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Aaron Durbin 7f8afe0631 arch/x86: introduce postcar stage/phase
Certain chipsets don't have a memory-mapped boot media
so their code execution for stages prior to DRAM initialization
is backed by SRAM or cache-as-ram. The postcar stage/phase
handles the cache-as-ram situation where in order to tear down
cache-as-ram one needs to be executing out of a backing
store that isn't transient. By current definition, cache-as-ram
is volatile and tearing it down leads to its contents disappearing.
Therefore provide a shim layer, postcar, that's loaded into
memory and executed which does 2 things:

1. Tears down cache-as-ram with a chipset helper function.
2. Loads and runs ramstage.

Because those 2 things are executed out of ram there's no issue
of the code's backing store while executing the code that
tears down cache-as-ram. The current implementation makes no
assumption regarding cacheability of the DRAM itself. If the
chipset code wishes to cache DRAM for loading of the postcar
stage/phase then it's also up to the chipset to handle any
coherency issues pertaining to cache-as-ram destruction.

Change-Id: Ia58efdadd0b48f20cfe7de2f49ab462306c3a19b
Signed-off-by: Aaron Durbin <adurbin@chromium.org>
Reviewed-on: https://review.coreboot.org/14140
Tested-by: build bot (Jenkins)
Reviewed-by: Patrick Georgi <pgeorgi@google.com>
Reviewed-by: Furquan Shaikh <furquan@google.com>
2016-03-23 14:24:30 +01:00
3rdparty vboot: Update to current master to support S3 resume signalling 2016-02-29 20:19:06 +01:00
Documentation Documentation: x86 MTRR setup, TempRamExit and MTRR loading 2016-03-21 20:12:35 +01:00
payloads payloads: Add a target to print payload git urls and directories 2016-03-21 14:32:02 +01:00
src arch/x86: introduce postcar stage/phase 2016-03-23 14:24:30 +01:00
util rockchip: update make_idb.py 2016-03-16 15:24:10 +01:00
.clang-format Provide coreboot coding style formalisation file for clang-format 2015-11-10 00:49:03 +01:00
.gitignore payloads: Enable building depthcharge as part of the coreboot build 2016-03-15 21:18:22 +01:00
.gitmodules git modules: rename git submodules to avoid hierarchies 2016-02-11 20:55:55 +01:00
.gitreview
COPYING
MAINTAINERS MAINTAINERS: Add maintainer for Braswell SOC & Reference board 2016-03-22 19:58:35 +01:00
Makefile Makefile: Update payload clean targets 2016-03-09 17:01:56 +01:00
Makefile.inc arch/x86: introduce postcar stage/phase 2016-03-23 14:24:30 +01:00
README
toolchain.inc toolchain.inc: test IASL by version string instead of number 2016-03-04 16:36:25 +01:00

README

-------------------------------------------------------------------------------
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
------------------

 * 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)

Optional:

 * 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 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.