From ce6a90027c10f970f872de5db0294f9e3e969f1c Mon Sep 17 00:00:00 2001 From: Mario Limonciello Date: Fri, 8 Sep 2017 10:23:11 -0500 Subject: 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 Reviewed-by: Mika Westerberg Reviewed-by: Yehezkel Bernat Signed-off-by: Darren Hart (VMware) [andy fixed merge conflicts and bump kernel version for ABI] Signed-off-by: Andy Shevchenko --- Documentation/admin-guide/thunderbolt.rst | 15 +++++++++++++++ 1 file changed, 15 insertions(+) (limited to 'Documentation/admin-guide/thunderbolt.rst') 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. -- cgit v1.2.3-59-g8ed1b