diff options
Diffstat (limited to 'kernel/Documentation/power/regulator')
| -rw-r--r-- | kernel/Documentation/power/regulator/consumer.txt | 218 | ||||
| -rw-r--r-- | kernel/Documentation/power/regulator/design.txt | 33 | ||||
| -rw-r--r-- | kernel/Documentation/power/regulator/machine.txt | 100 | ||||
| -rw-r--r-- | kernel/Documentation/power/regulator/overview.txt | 171 | ||||
| -rw-r--r-- | kernel/Documentation/power/regulator/regulator.txt | 30 |
5 files changed, 552 insertions, 0 deletions
diff --git a/kernel/Documentation/power/regulator/consumer.txt b/kernel/Documentation/power/regulator/consumer.txt new file mode 100644 index 000000000..e51564c1a --- /dev/null +++ b/kernel/Documentation/power/regulator/consumer.txt @@ -0,0 +1,218 @@ +Regulator Consumer Driver Interface +=================================== + +This text describes the regulator interface for consumer device drivers. +Please see overview.txt for a description of the terms used in this text. + + +1. Consumer Regulator Access (static & dynamic drivers) +======================================================= + +A consumer driver can get access to its supply regulator by calling :- + +regulator = regulator_get(dev, "Vcc"); + +The consumer passes in its struct device pointer and power supply ID. The core +then finds the correct regulator by consulting a machine specific lookup table. +If the lookup is successful then this call will return a pointer to the struct +regulator that supplies this consumer. + +To release the regulator the consumer driver should call :- + +regulator_put(regulator); + +Consumers can be supplied by more than one regulator e.g. codec consumer with +analog and digital supplies :- + +digital = regulator_get(dev, "Vcc"); /* digital core */ +analog = regulator_get(dev, "Avdd"); /* analog */ + +The regulator access functions regulator_get() and regulator_put() will +usually be called in your device drivers probe() and remove() respectively. + + +2. Regulator Output Enable & Disable (static & dynamic drivers) +==================================================================== + +A consumer can enable its power supply by calling:- + +int regulator_enable(regulator); + +NOTE: The supply may already be enabled before regulator_enabled() is called. +This may happen if the consumer shares the regulator or the regulator has been +previously enabled by bootloader or kernel board initialization code. + +A consumer can determine if a regulator is enabled by calling :- + +int regulator_is_enabled(regulator); + +This will return > zero when the regulator is enabled. + + +A consumer can disable its supply when no longer needed by calling :- + +int regulator_disable(regulator); + +NOTE: This may not disable the supply if it's shared with other consumers. The +regulator will only be disabled when the enabled reference count is zero. + +Finally, a regulator can be forcefully disabled in the case of an emergency :- + +int regulator_force_disable(regulator); + +NOTE: this will immediately and forcefully shutdown the regulator output. All +consumers will be powered off. + + +3. Regulator Voltage Control & Status (dynamic drivers) +====================================================== + +Some consumer drivers need to be able to dynamically change their supply +voltage to match system operating points. e.g. CPUfreq drivers can scale +voltage along with frequency to save power, SD drivers may need to select the +correct card voltage, etc. + +Consumers can control their supply voltage by calling :- + +int regulator_set_voltage(regulator, min_uV, max_uV); + +Where min_uV and max_uV are the minimum and maximum acceptable voltages in +microvolts. + +NOTE: this can be called when the regulator is enabled or disabled. If called +when enabled, then the voltage changes instantly, otherwise the voltage +configuration changes and the voltage is physically set when the regulator is +next enabled. + +The regulators configured voltage output can be found by calling :- + +int regulator_get_voltage(regulator); + +NOTE: get_voltage() will return the configured output voltage whether the +regulator is enabled or disabled and should NOT be used to determine regulator +output state. However this can be used in conjunction with is_enabled() to +determine the regulator physical output voltage. + + +4. Regulator Current Limit Control & Status (dynamic drivers) +=========================================================== + +Some consumer drivers need to be able to dynamically change their supply +current limit to match system operating points. e.g. LCD backlight driver can +change the current limit to vary the backlight brightness, USB drivers may want +to set the limit to 500mA when supplying power. + +Consumers can control their supply current limit by calling :- + +int regulator_set_current_limit(regulator, min_uA, max_uA); + +Where min_uA and max_uA are the minimum and maximum acceptable current limit in +microamps. + +NOTE: this can be called when the regulator is enabled or disabled. If called +when enabled, then the current limit changes instantly, otherwise the current +limit configuration changes and the current limit is physically set when the +regulator is next enabled. + +A