tegrakernel/kernel/kernel-4.9/Documentation/devicetree/bindings/pinctrl/atmel,at91-pinctrl.txt

* Atmel AT91 Pinmux Controller

The AT91 Pinmux Controller, enables the IC
to share one PAD to several functional blocks. The sharing is done by
multiplexing the PAD input/output signals. For each PAD there are up to
8 muxing options (called periph modes). Since different modules require
different PAD settings (like pull up, keeper, etc) the contoller controls
also the PAD settings parameters.

Please refer to pinctrl-bindings.txt in this directory for details of the
common pinctrl bindings used by client devices, including the meaning of the
phrase "pin configuration node".

Atmel AT91 pin configuration node is a node of a group of pins which can be
used for a specific device or function. This node represents both mux and config
of the pins in that group. The 'pins' selects the function mode(also named pin
mode) this pin can work on and the 'config' configures various pad settings
such as pull-up, multi drive, etc.

Required properties for iomux controller:
- compatible: "atmel,at91rm9200-pinctrl" or "atmel,at91sam9x5-pinctrl"
		or "atmel,sama5d3-pinctrl"
- atmel,mux-mask: array of mask (periph per bank) to describe if a pin can be
  configured in this periph mode. All the periph and bank need to be describe.

How to create such array:

Each column will represent the possible peripheral of the pinctrl
Each line will represent a pio bank

Take an example on the 9260
Peripheral: 2 ( A and B)
Bank: 3 (A, B and C)
=>

  /*    A         B     */
  0xffffffff 0xffc00c3b  /* pioA */
  0xffffffff 0x7fff3ccf  /* pioB */
  0xffffffff 0x007fffff  /* pioC */

For each peripheral/bank we will descibe in a u32 if a pin can be
configured in it by putting 1 to the pin bit (1 << pin)

Let's take the pioA on peripheral B
From the datasheet Table 10-2.
Peripheral B
PA0	MCDB0
PA1	MCCDB
PA2
PA3	MCDB3
PA4	MCDB2
PA5	MCDB1
PA6
PA7
PA8
PA9
PA10	ETX2
PA11	ETX3
PA12
PA13
PA14
PA15
PA16
PA17
PA18
PA19
PA20
PA21
PA22	ETXER
PA23	ETX2
PA24	ETX3
PA25	ERX2
PA26	ERX3
PA27	ERXCK
PA28	ECRS
PA29	ECOL
PA30	RXD4
PA31	TXD4

=> 0xffc00c3b

Required properties for pin configuration node:
- atmel,pins: 4 integers array, represents a group of pins mux and config
  setting. The format is atmel,pins = <PIN_BANK PIN_BANK_NUM PERIPH CONFIG>.
  The PERIPH 0 means gpio, PERIPH 1 is periph A, PERIPH 2 is periph B...
  PIN_BANK 0 is pioA, PIN_BANK 1 is pioB...

Bits used for CONFIG:
PULL_UP		(1 << 0): indicate this pin needs a pull up.
MULTIDRIVE	(1 << 1): indicate this pin needs to be configured as multi-drive.
			Multi-drive is equivalent to open-drain type output.
DEGLITCH	(1 << 2): indicate this pin needs deglitch.
PULL_DOWN	(1 << 3): indicate this pin needs a pull down.
DIS_SCHMIT	(1 << 4): indicate this pin needs to the disable schmitt trigger.
DRIVE_STRENGTH (3 << 5): indicate the drive strength of the pin using the
			following values:
				00 - No change (reset state value kept)
				01 - Low
				10 - Medium
				11 - High
DEBOUNCE	(1 << 16): indicate this pin needs debounce.
DEBOUNCE_VAL	(0x3fff << 17): debounce value.

NOTE:
Some requirements for using atmel,at91rm9200-pinctrl binding:
1. We have pin function node defined under at91 controller node to represent
   what pinmux functions this SoC supports.
2. The driver can use the function node's name and pin configuration node's
   name describe the pin function and group hierarchy.
   For example, Linux at91 pinctrl driver takes the function node's name
   as the function name and pin configuration node's name as group name to
   create the map table.
3. Each pin configuration node should have a phandle, devices can set pins
   configurations by referring to the phandle of that pin configuration node.
4. The gpio controller must be describe in the pinctrl simple-bus.

Examples:

pinctrl@fffff400 {
	#address-cells = <1>;
	#size-cells = <1>;
	ranges;
	compatible = "atmel,at91rm9200-pinctrl", "simple-bus";
	reg = <0xfffff400 0x600>;

	atmel,mux-mask = <
	      /*    A         B     */
	       0xffffffff 0xffc00c3b  /* pioA */
	       0xffffffff 0x7fff3ccf  /* pioB */
	       0xffffffff 0x007fffff  /* pioC */
	      >;

	/* shared pinctrl settings */
	dbgu {
		pinctrl_dbgu: dbgu-0 {
			atmel,pins =
				<1 14 0x1 0x0	/* PB14 periph A */
				 1 15 0x1 0x1>;	/* PB15 periph A with pullup */
		};
	};
};

dbgu: serial@fffff200 {
	compatible = "atmel,at91sam9260-usart";
	reg = <0xfffff200 0x200>;
	interrupts = <1 4 7>;
	pinctrl-names = "default";
	pinctrl-0 = <&pinctrl_dbgu>;
	status = "disabled";
};