b82cafad93
The UARTs in the Picasso SoC are memory mapped, but there is also some hardware support that isn't used by any board to make the UARTs behave like the ones found on legacy x86 machines from the 90s. In the MMIO mode the MMIO address of the UART controller is passed to the OS via ACPI. The OS expects the base clock of the UART controller to be 48MHz (see the cz_uart_desc struct in drivers/acpi/acpi_apd.c and drivers/tty/serial/8250/8250_dw.c in the Linux kernel) in this case. It is also possible to enable additional decodes from four 8 byte legacy I/O locations used for serial ports to the different UART controllers, which doesn't disable the MMIO access though. The legacy I/O-mapped serial ports are usually expected to have a base clock of 16*115200Hz which the hardware can also provide to the UART's baud rate generator. So there are two possible valid configurations to use the UARTs; either MMIO access in combination with a 48MHz base clock or the legacy I/O decode with a ~1.8MHz base clock. The existing code unconditionally generates ACPI objects for all enabled UARTs, so those shouldn't be put into legacy mode and switching the base clock to ~1.8MHz was only done in the case that the UART was used as coreboot console UART which still used the MMIO access, but the lower base clock. Since no board even selects this option and it's rather invasive to properly implement this feature, just drop the corresponding broken code. TEST=SoC UART console still works on Mandolin. Change-Id: I26fa8fdfc781b583ba56ac4dbcbbfb6100e84852 Signed-off-by: Felix Held <felix-coreboot@felixheld.de> Reported-by: Kyösti Mälkki <kyosti.malkki@gmail.com> Reviewed-on: https://review.coreboot.org/c/coreboot/+/49371 Reviewed-by: Angel Pons <th3fanbus@gmail.com> Reviewed-by: Kyösti Mälkki <kyosti.malkki@gmail.com> Reviewed-by: Marshall Dawson <marshalldawson3rd@gmail.com> Tested-by: build bot (Jenkins) <no-reply@coreboot.org> |
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| LICENSES | ||
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| payloads | ||
| src | ||
| tests | ||
| util | ||
| .checkpatch.conf | ||
| .clang-format | ||
| .editorconfig | ||
| .gitignore | ||
| .gitmodules | ||
| .gitreview | ||
| AUTHORS | ||
| COPYING | ||
| MAINTAINERS | ||
| Makefile | ||
| Makefile.inc | ||
| README.md | ||
| gnat.adc | ||
| toolchain.inc | ||
README.md
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:
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_TOOLCHAINKconfig 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 menuconfigandmake 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:
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.