regulators current limit can be found by calling :- + +int regulator_get_current_limit(regulator); + +NOTE: get_current_limit() will return the current limit whether the regulator +is enabled or disabled and should not be used to determine regulator current +load. + + +5. Regulator Operating Mode Control & Status (dynamic drivers) +============================================================= + +Some consumers can further save system power by changing the operating mode of +their supply regulator to be more efficient when the consumers operating state +changes. e.g. consumer driver is idle and subsequently draws less current + +Regulator operating mode can be changed indirectly or directly. + +Indirect operating mode control. +-------------------------------- +Consumer drivers can request a change in their supply regulator operating mode +by calling :- + +int regulator_set_load(struct regulator *regulator, int load_uA); + +This will cause the core to recalculate the total load on the regulator (based +on all its consumers) and change operating mode (if necessary and permitted) +to best match the current operating load. + +The load_uA value can be determined from the consumer's datasheet. e.g. most +datasheets have tables showing the maximum current consumed in certain +situations. + +Most consumers will use indirect operating mode control since they have no +knowledge of the regulator or whether the regulator is shared with other +consumers. + +Direct operating mode control. +------------------------------ +Bespoke or tightly coupled drivers may want to directly control regulator +operating mode depending on their operating point. This can be achieved by +calling :- + +int regulator_set_mode(struct regulator *regulator, unsigned int mode); +unsigned int regulator_get_mode(struct regulator *regulator); + +Direct mode will only be used by consumers that *know* about the regulator and +are not sharing the regulator with other consumers. + + +6. Regulator Events +=================== +Regulators can notify consumers of external events. Events could be received by +consumers under regulator stress or failure conditions. + +Consumers can register interest in regulator events by calling :- + +int regulator_register_notifier(struct regulator *regulator, + struct notifier_block *nb); + +Consumers can unregister interest by calling :- + +int regulator_unregister_notifier(struct regulator *regulator, + struct notifier_block *nb); + +Regulators use the kernel notifier framework to send event to their interested +consumers. + +7. Regulator Direct Register Access +=================================== +Some kinds of power management hardware or firmware are designed such that +they need to do low-level hardware access to regulators, with no involvement +from the kernel. Examples of such devices are: + +- clocksource with a voltage-controlled oscillator and control logic to change + the supply voltage over I2C to achieve a desired output clock rate +- thermal management firmware that can issue an arbitrary I2C transaction to + perform system poweroff during overtemperature conditions + +To set up such a device/firmware, various parameters like I2C address of the +regulator, addresses of various regulator registers etc. need to be configured +to it. The regulator framework provides the following helpers for querying +these details. + +Bus-specific details, like I2C addresses or transfer rates are handled by the +regmap framework. To get the regulator's regmap (if supported), use :- + +struct regmap *regulator_get_regmap(struct regulator *regulator); + +To obtain the hardware register offset and bitmask for the regulator's voltage +selector register, use :- + +int regulator_get_hardware_vsel_register(struct regulator *regulator, + unsigned *vsel_reg, + unsigned *vsel_mask); + +To convert a regulator framework voltage selector code (used by +regulator_list_voltage) to a hardware-specific voltage selector that can be +directly written to the voltage selector register, use :- + +int regulator_list_hardware_vsel(struct regulator *regulator, + unsigned selector); diff --git a/kernel/Documentation/power/regulator/design.txt b/kernel/Documentation/power/regulator/design.txt new file mode 100644 index 000000000..fdd919b96 --- /dev/null +++ b/kernel/Documentation/power/regulator/design.txt @@ -0,0 +1,33 @@ +Regulator API design notes +========================== + +This document provides a brief, partially structured, overview of some +of the design considerations which impact the regulator API design. + +Safety +------ + + - Errors in regulator configuration can have very serious consequences + for the system, potentially including lasting hardware damage. + - It is not possible to automatically determine the power configuration + of the system - software-equivalent variants of the same chip may + have different power requirements, and not all components with power + requirements are visible to software. + + => The API should make no changes to the hardware state unless it has + specific knowledge that these changes are safe to perform on this + particular system. + +Consumer use cases +------------------ + + - The overwhelming majority of devices in a