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Subject[PATCH v2] Add driver to force WMI Thunderbolt controller power status
Date
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>
---
changes from v1 to v2:
* Add ABI documentation
* Update thunderbolt.rst
* Remove unnecessary cast
* Remove unneeded whitespace
* Adjust references of "Intel Wmi thunderbolt" ->
"Intel WMI thunderbolt force power"

.../testing/sysfs-platform-intel-wmi-thunderbolt | 11 +++
Documentation/admin-guide/thunderbolt.rst | 15 ++++
MAINTAINERS | 5 ++
drivers/platform/x86/Kconfig | 13 +++
drivers/platform/x86/Makefile | 1 +
drivers/platform/x86/intel-wmi-thunderbolt.c | 96 ++++++++++++++++++++++
6 files changed, 141 insertions(+)
create mode 100644 Documentation/ABI/testing/sysfs-platform-intel-wmi-thunderbolt
create mode 100644 drivers/platform/x86/intel-wmi-thunderbolt.c

diff --git a/Documentation/ABI/testing/sysfs-platform-intel-wmi-thunderbolt b/Documentation/ABI/testing/sysfs-platform-intel-wmi-thunderbolt
new file mode 100644
index 0000000..7b8e61a
--- /dev/null
+++ b/Documentation/ABI/testing/sysfs-platform-intel-wmi-thunderbolt
@@ -0,0 +1,11 @@
+What: /sys/devices/platform/<platform>/force_power
+Date: September 2017
+KernelVersion: 4.14
+Contact: "Mario LimonciellO" <mario.limonciello@dell.com>
+Description:
+ Modify the platform force power state, influencing
+ Thunderbolt controllers to turn on or off when no
+ devices are connected (write-only)
+ There are two available states:
+ * 0 -> Force power disabled
+ * 1 -> Force power enabled
diff --git a/Documentation/admin-guide/thunderbolt.rst b/Documentation/admin-guide/thunderbolt.rst
index 6a4cd1f..dadcd66 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.
diff --git a/MAINTAINERS b/MAINTAINERS
index 1c3feff..9a6b73e 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -3949,6 +3949,11 @@ M: Pali Rohár <pali.rohar@gmail.com>
S: Maintained
F: drivers/platform/x86/dell-wmi.c

+INTEL WMI THUNDERBOLT FORCE POWER DRIVER
+M: Mario Limonciello <mario.limonciello@dell.com>
+S: Maintained
+F: drivers/platform/x86/intel-wmi-thunderbolt.c
+
DELTA ST MEDIA DRIVER
M: Hugues Fruchet <hugues.fruchet@st.com>
L: linux-media@vger.kernel.org
diff --git a/drivers/platform/x86/Kconfig b/drivers/platform/x86/Kconfig
index 80b8795..f401ae4 100644
--- a/drivers/platform/x86/Kconfig
+++ b/drivers/platform/x86/Kconfig
@@ -658,6 +658,19 @@ config WMI_BMOF
To compile this driver as a module, choose M here: the module will
be called wmi-bmof.

+config INTEL_WMI_THUNDERBOLT
+ tristate "Intel WMI thunderbolt force power driver"
+ depends on ACPI_WMI
+ default ACPI_WMI
+ ---help---
+ Say Y here if you want to be able to use the WMI interface on select
+ systems to force the power control of Intel Thunderbolt controllers.
+ This is useful for updating the firmware when devices are not plugged
+ into the controller.
+
+ To compile this driver as a module, choose M here: the module will
+ be called intel-wmi-thunderbolt.
+
config MSI_WMI
tristate "MSI WMI extras"
depends on ACPI_WMI
diff --git a/drivers/platform/x86/Makefile b/drivers/platform/x86/Makefile
index 91cec17..2b315d0 100644
--- a/drivers/platform/x86/Makefile
+++ b/drivers/platform/x86/Makefile
@@ -39,6 +39,7 @@ obj-$(CONFIG_PEAQ_WMI) += peaq-wmi.o
obj-$(CONFIG_SURFACE3_WMI) += surface3-wmi.o
obj-$(CONFIG_TOPSTAR_LAPTOP) += topstar-laptop.o
obj-$(CONFIG_WMI_BMOF) += wmi-bmof.o
+obj-$(CONFIG_INTEL_WMI_THUNDERBOLT) += intel-wmi-thunderbolt.o

