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08d5a89fd0
The pins on tegra are controlled by three different units, the pinmux, the pin group controls, and the GPIO banks. Each of these units controls some aspect of the pins, and they layer together and interact in interesting ways. By default, the GPIOs are configured to pass through the special purpose IO that the pinmux is configured to and so can be ignored unless a GPIO is needed. The pinmux controls which special purpose signal passes through, along with pull ups, downs, and whether the output is tristated. The pingroup controls change the parameters of a group of pins which all have to do with a related function unit. The enum which holds constants related to the pinmux is relatively involved and may not be entirely complete or correct due to slightly inconsistent, incomplete, or missing documentation related to the pinmux. Considerable effort has been made to make it as accurate as possible. It includes a constant which is the index into the pinmux control registers for that pin, what each of the functions supported by that pin are, and which GPIO it corresponds to. The GPIO constant is named after the GPIO and is the pinmux register index for the pin for that GPIO. That way, when you need to turn on a GPIO, you can use that constant along with the pinmux manipulating functions to enable its tristate and pull up/down mode in addition to setting up the GPIO controls. Also, while in general I prefer not to use macros or the preprocessor when writing C code, in this case the set of constants in the enums was too large and cumbersome to manage without them. Since they're being used to construct a table in a straightforward way, hopefully their negative aspects will be minimized. In addition to the low level functions in each driver, the GPIO code also includes some high level functions to set up input or output GPIOs since that will probably be a very common thing to want to do. Old-Change-Id: I48efa58d1b5520c0367043cef76b6d3a7a18530d Signed-off-by: Gabe Black <gabeblack@google.com> Reviewed-on: https://chromium-review.googlesource.com/171806 Reviewed-by: Ronald Minnich <rminnich@chromium.org> Reviewed-by: David Hendricks <dhendrix@chromium.org> Commit-Queue: Gabe Black <gabeblack@chromium.org> Tested-by: Gabe Black <gabeblack@chromium.org> (cherry picked from commit 5cd9f17fe0196d13c1e10b8cde0f2d3989b5ae1a) tegra124: Add base address for the pinmux and pingroup registers. There weren't any constants for the pinmux or pingroup registers in the address map header. Old-Change-Id: I52b9042c7506cab0bedd7a734f346cc9fe4ac3fe Signed-off-by: Gabe Black <gabeblack@google.com> Reviewed-on: https://chromium-review.googlesource.com/172081 Reviewed-by: Julius Werner <jwerner@chromium.org> Tested-by: Gabe Black <gabeblack@chromium.org> Commit-Queue: Gabe Black <gabeblack@chromium.org> (cherry picked from commit 79b61016bfd702b0ea5221658305d8bd359f4f62) Squashed two related commits. Change-Id: Ifeb6085128bd53f0ef5f82c930eda66a2b59499b Signed-off-by: Isaac Christensen <isaac.christensen@se-eng.com> Reviewed-on: http://review.coreboot.org/6702 Tested-by: build bot (Jenkins) |
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------------------------------------------------------------------------------- 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.