fb73d663b3
Add documentation for the pin controller found on the Renesas RZ/V2H(P) (R9A09G057) SoC. The RZ/V2H PFC varies slightly compared to the RZ/G2L family: - Additional bits need to be set during pinmuxing, - The GPIO pin count is different. Hence, a SoC-specific compatible string, 'renesas,r9a09g057-pinctrl', is added for the RZ/V2H(P) SoC. Also, add the 'renesas,output-impedance' property. The drive strength settings on RZ/V2H(P) depend on the different power rails coming out from the PMIC (connected via I2C). These power rails (required for drive strength) can be 1.2V, 1.8V, or 3.3V. Pins are grouped into 4 groups: Group 1: Impedance - 150/75/38/25 ohms (at 3.3V) - 130/65/33/22 ohms (at 1.8V) Group 2: Impedance - 50/40/33/25 ohms (at 1.8V) Group 3: Impedance - 150/75/37.5/25 ohms (at 3.3V) - 130/65/33/22 ohms (at 1.8V) Group 4: Impedance - 110/55/30/20 ohms (at 1.8V) - 150/75/38/25 ohms (at 1.2V) The 'renesas,output-impedance' property, as documented, can be [0, 1, 2, 3], these correspond to register bit values that can be set in the PFC_IOLH_mn register, which adjusts the drive strength value and is pin-dependent. As power rail information may not be available very early in the boot process, the 'renesas,output-impedance' property is added instead of reusing the 'output-impedance-ohms' property. Also, allow bias-disable, bias-pull-down and bias-pull-up properties as these can be used to configure the pins. Signed-off-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@bp.renesas.com> Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be> Reviewed-by: Rob Herring (Arm) <robh@kernel.org> Link: https://lore.kernel.org/r/20240606085133.632307-1-prabhakar.mahadev-lad.rj@bp.renesas.com Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
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 reStructuredText 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.