *power_attrs[] = {
 	&dev_attr_autosuspend.attr,
 	&dev_attr_level.attr,
@@ -564,6 +592,9 @@ static int add_power_attributes(struct device *dev)
 		if (udev->usb2_hw_lpm_capable == 1)
 			rc = sysfs_merge_group(&dev->kobj,
 					&usb2_hardware_lpm_attr_group);
+		if (udev->lpm_capable == 1)
+			rc = sysfs_merge_group(&dev->kobj,
+					&usb3_hardware_lpm_attr_group);
 	}
 
 	return rc;