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Realtek MIPS SoCs (platform name Otto) have GPIO controllers with up to 64 GPIOs, divided over two banks. Each bank has a set of registers for 32 GPIOs, with support for edge-triggered interrupts. Each GPIO bank consists of four 8-bit GPIO ports (ABCD and EFGH). Most registers pack one bit per GPIO, except for the IMR register, which packs two bits per GPIO (AB-CD). Although the byte order is currently assumed to have port A..D at offset 0x0..0x3, this has been observed to be reversed on other, Lexra-based, SoCs (e.g. RTL8196E/97D/97F). Interrupt support is disabled for the fallback devicetree-compatible 'realtek,otto-gpio'. This allows for quick support of GPIO banks in which the byte order would be unknown. In this case, the port ordering in the IMR registers may not match the reversed order in the other registers (DCBA, and BA-DC or DC-BA). Signed-off-by: Sander Vanheule <sander@svanheule.net> Reviewed-by: Linus Walleij <linus.walleij@linaro.org> Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com> Signed-off-by: Bartosz Golaszewski <bgolaszewski@baylibre.com>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.