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>
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