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Julius Werner 2fa9545ac4 gpio: Remove non-ternary tristate mode, make ternaries easier
The function to read board IDs from tristate GPIOs currently supports
two output modes: a normal base-3 integer, or a custom format where
every two bits represent one tristate pin. Each board decides which
representation to use on its own, which is inconsistent and provides
another possible gotcha to trip over when reading unfamiliar code.

The two-bits-per-pin format creates the additional problem that a
complete list of IDs (such as some boards use to build board-ID tables)
necessarily has "holes" in them (since 0b11 does not correspond to a
possible pin state), which makes them extremely tricky to write, read
and expand. It's also very unintuitive in my opinion, although it was
intended to make it easier to read individual pin states from a hex
representation.

This patch switches all boards over to base-3 and removes the other
format to improve consistency. The tristate reading function will just
print the pin states as they are read to make it easier to debug them,
and we add a new BASE3() macro that can generate ternary numbers from
pin states. Also change the order of all static initializers of board ID
pin lists to write the most significant bit first, hoping that this can
help clear up confusion about the endianness of the pins.

CQ-DEPEND=CL:219902
BUG=None
TEST=Booted on a Nyan_Blaze (with board ID 1, unfortunately the only one
I have). Compiled on Daisy, Peach_Pit, Nyan, Nyan_Big, Nyan_Blaze, Rush,
Rush_Ryu, Storm, Veryon_Pinky and Falco for good measure.

Change-Id: I6133cdaf01ed6590ae07e88d9e85a33dc013211a
Signed-off-by: Julius Werner <jwerner@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/219901
Reviewed-by: Aaron Durbin <adurbin@chromium.org>
2014-10-23 01:41:42 +00:00
configs ryu: Change the path of CONFIG_MTS_DIRECTORY 2014-10-22 17:42:01 +00:00
documentation sconfig: rename lapic_cluster -> cpu_cluster 2013-02-14 07:07:20 +01:00
payloads pearlvalley: add board related files for pearlvalley 2014-10-20 08:02:40 +00:00
src gpio: Remove non-ternary tristate mode, make ternaries easier 2014-10-23 01:41:42 +00:00
util timestamp: Add bootblock start and end to timestamp constants 2014-10-17 05:52:39 +00:00
.gitignore rmodules: add support for rmodtool 2014-03-31 22:25:57 +00:00
COMMIT-QUEUE.ini COMMIT-QUEUE.ini: Add documentation. 2013-11-01 14:08:42 +00:00
COPYING update license template. 2006-08-12 22:03:36 +00:00
Makefile Makefile: Change $(generic-deps) to order-only prerequisite 2014-10-04 03:10:51 +00:00
Makefile.inc Change GDB_DEBUG to SOURCE_DEBUG 2014-10-08 05:07:21 +00:00
PRESUBMIT.cfg chromeos: Add PRESUBMIT.cfg 2013-05-01 14:31:10 -07:00
README Update README with newer version of the text from the web page 2011-06-15 10:16:33 +02:00
toolchain.inc arch/mips: Add base MIPS architecture support 2014-09-01 11:05:57 +00:00

-------------------------------------------------------------------------------
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.


Payloads
--------

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

See http://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:

 * http://www.coreboot.org/Supported_Motherboards
 * http://www.coreboot.org/Supported_Chipsets_and_Devices


Build Requirements
------------------

 * gcc / g++
 * make

Optional:

 * doxygen (for generating/viewing documentation)
 * iasl (for targets with ACPI support)
 * gdb (for better debugging facilities on some targets)
 * ncurses (for 'make menuconfig')
 * flex and bison (for regenerating parsers)


Building coreboot
-----------------

Please consult http://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 http://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:

  http://www.coreboot.org

You can contact us directly on the coreboot mailing list:

  http://www.coreboot.org/Mailinglist


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.