system will have no + requirement to do any runtime configuration of their power beyond + being able to turn it on or off. + + - Many of the power supplies in the system will be shared between many + different consumers. + + => The consumer API should be structured so that these use cases are + very easy to handle and so that consumers will work with shared + supplies without any additional effort. diff --git a/kernel/Documentation/power/regulator/machine.txt b/kernel/Documentation/power/regulator/machine.txt new file mode 100644 index 000000000..757e3b53d --- /dev/null +++ b/kernel/Documentation/power/regulator/machine.txt @@ -0,0 +1,100 @@ +Regulator Machine Driver Interface +=================================== + +The regulator machine driver interface is intended for board/machine specific +initialisation code to configure the regulator subsystem. + +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 supplies. This mapping can be achieved in machine +initialisation code by creating a struct regulator_consumer_supply for +each regulator. + +struct regulator_consumer_supply { + const char *dev_name; /* consumer dev_name() */ + const char *supply; /* consumer supply - e.g. "vcc" */ +}; + +e.g. for the machine above + +static struct regulator_consumer_supply regulator1_consumers[] = { +{ + .dev_name = "dev_name(consumer B)", + .supply = "Vcc", +},}; + +static struct regulator_consumer_supply regulator2_consumers[] = { +{ + .dev = "dev_name(consumer A"), + .supply = "Vcc", +},}; + +This maps Regulator-1 to the 'Vcc' supply for Consumer B and maps Regulator-2 +to the 'Vcc' supply for Consumer A. + +Constraints can now be registered by defining a struct regulator_init_data +for each regulator power domain. This structure also maps the consumers +to their supply regulators :- + +static struct regulator_init_data regulator1_data = { + .constraints = { + .name = "Regulator-1", + .min_uV = 3300000, + .max_uV = 3300000, + .valid_modes_mask = REGULATOR_MODE_NORMAL, + }, + .num_consumer_supplies = ARRAY_SIZE(regulator1_consumers), + .consumer_supplies = regulator1_consumers, +}; + +The name field should be set to something that is usefully descriptive +for the board for configuration of supplies for other regulators and +for use in logging and other diagnostic output. Normally the name +used for the supply rail in the schematic is a good choice. If no +name is provided then the subsystem will choose one. + +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 its +supply (Regulator-2). The supply regulator is set by the supply_regulator +field below and co:- + +static struct regulator_init_data regulator2_data = { + .supply_regulator = "Regulator-1", + .constraints = { + .min_uV = 1800000, + .max_uV = 2000000, + .valid_ops_mask = REGULATOR_CHANGE_VOLTAGE, + .valid_modes_mask = REGULATOR_MODE_NORMAL, + }, + .num_consumer_supplies = ARRAY_SIZE(regulator2_consumers), + .consumer_supplies = regulator2_consumers, +}; + +Finally the regulator devices must be registered in the usual manner. + +static struct platform_device regulator_devices[] = { +{ + .name = "regulator", + .id = DCDC_1, + .dev = { + .platform_data = ®ulator1_data, + }, +}, +{ + .name = "regulator", + .id = DCDC_2, + .dev = { + .platform_data = ®ulator2_data, + }, +}, +}; +/* register regulator 1 device */ +platform_device_register(®ulator_devices[0]); + +/* register regulator 2 device */ +platform_device_register(®ulator_devices[1]); diff --git a/kernel/Documentation/power/regulator/overview.txt b/kernel/Documentation/power/regulator/overview.txt new file mode 100644 index 000000000..40ca2d6e2 --- /dev/null +++ b/kernel/Documentation/power/regulator/overview.txt @@ -0,0 +1,171 @@ +Linux voltage and current regulator framework +============================================= + +About +===== + +This framework is designed to provide a standard kernel interface to control +voltage and current regulators. + +The intention is to allow systems to dynamically control regulator power output +in order to save power and prolong battery life. This applies to both voltage +regulators (where voltage output is controllable) and current sinks (where +current limit is controllable). + +(C) 2008 Wolfson Microelectronics PLC. +Author: Liam Girdwood <lrg@slimlogic.co.uk> + + +Nomenclature +============ + +Some terms used in this document:- + + o Regulator - Electronic device that supplies power to other devices. + Most regulators can enable and disable their output whilst + some can control their output voltage and or current. + + Input Voltage -> Regulator -> Output Voltage + + + o PMIC - Power Management IC. An IC that contains numerous regulators + and often contains other subsystems. + + + o Consumer - Electronic device that is supplied power by a regulator. + Consumers can be classified into two types:- + + Static: consumer does not change its supply voltage or + current limit. It only needs to enable or disable its + power supply. Its supply voltage is set by the hardware, + bootloader, firmware or kernel board initialisation code. + + Dynamic: consumer needs to change its supply voltage or + current limit to meet operation demands. + + + o Power Domain - Electronic circuit that is supplied its