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32da8bed19
The CBMEM console driver saves console output in a CBMEM area, which then is made available to Linux applications for perusing. There are some system limitations which need to be worked around to achieve this goal: - some console traffic is generated before DRAM is initialized, leave alone CBMEM initialized. - after the RAM based stage starts, a lot of traffic is generated before CBMEM is initialized. As a result, the console log lives in three different places - the bottom of the cache as RAM space, the CBMEM buffer (where it is expected to be) and a static buffer used early in the RAM stage. When execution starts (in the cache as RAM mode), the console buffer is allocated at the bottom of the cache as RAM memory address range. Once DRAM is initialized, the CBMEM structure is initialized, and then the console buffer contents are copied from the bottom of the cache as RAM space into the CBMEM area right before the cache as RAM mode is disabled. The src/lib/cbmem_console.c:cbmemc_reinit() takes care of the copying. At this point the cache as RAM memory is about to be disabled, but the ROM stage is still going generating console output. To make sure this output is not lost, cbmemc_reinit() saves the new buffer address at a fixed location (0x600 was chosen for this), and the actual "printing" function checks to see if the RAM is already initialized (the stack is in RAM), and if so, gets the console buffer pointer from this location instead of using the cache as RAM address. When the RAM stage starts, a static buffer is used to store the console output, as the CBMEM buffer location is not known. Then, when CBMEM is reinitialized, cbmemc_reinit() again takes care of the copying. In case the allocated buffers are not large enough, the excessive data is dropped, and the copying routine adds some text to the output buffer to indicate that there has been data lost and how many characters were dropped. Change-Id: I8c126e31db6cb2141f7f4f97c5047f39a8db44fc Signed-off-by: Vadim Bendebury <vbendeb@chromium.org> Reviewed-on: http://review.coreboot.org/719 Tested-by: build bot (Jenkins) Reviewed-by: Ronald G. Minnich <rminnich@gmail.com> |
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| 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 ------------------ * 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.