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Solving the DACR bug will mean that XN bits suddenly become enforced on non-LPAE systems, and we will no longer be able to execute out of a region mapped DCACHE_OFF. When we enable the MMU in romstage we are still executing out of SRAM, so we would instantly kill ourselves. Solve this issue by enabling the MMU earlier (in the bootblock) and mapping the SRAM regions as DCACHE_WRITETHROUGH. They should really be DCACHE_WRITEBACK, but it looks like there might be hardware limitations in the Cortex-A12 cache architecture that prevent us from doing so. Write-through mappings are equivalent to normal non-cacheable on the A12 anyway, and by using this attribute we don't need to introduce a new DCACHE_OFF_BUT_WITHOUT_XN_BIT type in our API. (Also, using normal non-cacheable might still have a slight speed advantage over strongly ordered since it should fetch whole cache lines at once if the processor finds enough accesses it can combine.) CQ-DEPEND=CL:223783 BUG=chrome-os-partner:32118 TEST=None (depends on follow-up CL) Change-Id: I1e5127421f82177ca11af892b1539538b379625e Signed-off-by: Patrick Georgi <pgeorgi@chromium.org> Original-Commit-Id: e7b079f4b6a69449f3c7cc18ef0e1704f2006847 Original-Change-Id: I53e827d95acc2db909f1251de78d65e295eceaa7 Original-Signed-off-by: Julius Werner <jwerner@chromium.org> Original-Reviewed-on: https://chromium-review.googlesource.com/223782 Original-Reviewed-by: Aaron Durbin <adurbin@chromium.org> Reviewed-on: http://review.coreboot.org/9342 Tested-by: build bot (Jenkins) Reviewed-by: Stefan Reinauer <stefan.reinauer@coreboot.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 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.