regulator: pwm-regulator: Re-write bindings

pwm regulator bindings

Bindings for the Generic PWM Regulator

======================================

Currently supports 2 modes of operation:

voltage-table:		When in this mode, a voltage table (See below) of

			predefined voltage <=> duty-cycle values must be

			provided via DT. Limitations are that the regulator can

			only operate at the voltages supplied in the table.

			Intermediary duty-cycle values which would normally

			allow finer grained voltage selection are ignored and

			rendered useless.  Although more control is given to

			the user if the assumptions made in continuous-voltage

			mode do not reign true.

continuous-voltage:	This mode uses the regulator's maximum and minimum

			supplied voltages specified in the

			regulator-{min,max}-microvolt properties to calculate

			appropriate duty-cycle values.  This allows for a much

			more fine grained solution when compared with

			voltage-table mode above.  This solution does make an

			assumption that a %50 duty-cycle value will cause the

			regulator voltage to run at half way between the

			supplied max_uV and min_uV values.

Required properties:

--------------------

- compatible:		Should be "pwm-regulator"

- pwms: OF device-tree PWM specification (see PWM binding pwm.txt)

- voltage-table: voltage and duty table, include 2 members in each set of

  brackets, first one is voltage(unit: uv), the next is duty(unit: percent)

Any property defined as part of the core regulator binding defined in

regulator.txt can also be used.

- pwms:			PWM specification (See: ../pwm/pwm.txt)

One of these must be provided:

- voltage-table: 	Voltage and Duty-Cycle table consisting of 2 cells

			    First cell is voltage in microvolts (uV)

			    Second cell is duty-cycle in percent (%)

- max-duty-cycle:	Maximum Duty-Cycle value -- this will normally be

  			255 (0xff) for an 8 bit PWM device

If both are provided, the current default is voltage-table mode.

Example:

Any property defined as part of the core regulator binding can also be used.

(See: ../regulator/regulator.txt)

Continuous Voltage Example:

	pwm_regulator {

		compatible = "pwm-regulator;

		pwms = <&pwm1 0 8448 0>;

		regulator-min-microvolt = <1016000>;

		regulator-max-microvolt = <1114000>;

		regulator-name = "vdd_logic";

		max-duty-cycle = <255>; /* 8bit PWM */

	};

Voltage Table Example:

	pwm_regulator {

		compatible = "pwm-regulator;

		pwms = <&pwm1 0 8448 0>;

		regulator-min-microvolt = <1016000>;

		regulator-max-microvolt = <1114000>;

		regulator-name = "vdd_logic";

			      /* Voltage Duty-Cycle */

		voltage-table = <1114000 0>,

				<1095000 10>,

				<1076000 20>,

				<1056000 30>,

				<1036000 40>,

				<1016000 50>;

		regulator-min-microvolt = <1016000>;

		regulator-max-microvolt = <1114000>;

		regulator-name = "vdd_logic";

	};