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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>
------------------------------------------------------------------------------- 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.