There is a new chromebook that contains a different Embedded Controller (codename Wilco) than the rest of the chromebook series. Thus the kernel requires a different driver than the already existing and generalized cros_ec_* drivers. Specifically, this driver adds support for getting and setting the RTC on the EC, adding a binary sysfs attribute that receives ACPI events from the EC, adding a binary sysfs attribute to request telemetry data from the EC (useful for enterprise applications), and adding normal sysfs attributes to get/set various other properties on the EC. The core of the communication with the EC is implemented in wilco_ec/mailbox.c, using a simple byte-level protocol with a checksum, transmitted over an eSPI bus. For debugging purposes, a raw attribute is also provided which can write/read arbitrary bytes to/from the eSPI bus.
We attempted to adhere to the sysfs principles of "one piece of data per attribute" as much as possible, and mostly succeded. However, with the wilco_ec/adv_power.h attributes, which deal with scheduling power usage, we found it most elegant to bundle setting event times for an entire day into a single attribute, so at most you are using attributes formatted as "%d %d %d %d %d %d". With the telemetry attribute, we had to use a binary attribute, instead of the preferable human-readable ascii, in order to keep secure the information which is proprietary to the enterprise service provider. This opaque binary data will be read and sent using a proprietary daemon running on the OS. Finally, the "version" attribute returns a formatted result that looks something like: > cat /sys/bus/platform/devices/GOOG000C\:00/version Label : 95.00.06 SVN Revision : 5960a.06 Model Number : 08;8 Build Date : 11/29/18 The RTC driver is exposed as a standard RTC class driver with read/write functionality. For event notification, the Wilco EC can return extended events that are not handled by standard ACPI objects. These events can include hotkeys which map to standard functions like brightness controls, or information about EC controlled features like the charger or battery. These events are triggered with an ACPI Notify(0x90) and the event data buffer is read through an ACPI method provided by the BIOS which reads the event buffer from EC RAM. These events are then processed, with hotkey events being sent to the input subsystem and other events put into a queue which can be read by a userspace daemon via a sysfs attribute. The rest of the attributes are categorized as either "properties" or "legacy". "legacy" implies that the attribute existed on the EC before it was modified for ChromeOS, and "properties" implies that the attribute exposes functionality that was added to the EC specifically for ChromeOS. They are mostly boolean flags or percentages. A full thread of the development of these patches can be found at https://chromium-review.googlesource.com/c/1371034. This thread contains comments and revisions that could be helpful in understanding how the driver arrived at the state it is in now. The thread also contains some ChromeOS specific patches that actually enable the driver. If you want to test the patch yourself, you would have to install the ChromeOS SDK and cherry pick in these patches. I also wrote some integration tests using the Tast testing framework that ChromeOS uses. It would require a full ChromeOS SDK to actually run the tests, but the source of the tests, written in Go, are useful for understanding what the desired behavior is. You can view the tests here: https://chromium-review.googlesource.com/c/1372575 Thank you for your comments! Changes in v2: - Fixed kernel-doc comments - Fixed include of linux/mfd/cros_ec_lpc_mec.h - cros_ec_lpc_mec_in_range() returns -EINVAL on error - Added parens around macro variables - Removed COMPILE_TEST from Kconfig because inb()/outb() won't work on anything but X86 - Moved everything to wilco_ec/ subdirectory - Moved header file to include/platform_data/ so could be used by future sub-drivers - Tweaked mailbox() - Removed duplicate EC_MAILBOX_DATA_SIZE defs - Removed some error messages / converted to dbg() - Remove license boiler plate - Remove "wilco_ec_sysfs -" docstring prefix - Fix accidental Makefile deletion - Add documentation for sysfs entries - Change "enable ? 