This patch adds sysfs support to xHCI usb2 hardware LPM, so user can enable
and disable usb2 hardware LPM manually.
Signed-off-by: Andiry Xu <andiry.xu@xxxxxxx>
---
Documentation/usb/power-management.txt | 29 ++++++++++++++++
drivers/usb/core/sysfs.c | 56 ++++++++++++++++++++++++++++++++
2 files changed, 85 insertions(+), 0 deletions(-)
diff --git a/Documentation/usb/power-management.txt b/Documentation/usb/power-management.txt
index c9ffa9c..9e5d9dd 100644
--- a/Documentation/usb/power-management.txt
+++ b/Documentation/usb/power-management.txt
@@ -487,3 +487,32 @@ succeed, it may still remain active and thus cause the system to
resume as soon as the system suspend is complete. Or the remote
wakeup may fail and get lost. Which outcome occurs depends on timing
and on the hardware and firmware design.
+
+
+ xHCI hardware link PM
+ ---------------------
+
+xHCI host controller provides hardware link power management to usb2.0
+(xHCI 1.0 feature) and usb3.0 devices which support link PM. By
+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
+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.
+
+ power/usb2_hardware_lpm
+
+ When a USB2 device which support LPM is plugged to a
+ xHCI host root hub which support software LPM, the
+ host will run a software LPM test for it; if the device
+ enters L1 state and resume successfully and the host
+ supports USB2 hardware LPM, it will enable hardware LPM
+ for the device and the file shows "enable", otherwise
+ it shows "disable". You can write those words to the
+ file to enable/disable USB2 hardware LPM manually only
+ if the device can perform LPM and the host supports
+ hardware LPM. When driver suspend the port into U3
+ state, it will disable hardware LPM first.
diff --git a/drivers/usb/core/sysfs.c b/drivers/usb/core/sysfs.c
index cf05b97..af99bd8 100644
--- a/drivers/usb/core/sysfs.c
+++ b/drivers/usb/core/sysfs.c
@@ -412,9 +412,65 @@ set_level(struct device *dev, struct device_attribute *attr,
static DEVICE_ATTR(level, S_IRUGO | S_IWUSR, show_level, set_level);
+static const char enable_string[] = "enable";
+static const char disable_string[] = "disable";
+
+static ssize_t
+show_usb2_hardware_lpm(struct device *dev, struct device_attribute *attr,
+ char *buf)
+{
+ struct usb_device *udev = to_usb_device(dev);
+ const char *p;
+
+ if (udev->usb2_hw_lpm_enabled == 1)
+ p = enable_string;
+ else
+ p = disable_string;
+
+ return sprintf(buf, "%s\n", p);
+}
+
+static ssize_t
+set_usb2_hardware_lpm(struct device *dev, struct device_attribute *attr,
+ const char *buf, size_t count)
+{
+ struct usb_device *udev = to_usb_device(dev);
+ int len = count;
+ char *cp;
+ int ret;
+
+ cp = memchr(buf, '\n', count);
+ if (cp)
+ len = cp - buf;
+
+ usb_lock_device(udev);
+
+ if (len == sizeof(enable_string) - 1 &&
+ strncmp(buf, enable_string, len) == 0)
+ ret = usb_set_usb2_hardware_lpm(udev, 1);
+
+ else if (len == sizeof(disable_string) - 1 &&
+ strncmp(buf, disable_string, len) == 0)
+ ret = usb_set_usb2_hardware_lpm(udev, 0);
+
+ else
+ ret = -EINVAL;
+
+ usb_unlock_device(udev);
+
+ if (!ret)
+ return count;
+
+ return ret;
+}
+
+static DEVICE_ATTR(usb2_hardware_lpm, S_IRUGO | S_IWUSR, show_usb2_hardware_lpm,
+ set_usb2_hardware_lpm);
+
static struct attribute *power_attrs[] = {
&dev_attr_autosuspend.attr,
&dev_attr_level.attr,
+ &dev_attr_usb2_hardware_lpm.attr,
&dev_attr_connected_duration.attr,
&dev_attr_active_duration.attr,
NULL,
--
1.7.4.1
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