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authorMario Limonciello <mario.limonciello@dell.com>2017-09-08 18:23:11 +0300
committerAndy Shevchenko <andriy.shevchenko@linux.intel.com>2017-09-20 16:07:22 +0300
commitce6a90027c10f970f872de5db0294f9e3e969f1c (patch)
tree8f370602c3ae125a6bc68dc3489f395982937069 /Documentation/admin-guide
parent2bd6bf03f4c1c59381d62c61d03f6cc3fe71f66e (diff)
downloadlinux-ce6a90027c10f970f872de5db0294f9e3e969f1c.tar.xz
platform/x86: Add driver to force WMI Thunderbolt controller power status
Current implementations of Intel Thunderbolt controllers will go into a low power mode when not in use. Many machines containing these controllers also have a GPIO wired up that can force the controller awake. This is offered via a ACPI-WMI interface intended to be manipulated by a userspace utility. This mechanism is provided by Intel to OEMs to include in BIOS. It uses an industry wide GUID that is populated in a separate _WDG entry with no binary MOF. This interface allows software such as fwupd to wake up thunderbolt controllers to query the firmware version or flash new firmware. Signed-off-by: Mario Limonciello <mario.limonciello@dell.com> Reviewed-by: Mika Westerberg <mika.westerberg@linux.intel.com> Reviewed-by: Yehezkel Bernat <yehezkel.bernat@intel.com> Signed-off-by: Darren Hart (VMware) <dvhart@infradead.org> [andy fixed merge conflicts and bump kernel version for ABI] Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Diffstat (limited to 'Documentation/admin-guide')
-rw-r--r--Documentation/admin-guide/thunderbolt.rst15
1 files changed, 15 insertions, 0 deletions
diff --git a/Documentation/admin-guide/thunderbolt.rst b/Documentation/admin-guide/thunderbolt.rst
index 6a4cd1f159ca..dadcd66ee12f 100644
--- a/Documentation/admin-guide/thunderbolt.rst
+++ b/Documentation/admin-guide/thunderbolt.rst
@@ -197,3 +197,18 @@ information is missing.
To recover from this mode, one needs to flash a valid NVM image to the
host host controller in the same way it is done in the previous chapter.
+
+Forcing power
+-------------
+Many OEMs include a method that can be used to force the power of a
+thunderbolt controller to an "On" state even if nothing is connected.
+If supported by your machine this will be exposed by the WMI bus with
+a sysfs attribute called "force_power".
+
+For example the intel-wmi-thunderbolt driver exposes this attribute in:
+ /sys/devices/platform/PNP0C14:00/wmi_bus/wmi_bus-PNP0C14:00/86CCFD48-205E-4A77-9C48-2021CBEDE341/force_power
+
+ To force the power to on, write 1 to this attribute file.
+ To disable force power, write 0 to this attribute file.
+
+Note: it's currently not possible to query the force power state of a platform.