0 : 1" to "!enable" - No longer override error code from sysfs_init() - Put attributes in the legacy file to begin with, don't move later - Remove duplicate error messages in sysfs_init() and its caller - Add sysfs documentation - rm duplicate EC_MAILBOX_DATA_SIZE defs - Make docstrings follow kernel style - Fix tags in commit msg - Reading raw now includes ASCII translation - rm license boiler plate - rm "wilco_ec_rtc -" prefix in docstring - Make rtc driver its own module within the drivers/rtc/ directory - Register a rtc device from core.c that is picked up by this driver - rm unused rtc_sync() function - rm "wilco_ec_event -" prefix from docstring - rm license boiler plate - Add sysfs directory documentation - Fix cosmetics - Remove duplicate error messages - rm license boiler plate - rm "wilco_ec_properties -" prefix from docstring - Add documentation - rm license boiler plate - rm "wilco_ec_adv_power - " prefix from docstring - Add documentation - Made format strings in store() and read() functions static - rm "wilco_ec_telemetry - " prefix from docstring - rm license boiler plate - Fix commit msg tag Duncan Laurie (6): platform/chrome: Remove cros_ec dependency in lpc_mec platform/chrome: Add new driver for Wilco EC platform/chrome: Add sysfs attributes platform/chrome: Add support for raw commands in sysfs platform/chrome: rtc: Add RTC driver for Wilco EC platform/chrome: Add event handling Nick Crews (3): platform/chrome: Add EC properties platform/chrome: Add peakshift and adv_batt_charging platform/chrome: Add binary telemetry attributes .../ABI/testing/sysfs-platform-wilcoec | 176 ++++++ drivers/platform/chrome/Kconfig | 4 +- drivers/platform/chrome/Makefile | 2 + drivers/platform/chrome/cros_ec_lpc_mec.c | 52 +- drivers/platform/chrome/cros_ec_lpc_mec.h | 43 +- drivers/platform/chrome/cros_ec_lpc_reg.c | 43 +- drivers/platform/chrome/wilco_ec/Kconfig | 33 ++ drivers/platform/chrome/wilco_ec/Makefile | 6 + drivers/platform/chrome/wilco_ec/adv_power.c | 544 ++++++++++++++++++ drivers/platform/chrome/wilco_ec/adv_power.h | 183 ++++++ drivers/platform/chrome/wilco_ec/core.c | 144 +++++ drivers/platform/chrome/wilco_ec/event.c | 347 +++++++++++ drivers/platform/chrome/wilco_ec/legacy.c | 190 ++++++ drivers/platform/chrome/wilco_ec/legacy.h | 93 +++ drivers/platform/chrome/wilco_ec/mailbox.c | 237 ++++++++ drivers/platform/chrome/wilco_ec/properties.c | 344 +++++++++++ drivers/platform/chrome/wilco_ec/properties.h | 179 ++++++ drivers/platform/chrome/wilco_ec/sysfs.c | 238 ++++++++ drivers/platform/chrome/wilco_ec/telemetry.c | 66 +++ drivers/platform/chrome/wilco_ec/telemetry.h | 41 ++ drivers/platform/chrome/wilco_ec/util.h | 38 ++ drivers/rtc/Kconfig | 11 + drivers/rtc/Makefile | 1 + drivers/rtc/rtc-wilco-ec.c | 178 ++++++ include/linux/platform_data/wilco-ec.h | 186 ++++++ 25 files changed, 3319 insertions(+), 60 deletions(-) create mode 100644 Documentation/ABI/testing/sysfs-platform-wilcoec create mode 100644 drivers/platform/chrome/wilco_ec/Kconfig create mode 100644 drivers/platform/chrome/wilco_ec/Makefile create mode 100644 drivers/platform/chrome/wilco_ec/adv_power.c create mode 100644 drivers/platform/chrome/wilco_ec/adv_power.h create mode 100644 drivers/platform/chrome/wilco_ec/core.c create mode 100644 drivers/platform/chrome/wilco_ec/event.c create mode 100644 drivers/platform/chrome/wilco_ec/legacy.c create mode 100644 drivers/platform/chrome/wilco_ec/legacy.h create mode 100644 drivers/platform/chrome/wilco_ec/mailbox.c create mode 100644 drivers/platform/chrome/wilco_ec/properties.c create mode 100644 drivers/platform/chrome/wilco_ec/properties.h create mode 100644 drivers/platform/chrome/wilco_ec/sysfs.c create mode 100644 drivers/platform/chrome/wilco_ec/telemetry.c create mode 100644 drivers/platform/chrome/wilco_ec/telemetry.h create mode 100644 drivers/platform/chrome/wilco_ec/util.h create mode 100644 drivers/rtc/rtc-wilco-ec.c create mode 100644 include/linux/platform_data/wilco-ec.h -- 2.20.1.97.g81188d93c3-goog
