pinctrl: msm: Add documentation for pinctrl-apq8064 binding

Qualcomm APQ8064 TLMM block

Required properties:

- compatible: "qcom,apq8064-pinctrl"

- reg: Should be the base address and length of the TLMM block.

- interrupts: Should be the parent IRQ of the TLMM block.

- interrupt-controller: Marks the device node as an interrupt controller.

- #interrupt-cells: Should be two.

- gpio-controller: Marks the device node as a GPIO controller.

- #gpio-cells : Should be two.

                The first cell is the gpio pin number and the

                second cell is used for optional parameters.

Please refer to ../gpio/gpio.txt and ../interrupt-controller/interrupts.txt for

a general description of GPIO and interrupt bindings.

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".

Qualcomm's pin configuration nodes act as a container for an abitrary number of

subnodes. Each of these subnodes represents some desired configuration for a

pin, a group, or a list of pins or groups. This configuration can include the

mux function to select on those pin(s)/group(s), and various pin configuration

parameters, such as pull-up, drive strength, etc.

The name of each subnode is not important; all subnodes should be enumerated

and processed purely based on their content.

Each subnode only affects those parameters that are explicitly listed. In

other words, a subnode that lists a mux function but no pin configuration

parameters implies no information about any pin configuration parameters.

Similarly, a pin subnode that describes a pullup parameter implies no

information about e.g. the mux function.

The following generic properties as defined in pinctrl-bindings.txt are valid

to specify in a pin configuration subnode:

 pins, function, bias-disable, bias-pull-down, bias-pull,up, drive-strength,

 output-low, output-high.

Non-empty subnodes must specify the 'pins' property.

Valid values for pins are:

  gpio0-gpio89

Valid values for function are:

  cam_mclk, codec_mic_i2s, codec_spkr_i2s, gsbi1, gsbi2, gsbi3, gsbi4,

  gsbi4_cam_i2c, gsbi5, gsbi5_spi_cs1, gsbi5_spi_cs2, gsbi5_spi_cs3, gsbi6,

  gsbi6_spi_cs1, gsbi6_spi_cs2, gsbi6_spi_cs3, gsbi7, gsbi7_spi_cs1,

  gsbi7_spi_cs2, gsbi7_spi_cs3, gsbi_cam_i2c, hdmi, mi2s, riva_bt, riva_fm,

  riva_wlan, sdc2, sdc4, slimbus, spkr_i2s, tsif1, tsif2, usb2_hsic,

Example:

	msmgpio: pinctrl@800000 {

		compatible = "qcom,apq8064-pinctrl";

		reg = <0x800000 0x4000>;

		gpio-controller;

		#gpio-cells = <2>;

		interrupt-controller;

		#interrupt-cells = <2>;

		interrupts = <0 32 0x4>;

		pinctrl-names = "default";

		pinctrl-0 = <&gsbi5_uart_default>;

		gsbi5_uart_default: gsbi5_uart_default {

			mux {

				pins = "gpio51", "gpio52";

				function = "gsbi5";

			};

			tx {

				pins = "gpio51";

				drive-strength = <4>;

				bias-disable;

			};

			rx {

				pins = "gpio52";

				drive-strength = <2>;

				bias-pull-up;

			};

		};

	};