Documentation/power/regulator/machine.txt

Regulator Machine Driver Interface
===================================

The regulator machine driver interface is intended for board/machine specific
initialisation code to configure the regulator subsystem. Typical things that
machine drivers would do are :-

 1. Regulator -> Device mapping.
 2. Regulator supply configuration.
 3. Power Domain constraint setting.



1. Regulator -> device mapping
==============================
Consider the following machine :-

  Regulator-1 -+-> Regulator-2 --> [Consumer A @ 1.8 - 2.0V]
               |
               +-> [Consumer B @ 3.3V]

The drivers for consumers A & B must be mapped to the correct regulator in
order to control their power supply. This mapping can be achieved in machine
initialisation code by calling :-

int regulator_set_device_supply(const char *regulator, struct device *dev,
				const char *supply);

and is shown with the following code :-

regulator_set_device_supply("Regulator-1", devB, "Vcc");
regulator_set_device_supply("Regulator-2", devA, "Vcc");

This maps Regulator-1 to the 'Vcc' supply for Consumer B and maps Regulator-2
to the 'Vcc' supply for Consumer A.


2. Regulator supply configuration.
==================================
Consider the following machine (again) :-

  Regulator-1 -+-> Regulator-2 --> [Consumer A @ 1.8 - 2.0V]
               |
               +-> [Consumer B @ 3.3V]

Regulator-1 supplies power to Regulator-2. This relationship must be registered
with the core so that Regulator-1 is also enabled when Consumer A enables it's
supply (Regulator-2).

This relationship can be register with the core via :-

int regulator_set_supply(const char *regulator, const char *regulator_supply);

In this example we would use the following code :-

regulator_set_supply("Regulator-2", "Regulator-1");

Relationships can be queried by calling :-

const char *regulator_get_supply(const char *regulator);


3. Power Domain constraint setting.
===================================
Each power domain within a system has physical constraints on voltage and
current. This must be defined in software so that the power domain is always
operated within specifications.

Consider the following machine (again) :-

  Regulator-1 -+-> Regulator-2 --> [Consumer A @ 1.8 - 2.0V]
               |
               +-> [Consumer B @ 3.3V]

This gives us two regulators and two power domains:

                   Domain 1: Regulator-2, Consumer B.
                   Domain 2: Consumer A.

Constraints can be registered by calling :-

int regulator_set_platform_constraints(const char *regulator,
	struct regulation_constraints *constraints);

The example is defined as follows :-

struct regulation_constraints domain_1 = {
	.min_uV = 3300000,
	.max_uV = 3300000,
	.valid_modes_mask = REGULATOR_MODE_NORMAL,
};

struct regulation_constraints domain_2 = {
	.min_uV = 1800000,
	.max_uV = 2000000,
	.valid_ops_mask = REGULATOR_CHANGE_VOLTAGE,
	.valid_modes_mask = REGULATOR_MODE_NORMAL,
};

regulator_set_platform_constraints("Regulator-1", &domain_1);
regulator_set_platform_constraints("Regulator-2", &domain_2);