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regulator: documentation - machine

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This adds documenation describing the regulator machine interface.

Signed-off-by: Liam Girdwood <lg@opensource.wolfsonmicro.com>
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Liam Girdwood 2008-04-30 17:22:50 +01:00
parent e8695ebe55
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Documentation/power/regulator/machine.txt Normal file
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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);