mb/google/poppy/variant/atlas: I2C: run trackpad at 1MHz

With this change, coreboot thinks we're running at 1MHz:
	DW I2C bus 2 at 0xd1133000 (1000 KHz)

Elan eKT3644 IC Specification (trackpad) requires:
Low Time  larger than 500ns (61 * 8.3ns = 506ns).
High Time larger than 260ns (32 * 8.3ns = 265ns),
Data Hold_time larger than 0ns.
Start Condition Hold time larger than 250ns.
Rise/Fall time of less than 120ns.

HCNT controls both High Time and Start Condition Hold time.
LCNT controls Low Time.
SDA_HOLD controls Data Hold Time.

P2 Atlas "Rise time" is 90ns and "Fall time" is 32ns and tuned
using resistors on the board and must be considered when
adjusting any of the parameters since these times are all measured
at 30 or 70% of base and peak voltages (0v/1.8v).

The eKT3644 requirements are met with LCNT=69, HCNT=33, SDA_HOLD=20
which yields the SCL at around 950KHz - suboptimal but compliant.

Lower LCNT or HCNT results in "lost arbitration" errors or not complying
with eKT3644 requirements.

Verified by gaggery.tsai@intel.corp-partner.google.com.
Scope shots posted here:

TEST=Farzam provided test points on track pad for SCL/SDA/GND.
     Waveforms measured with oscilloscope and screen shots attached
     to bug (comment #177, #155, #100).
     Operate trackpad/touchscreen
     Review dmesg (kernel) output for correct speed, parameters, and
     no errors (e.g. "lost arbitration" or "host controller timeout")

Change-Id: Iaf42ba7b8818b7cd9c8dcc657823dac705659d38
Signed-off-by: Caveh Jalali <caveh@chromium.org>
Signed-off-by: Grant Grundler <grundler@chromium.org>
Tested-by: gaggery.tsai@intel.corp-partner.google.com
Tested-by: grundler@chromium.org
Reviewed-on: https://review.coreboot.org/29553
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Caveh Jalali <caveh@google.com>
Reviewed-by: Furquan Shaikh <furquan@google.com>
Reviewed-by: Gaggery Tsai <gaggery.tsai@intel.com>
1 file changed
tree: c83d26faa5207e1fa72d324212d9716d5932f0eb
  1. 3rdparty/
  2. configs/
  3. Documentation/
  4. payloads/
  5. src/
  6. util/
  7. .checkpatch.conf
  8. .clang-format
  9. .gitignore
  10. .gitmodules
  11. .gitreview
  13. gnat.adc
  15. Makefile
  16. Makefile.inc
  17. README.md
  18. toolchain.inc

coreboot README

coreboot is a Free Software project aimed at replacing the proprietary BIOS (firmware) found in most computers. coreboot performs a little bit of hardware initialization and then executes additional boot logic, called a payload.

With the separation of hardware initialization and later boot logic, coreboot can scale from specialized applications that run directly firmware, run operating systems in flash, load custom bootloaders, or implement firmware standards, like PC BIOS services or UEFI. This allows for systems to only include the features necessary in the target application, reducing the amount of code and flash space required.

coreboot was formerly known as LinuxBIOS.


After the basic initialization of the hardware has been performed, any desired "payload" can be started by coreboot.

See https://www.coreboot.org/Payloads for a list of supported payloads.

Supported Hardware

coreboot supports a wide range of chipsets, devices, and mainboards.

For details please consult:

Build Requirements

  • make
  • gcc / g++ Because Linux distribution compilers tend to use lots of patches. coreboot does lots of "unusual" things in its build system, some of which break due to those patches, sometimes by gcc aborting, sometimes - and that's worse - by generating broken object code. Two options: use our toolchain (eg. make crosstools-i386) or enable the ANY_TOOLCHAIN Kconfig option if you're feeling lucky (no support in this case).
  • iasl (for targets with ACPI support)
  • pkg-config
  • libssl-dev (openssl)


  • doxygen (for generating/viewing documentation)
  • gdb (for better debugging facilities on some targets)
  • ncurses (for make menuconfig and make nconfig)
  • flex and bison (for regenerating parsers)

Building coreboot

Please consult https://www.coreboot.org/Build_HOWTO for details.

Testing coreboot Without Modifying Your Hardware

If you want to test coreboot without any risks before you really decide to use it on your hardware, you can use the QEMU system emulator to run coreboot virtually in QEMU.

Please see https://www.coreboot.org/QEMU for details.

Website and Mailing List

Further details on the project, a FAQ, many HOWTOs, news, development guidelines and more can be found on the coreboot website:


You can contact us directly on the coreboot mailing list:


Copyright and License

The copyright on coreboot is owned by quite a large number of individual developers and companies. Please check the individual source files for details.

coreboot is licensed under the terms of the GNU General Public License (GPL). Some files are licensed under the "GPL (version 2, or any later version)", and some files are licensed under the "GPL, version 2". For some parts, which were derived from other projects, other (GPL-compatible) licenses may apply. Please check the individual source files for details.

This makes the resulting coreboot images licensed under the GPL, version 2.