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authorDaniel Baumann <daniel.baumann@progress-linux.org>2024-04-27 10:05:51 +0000
committerDaniel Baumann <daniel.baumann@progress-linux.org>2024-04-27 10:05:51 +0000
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treea94efe259b9009378be6d90eb30d2b019d95c194 /Documentation/power/regulator
parentInitial commit. (diff)
downloadlinux-upstream/5.10.209.tar.xz
linux-upstream/5.10.209.zip
Adding upstream version 5.10.209.upstream/5.10.209upstream
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
Diffstat (limited to '')
-rw-r--r--Documentation/power/regulator/consumer.rst229
-rw-r--r--Documentation/power/regulator/design.rst38
-rw-r--r--Documentation/power/regulator/machine.rst97
-rw-r--r--Documentation/power/regulator/overview.rst178
-rw-r--r--Documentation/power/regulator/regulator.rst32
5 files changed, 574 insertions, 0 deletions
diff --git a/Documentation/power/regulator/consumer.rst b/Documentation/power/regulator/consumer.rst
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+===================================
+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/Documentation/power/regulator/design.rst b/Documentation/power/regulator/design.rst
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+++ b/Documentation/power/regulator/design.rst
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+==========================
+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.
+
+.. note::
+
+ 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.
+
+.. note::
+
+ 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/Documentation/power/regulator/machine.rst b/Documentation/power/regulator/machine.rst
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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.
+
+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[] = {
+ REGULATOR_SUPPLY("Vcc", "consumer B"),
+ };
+
+ static struct regulator_consumer_supply regulator2_consumers[] = {
+ REGULATOR_SUPPLY("Vcc", "consumer A"),
+ };
+
+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 = &regulator1_data,
+ },
+ },
+ {
+ .name = "regulator",
+ .id = DCDC_2,
+ .dev = {
+ .platform_data = &regulator2_data,
+ },
+ },
+ };
+ /* register regulator 1 device */
+ platform_device_register(&regulator_devices[0]);
+
+ /* register regulator 2 device */
+ platform_device_register(&regulator_devices[1]);
diff --git a/Documentation/power/regulator/overview.rst b/Documentation/power/regulator/overview.rst
new file mode 100644
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+++ b/Documentation/power/regulator/overview.rst
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+=============================================
+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:
+
+ - Regulator
+ - Electronic device that supplies power to other devices.
+ Most regulators can enable and disable their output while
+ some can control their output voltage and or current.
+
+ Input Voltage -> Regulator -> Output Voltage
+
+
+ - PMIC
+ - Power Management IC. An IC that contains numerous
+ regulators and often contains other subsystems.
+
+
+ - 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.
+
+
+ - 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
+
+
+ - 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.rst
+
+ 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.rst
+
+ 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.rst
+
+ 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/Documentation/power/regulator/regulator.rst b/Documentation/power/regulator/regulator.rst
new file mode 100644
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+==========================
+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);