# toshiba_acpi must link after wmi to ensure that wmi devices are found
# before toshiba_acpi initializes
diff --git a/drivers/platform/x86/intel-wmi-thunderbolt.c b/drivers/platform/x86/intel-wmi-thunderbolt.c
new file mode 100644
index 0000000..e8c98dc
--- /dev/null
+++ b/drivers/platform/x86/intel-wmi-thunderbolt.c
@@ -0,0 +1,96 @@
+/*
+ * WMI Thunderbolt driver
+ *
+ * Copyright (C) 2017 Dell Inc. All Rights Reserved.
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 as published
+ * by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ */
+
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+
+#include <linux/acpi.h>
+#include <linux/device.h>
+#include <linux/fs.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/string.h>
+#include <linux/sysfs.h>
+#include <linux/types.h>
+#include <linux/wmi.h>
+
+#define INTEL_WMI_THUNDERBOLT_GUID "86CCFD48-205E-4A77-9C48-2021CBEDE341"
+
+static ssize_t force_power_store(struct device *dev,
+ struct device_attribute *attr,
+ const char *buf, size_t count)
+{
+ struct acpi_buffer input;
+ acpi_status status;
+ u8 mode;
+
+ input.length = sizeof(u8);
+ input.pointer = &mode;
+ mode = hex_to_bin(buf[0]);
+ if (mode == 0 || mode == 1) {
+ status = wmi_evaluate_method(INTEL_WMI_THUNDERBOLT_GUID, 0, 1,
+ &input, NULL);
+ if (ACPI_FAILURE(status)) {
+ pr_err("intel-wmi-thunderbolt: failed setting %s\n",
+ buf);
+ return -ENODEV;
+ }
+ } else {
+ pr_err("intel-wmi-thunderbolt: unsupported mode: %d", mode);
+ }
+ return count;
+}
+
+static DEVICE_ATTR_WO(force_power);
+
+static struct attribute *tbt_attrs[] = {
+ &dev_attr_force_power.attr,
+ NULL
+};
+
+static const struct attribute_group tbt_attribute_group = {
+ .attrs = tbt_attrs,
+};
+
+static int intel_wmi_thunderbolt_probe(struct wmi_device *wdev)
+{
+ return sysfs_create_group(&wdev->dev.kobj, &tbt_attribute_group);
+}
+
+static int intel_wmi_thunderbolt_remove(struct wmi_device *wdev)
+{
+ sysfs_remove_group(&wdev->dev.kobj, &tbt_attribute_group);
+ return 0;
+}
+
+static const struct wmi_device_id intel_wmi_thunderbolt_id_table[] = {
+ { .guid_string = INTEL_WMI_THUNDERBOLT_GUID },
+ { },
+};
+
+static struct wmi_driver intel_wmi_thunderbolt_driver = {
+ .driver = {
+ .name = "intel-wmi-thunderbolt",
+ },
+ .probe = intel_wmi_thunderbolt_probe,
+ .remove = intel_wmi_thunderbolt_remove,
+ .id_table = intel_wmi_thunderbolt_id_table,
+};
+
+module_wmi_driver(intel_wmi_thunderbolt_driver);
+
+MODULE_ALIAS("wmi:" INTEL_WMI_THUNDERBOLT_GUID);
+MODULE_AUTHOR("Mario Limonciello <mario.limonciello@dell.com>");
+MODULE_DESCRIPTION("Intel WMI Thunderbolt force power driver");
+MODULE_LICENSE("GPL");
--
2.7.4
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