usb: core: lpm: add sysfs node for usb3 lpm permit

USB3 LPM is default on in Linux kernel if both xHCI host controller
and the USB devices declare to be LPM-capable. Unfortunately, some
devices are known to work well with LPM disabled, but to be broken
if LPM is enabled, although it declares the LPM capability.  Users
won't be able to use this kind of devices, until someone puts them
in the kernel blacklist and gets the kernel upgraded.

This patch adds a sysfs node to permit or forbit USB3 LPM U1 or U2
entry for a port. The settings apply to both before and after device
enumeration. Supported values are "0" - neither u1 nor u2 permitted,
"u1" - only u1 is permitted, "u2" - only u2 is permitted, "u1_u2" -
both u1 and u2 are permitted. With this interface, users can use an
LPM-unfriendly USB device on a released Linux kernel.

Signed-off-by: Lu Baolu <baolu.lu@linux.intel.com>
Signed-off-by: Zhuang Jin Can <jin.can.zhuang@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 88 insertions, 1 deletions

diff --git a/drivers/usb/core/port.c b/drivers/usb/core/port.c
index 210618319f10..cb18ce0d9177 100644
--- a/drivers/usb/core/port.c
+++ b/drivers/usb/core/port.c
@@ -50,6 +50,72 @@ static ssize_t connect_type_show(struct device *dev,
 }
 static DEVICE_ATTR_RO(connect_type);
 
+static ssize_t usb3_lpm_permit_show(struct device *dev,
+			      struct device_attribute *attr, char *buf)
+{
+	struct usb_port *port_dev = to_usb_port(dev);
+	const char *p;
+
+	if (port_dev->usb3_lpm_u1_permit) {
+		if (port_dev->usb3_lpm_u2_permit)
+			p = "u1_u2";
+		else
+			p = "u1";
+	} else {
+		if (port_dev->usb3_lpm_u2_permit)
+			p = "u2";
+		else
+			p = "0";
+	}
+
+	return sprintf(buf, "%s\n", p);
+}
+
+static ssize_t usb3_lpm_permit_store(struct device *dev,
+			       struct device_attribute *attr,
+			       const char *buf, size_t count)
+{
+	struct usb_port *port_dev = to_usb_port(dev);
+	struct usb_device *udev = port_dev->child;
+	struct usb_hcd *hcd;
+
+	if (!strncmp(buf, "u1_u2", 5)) {
+		port_dev->usb3_lpm_u1_permit = 1;
+		port_dev->usb3_lpm_u2_permit = 1;
+
+	} else if (!strncmp(buf, "u1", 2)) {
+		port_dev->usb3_lpm_u1_permit = 1;
+		port_dev->usb3_lpm_u2_permit = 0;
+
+	} else if (!strncmp(buf, "u2", 2)) {
+		port_dev->usb3_lpm_u1_permit = 0;
+		port_dev->usb3_lpm_u2_permit = 1;
+
+	} else if (!strncmp(buf, "0", 1)) {
+		port_dev->usb3_lpm_u1_permit = 0;
+		port_dev->usb3_lpm_u2_permit = 0;
+	} else
+		return -EINVAL;
+
+	/* If device is connected to the port, disable or enable lpm
+	 * to make new u1 u2 setting take effect immediately.
+	 */
+	if (udev) {
+		hcd = bus_to_hcd(udev->bus);
+		if (!hcd)
+			return -EINVAL;
+		usb_lock_device(udev);
+		mutex_lock(hcd->bandwidth_mutex);
+		if (!usb_disable_lpm(udev))
+			usb_enable_lpm(udev);
+		mutex_unlock(hcd->bandwidth_mutex);
+		usb_unlock_device(udev);
+	}
+
+	return count;
+}
+static DEVICE_ATTR_RW(usb3_lpm_permit);
+
 static struct attribute *port_dev_attrs[] = {
 	&dev_attr_connect_type.attr,
 	NULL,
@@ -64,6 +130,21 @@ static const struct attribute_group *port_dev_group[] = {
 	NULL,
 };
 
+static struct attribute *port_dev_usb3_attrs[] = {
+	&dev_attr_usb3_lpm_permit.attr,
+	NULL,
+};
+
+static struct attribute_group port_dev_usb3_attr_grp = {
+	.attrs = port_dev_usb3_attrs,
+};
+
+static const struct attribute_group *port_dev_usb3_group[] = {
+	&port_dev_attr_grp,
+	&port_dev_usb3_attr_grp,
+	NULL,
+};
+
 static void usb_port_device_release(struct device *dev)
 {
 	struct usb_port *port_dev = to_usb_port(dev);
@@ -401,6 +482,7 @@ static void find_and_link_peer(struct usb_hub *hub, int port1)
 int usb_hub_create_port_device(struct usb_hub *hub, int port1)
 {
 	struct usb_port *port_dev;
+	struct usb_device *hdev = hub->hdev;
 	int retval;
 
 	port_dev = kzalloc(sizeof(*port_dev), GFP_KERNEL);
@@ -417,7 +499,12 @@ int usb_hub_create_port_device(struct usb_hub *hub, int port1)
 	port_dev->portnum = port1;
 	set_bit(port1, hub->power_bits);
 	port_dev->dev.parent = hub->intfdev;
-	port_dev->dev.groups = port_dev_group;
+	if (hub_is_superspeed(hdev)) {
+		port_dev->usb3_lpm_u1_permit = 1;
+		port_dev->usb3_lpm_u2_permit = 1;
+		port_dev->dev.groups = port_dev_usb3_group;
+	} else
+		port_dev->dev.groups = port_dev_group;
 	port_dev->dev.type = &usb_port_device_type;
 	port_dev->dev.driver = &usb_port_driver;
 	if (hub_is_superspeed(hub->hdev))