Re: [PATCH v3 0/9] platform/chrome: rtc: Add support for Wilco EC

[Enric Balletbo Serra]

Hi Nick,

Missatge de Nick Crews <ncrews@xxxxxxxxxxxx> del dia ds., 19 de gen.
2019 a les 1:17:
>
>
> 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.
>

I reviewed some patches of these series and I think that some of them
are already close to be accepted, however, I still have several doubts
regarding the bunch of sysfs attributes/properties. It is clear for me
that some of them (like the version ones) fit into the sysfs, but I
have several doubts with the power and telemetry attributes, looks to
me that we're abusing of the sysfs interface. I am wondering if
wouldn't be better use a simple ioctl functions that reads and writes
to a chardev (/dev/wilco_ec). Did you think on that possibility? What
people think?

Thanks,
 Enric

> 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
>