| 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. |
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| |
| 1. Consumer Regulator Access (static & dynamic drivers) |
| ======================================================= |
| |
| A consumer driver can get access to it's supply regulator by calling :- |
| |
| regulator = regulator_get(dev, "Vcc"); |
| |
| The consumer passes in it's 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 :- |
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| 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 it's 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 :- |
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| int regulator_is_enabled(regulator); |
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| This will return > zero when the regulator is enabled. |
| |
| |
| A consumer can disable it's supply when no longer needed by calling :- |
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| int regulator_disable(regulator); |
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| 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 :- |
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| int regulator_force_disable(regulator); |
| |
| NOTE: this will immediately and forcefully shutdown the regulator output. All |
| consumers will be powered off. |
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| |
| 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_optimum_mode(struct regulator *regulator, int load_uA); |
| |
| This will cause the core to recalculate the total load on the regulator (based |
| on all it's 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 consumers datasheet. e.g.most |
| datasheets have tables showing the max 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 uregister 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. |