input power by the + output power of a regulator, switch or by another power + domain. + + The supply regulator may be behind a switch(s). i.e. + + Regulator -+-> Switch-1 -+-> Switch-2 --> [Consumer A] + | | + | +-> [Consumer B], [Consumer C] + | + +-> [Consumer D], [Consumer E] + + That is one regulator and three power domains: + + Domain 1: Switch-1, Consumers D & E. + Domain 2: Switch-2, Consumers B & C. + Domain 3: Consumer A. + + and this represents a "supplies" relationship: + + Domain-1 --> Domain-2 --> Domain-3. + + A power domain may have regulators that are supplied power + by other regulators. i.e. + + Regulator-1 -+-> Regulator-2 -+-> [Consumer A] + | + +-> [Consumer B] + + This gives us two regulators and two power domains: + + Domain 1: Regulator-2, Consumer B. + Domain 2: Consumer A. + + and a "supplies" relationship: + + Domain-1 --> Domain-2 + + + o Constraints - Constraints are used to define power levels for performance + and hardware protection. Constraints exist at three levels: + + Regulator Level: This is defined by the regulator hardware + operating parameters and is specified in the regulator + datasheet. i.e. + + - voltage output is in the range 800mV -> 3500mV. + - regulator current output limit is 20mA @ 5V but is + 10mA @ 10V. + + Power Domain Level: This is defined in software by kernel + level board initialisation code. It is used to constrain a + power domain to a particular power range. i.e. + + - Domain-1 voltage is 3300mV + - Domain-2 voltage is 1400mV -> 1600mV + - Domain-3 current limit is 0mA -> 20mA. + + Consumer Level: This is defined by consumer drivers + dynamically setting voltage or current limit levels. + + e.g. a consumer backlight driver asks for a current increase + from 5mA to 10mA to increase LCD illumination. This passes + to through the levels as follows :- + + Consumer: need to increase LCD brightness. Lookup and + request next current mA value in brightness table (the + consumer driver could be used on several different + personalities based upon the same reference device). + + Power Domain: is the new current limit within the domain + operating limits for this domain and system state (e.g. + battery power, USB power) + + Regulator Domains: is the new current limit within the + regulator operating parameters for input/output voltage. + + If the regulator request passes all the constraint tests + then the new regulator value is applied. + + +Design +====== + +The framework is designed and targeted at SoC based devices but may also be +relevant to non SoC devices and is split into the following four interfaces:- + + + 1. Consumer driver interface. + + This uses a similar API to the kernel clock interface in that consumer + drivers can get and put a regulator (like they can with clocks atm) and + get/set voltage, current limit, mode, enable and disable. This should + allow consumers complete control over their supply voltage and current + limit. This also compiles out if not in use so drivers can be reused in + systems with no regulator based power control. + + See Documentation/power/regulator/consumer.txt + + 2. Regulator driver interface. + + This allows regulator drivers to register their regulators and provide + operations to the core. It also has a notifier call chain for propagating + regulator events to clients. + + See Documentation/power/regulator/regulator.txt + + 3. Machine interface. + + This interface is for machine specific code and allows the creation of + voltage/current domains (with constraints) for each regulator. It can + provide regulator constraints that will prevent device damage through + overvoltage or overcurrent caused by buggy client drivers. It also + allows the creation of a regulator tree whereby some regulators are + supplied by others (similar to a clock tree). + + See Documentation/power/regulator/machine.txt + + 4. Userspace ABI. + + The framework also exports a lot of useful voltage/current/opmode data to + userspace via sysfs. This could be used to help monitor device power + consumption and status. + + See Documentation/ABI/testing/sysfs-class-regulator diff --git a/kernel/Documentation/power/regulator/regulator.txt b/kernel/Documentation/power/regulator/regulator.txt new file mode 100644 index 000000000..b17e5833c --- /dev/null +++ b/kernel/Documentation/power/regulator/regulator.txt @@ -0,0 +1,30 @@ +Regulator Driver Interface +========================== + +The regulator driver interface is relatively simple and designed to allow +regulator drivers to register their services with the core framework. + + +Registration +============ + +Drivers can register a regulator by calling :- + +struct regulator_dev *regulator_register(struct regulator_desc *regulator_desc, + const struct regulator_config *config); + +This will register the regulator's capabilities and operations to the regulator +core. + +Regulators can be unregistered by calling :- + +void regulator_unregister(struct regulator_dev *rdev); + + +Regulator Events +================ +Regulators can send events (e.g. overtemperature, undervoltage, etc) to +consumer drivers by calling :- + +int regulator_notifier_call_chain(struct regulator_dev *rdev, + unsigned long event, void *data); |