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Julius Werner 99f4683adf Introduce bootblock self-decompression
Masked ROMs are the silent killers of boot speed on devices without
memory-mapped SPI flash. They often contain awfully slow SPI drivers
(presumably bit-banged) that take hundreds of milliseconds to load our
bootblock, and every extra kilobyte of bootblock size has a hugely
disproportionate impact on boot speed. The coreboot timestamps can never
show that component, but it impacts our users all the same.

This patch tries to alleviate that issue a bit by allowing us to
compress the bootblock with LZ4, which can cut its size down to nearly
half. Of course, masked ROMs usually don't come with decompression
algorithms built in, so we need to introduce a little decompression stub
that can decompress the rest of the bootblock. This is done by creating
a new "decompressor" stage which runs before the bootblock, but includes
the compressed bootblock code in its data section. It needs to be as
small as possible to get a real benefit from this approach, which means
no device drivers, no console output, no exception handling, etc.
Besides the decompression algorithm itself we only include the timer
driver so that we can measure the boot speed impact of decompression. On
ARM and ARM64 systems, we also need to give SoC code a chance to
initialize the MMU, since running decompression without MMU is
prohibitively slow on these architectures.

This feature is implemented for ARM and ARM64 architectures for now,
although most of it is architecture-independent and it should be
relatively simple to port to other platforms where a masked ROM loads
the bootblock into SRAM. It is also supposed to be a clean starting
point from which later optimizations can hopefully cut down the
decompression stub size (currently ~4K on RK3399) a bit more.

NOTE: Bootblock compression is not for everyone. Possible side effects
include trying to run LZ4 on CPUs that come out of reset extremely
underclocked or enabling this too early in SoC bring-up and getting
frustrated trying to find issues in an undebuggable environment. Ask
your SoC vendor if bootblock compression is right for you.

Change-Id: I0dc1cad9ae7508892e477739e743cd1afb5945e8
Signed-off-by: Julius Werner <jwerner@chromium.org>
Reviewed-on: https://review.coreboot.org/26340
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Aaron Durbin <adurbin@chromium.org>
2018-05-22 02:44:14 +00:00
3rdparty 3rdparty/blobs: Update submodule marker for Intel microcode updates 2018-05-15 13:19:19 +00:00
Documentation Documentation: Add lesson1 from the wiki 2018-05-20 19:12:52 +00:00
configs configs: add PC Engines apu2 sample configuration 2018-05-19 16:55:56 +00:00
payloads libpayload: Fix payload .bss corruption 2018-05-21 04:48:28 +00:00
src Introduce bootblock self-decompression 2018-05-22 02:44:14 +00:00
util cbfs-compression-tool: Add raw compression support 2018-05-22 02:38:35 +00:00
.checkpatch.conf .checkpatch.conf: Ignore CORRUPTED_PATCH lint 2017-10-29 10:11:58 +00:00
.clang-format clang-format: Update .clang-format to be compliant with linux kernel coding style 2018-04-23 09:26:08 +00:00
.gitignore Documentation: Add support for building with Sphinx 2018-04-26 12:25:03 +00:00
.gitmodules Set up 3rdparty/libgfxinit 2016-10-29 01:35:03 +02:00
.gitreview
COPYING
MAINTAINERS MAINTAINERS: change second PC Engines maintainer 2018-03-21 18:25:49 +00:00
Makefile Makefile: Add filelist to help 2018-01-29 15:35:11 +00:00
Makefile.inc Introduce bootblock self-decompression 2018-05-22 02:44:14 +00:00
README README: Update requirements 2017-06-27 17:04:32 +00:00
gnat.adc gnat.adc: Do not generate assertion code for Refined_Post 2016-10-29 01:33:31 +02:00
toolchain.inc Introduce bootblock self-decompression 2018-05-22 02:44:14 +00:00

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 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:

 * https://www.coreboot.org/Supported_Motherboards
 * https://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)
 * pkg-config
 * libssl-dev (openssl)

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 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:

  https://www.coreboot.org

You can contact us directly on the coreboot mailing list:

  https://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.