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), adding a debugfs interface for sending/receiving raw byte sequesnces to the EC, 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. The RTC driver is exposed as a standard RTC 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 v3: - Change <= to >= in mec_in_range() - Add " - EC_HOST_CMD_REGION0" to offset arg for io_bytes_mec() - remove unused ret in probe() - Add newline spacer in probe() - rm unnecessary res in get_resource() - s/8bit/8-bit - rm first sleep when sending command to EC - Move the attribute to the debugfs system - Move the implementation to debugfs.c - Improve the raw hex parsing - Encapsulate global variables in one object - Add safety check when passing less than 3 bytes - Move documentation to debugfs-wilco-ec - explicitly define toplevel_groups from the start, so adding telem later makes sense - Break version attribute into individual attributes - rm unused WILCO_EC_ATTR_RW macro - Moved some #defines from legacy.h to legacy.c - rm #define for driver name - Don't compute weekday when reading from RTC. Still set weekday when writing, as RTC needs this to control advanced power scheduling - rm check for invalid month data - Set range_min and range_max on rtc_device - change err check from "if (ret < 0)" to "if (ret)" - Now bubble up error codes from within sysfs_init() - Add comment that PID means Property ID - rm some useless references to internal docs from documentation - add err check on returned data size - add check on read request offset and size 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 - Remove COMPILE_TEST from Kconfig because inb()/outb() won't work on anything but X86 - Add myself as module author - Tweak mailbox() - Add sysfs documentation - rm duplicate EC_MAILBOX_DATA_SIZE defs - Make docstrings follow kernel style - Fix tags in commit msg - Move Kconfig to subdirectory - Reading raw now includes ASCII translation - 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 when init()ing sysfs - 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 "wilco_ec_event -" prefix from docstring - rm license boiler plate - Add sysfs directory documentation - Fix cosmetics - events are init()ed before subdrivers now - 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 - make format strings in read() and store() functions static Duncan Laurie (6): platform/chrome: Remove cros_ec dependency in lpc_mec platform/chrome: Add new driver for Wilco EC platform/chrome: Add support for raw commands in debugfs platform/chrome: Add sysfs attributes platform/chrome: rtc: Add RTC driver 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 Documentation/ABI/testing/debugfs-wilco-ec | 23 + .../ABI/testing/sysfs-platform-wilco-ec | 196 +++++++ 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 | 47 +- 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 | 154 +++++ drivers/platform/chrome/wilco_ec/debugfs.c | 218 +++++++ drivers/platform/chrome/wilco_ec/event.c | 347 +++++++++++ drivers/platform/chrome/wilco_ec/legacy.c | 103 ++++ drivers/platform/chrome/wilco_ec/legacy.h | 79 +++ drivers/platform/chrome/wilco_ec/mailbox.c | 236 ++++++++ drivers/platform/chrome/wilco_ec/properties.c | 344 +++++++++++ drivers/platform/chrome/wilco_ec/properties.h | 180 ++++++ drivers/platform/chrome/wilco_ec/sysfs.c | 245 ++++++++ drivers/platform/chrome/wilco_ec/telemetry.c | 73 +++ 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 | 177 ++++++ include/linux/platform_data/wilco-ec.h | 189 ++++++ 27 files changed, 3509 insertions(+), 60 deletions(-) create mode 100644 Documentation/ABI/testing/debugfs-wilco-ec create mode 100644 Documentation/ABI/testing/sysfs-platform-wilco-ec 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/debugfs.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 -- 2.20.1.321.g9e740568ce-goog