1=================================== 2Regulator Consumer Driver Interface 3=================================== 4 5This text describes the regulator interface for consumer device drivers. 6Please see overview.txt for a description of the terms used in this text. 7 8 91. Consumer Regulator Access (static & dynamic drivers) 10======================================================= 11 12A consumer driver can get access to its supply regulator by calling :: 13 14 regulator = regulator_get(dev, "Vcc"); 15 16The consumer passes in its struct device pointer and power supply ID. The core 17then finds the correct regulator by consulting a machine specific lookup table. 18If the lookup is successful then this call will return a pointer to the struct 19regulator that supplies this consumer. 20 21To release the regulator the consumer driver should call :: 22 23 regulator_put(regulator); 24 25Consumers can be supplied by more than one regulator e.g. codec consumer with 26analog and digital supplies :: 27 28 digital = regulator_get(dev, "Vcc"); /* digital core */ 29 analog = regulator_get(dev, "Avdd"); /* analog */ 30 31The regulator access functions regulator_get() and regulator_put() will 32usually be called in your device drivers probe() and remove() respectively. 33 34 352. Regulator Output Enable & Disable (static & dynamic drivers) 36=============================================================== 37 38 39A consumer can enable its power supply by calling:: 40 41 int regulator_enable(regulator); 42 43NOTE: 44 The supply may already be enabled before regulator_enabled() is called. 45 This may happen if the consumer shares the regulator or the regulator has been 46 previously enabled by bootloader or kernel board initialization code. 47 48A consumer can determine if a regulator is enabled by calling:: 49 50 int regulator_is_enabled(regulator); 51 52This will return > zero when the regulator is enabled. 53 54 55A consumer can disable its supply when no longer needed by calling:: 56 57 int regulator_disable(regulator); 58 59NOTE: 60 This may not disable the supply if it's shared with other consumers. The 61 regulator will only be disabled when the enabled reference count is zero. 62 63Finally, a regulator can be forcefully disabled in the case of an emergency:: 64 65 int regulator_force_disable(regulator); 66 67NOTE: 68 this will immediately and forcefully shutdown the regulator output. All 69 consumers will be powered off. 70 71 723. Regulator Voltage Control & Status (dynamic drivers) 73======================================================= 74 75Some consumer drivers need to be able to dynamically change their supply 76voltage to match system operating points. e.g. CPUfreq drivers can scale 77voltage along with frequency to save power, SD drivers may need to select the 78correct card voltage, etc. 79 80Consumers can control their supply voltage by calling:: 81 82 int regulator_set_voltage(regulator, min_uV, max_uV); 83 84Where min_uV and max_uV are the minimum and maximum acceptable voltages in 85microvolts. 86 87NOTE: this can be called when the regulator is enabled or disabled. If called 88when enabled, then the voltage changes instantly, otherwise the voltage 89configuration changes and the voltage is physically set when the regulator is 90next enabled. 91 92The regulators configured voltage output can be found by calling:: 93 94 int regulator_get_voltage(regulator); 95 96NOTE: 97 get_voltage() will return the configured output voltage whether the 98 regulator is enabled or disabled and should NOT be used to determine regulator 99 output state. However this can be used in conjunction with is_enabled() to 100 determine the regulator physical output voltage. 101 102 1034. Regulator Current Limit Control & Status (dynamic drivers) 104============================================================= 105 106Some consumer drivers need to be able to dynamically change their supply 107current limit to match system operating points. e.g. LCD backlight driver can 108change the current limit to vary the backlight brightness, USB drivers may want 109to set the limit to 500mA when supplying power. 110 111Consumers can control their supply current limit by calling:: 112 113 int regulator_set_current_limit(regulator, min_uA, max_uA); 114 115Where min_uA and max_uA are the minimum and maximum acceptable current limit in 116microamps. 117 118NOTE: 119 this can be called when the regulator is enabled or disabled. If called 120 when enabled, then the current limit changes instantly, otherwise the current 121 limit configuration changes and the current limit is physically set when the 122 regulator is next enabled. 123 124A regulators current limit can be found by calling:: 125 126 int regulator_get_current_limit(regulator); 127 128NOTE: 129 get_current_limit() will return the current limit whether the regulator 130 is enabled or disabled and should not be used to determine regulator current 131 load. 132 133 1345. Regulator Operating Mode Control & Status (dynamic drivers) 135============================================================== 136 137Some consumers can further save system power by changing the operating mode of 138their supply regulator to be more efficient when the consumers operating state 139changes. e.g. consumer driver is idle and subsequently draws less current 140 141Regulator operating mode can be changed indirectly or directly. 142 143Indirect operating mode control. 144-------------------------------- 145Consumer drivers can request a change in their supply regulator operating mode 146by calling:: 147 148 int regulator_set_load(struct regulator *regulator, int load_uA); 149 150This will cause the core to recalculate the total load on the regulator (based 151on all its consumers) and change operating mode (if necessary and permitted) 152to best match the current operating load. 153 154The load_uA value can be determined from the consumer's datasheet. e.g. most 155datasheets have tables showing the maximum current consumed in certain 156situations. 157 158Most consumers will use indirect operating mode control since they have no 159knowledge of the regulator or whether the regulator is shared with other 160consumers. 161 162Direct operating mode control. 163------------------------------ 164 165Bespoke or tightly coupled drivers may want to directly control regulator 166operating mode depending on their operating point. This can be achieved by 167calling:: 168 169 int regulator_set_mode(struct regulator *regulator, unsigned int mode); 170 unsigned int regulator_get_mode(struct regulator *regulator); 171 172Direct mode will only be used by consumers that *know* about the regulator and 173are not sharing the regulator with other consumers. 174 175 1766. Regulator Events 177=================== 178 179Regulators can notify consumers of external events. Events could be received by 180consumers under regulator stress or failure conditions. 181 182Consumers can register interest in regulator events by calling:: 183 184 int regulator_register_notifier(struct regulator *regulator, 185 struct notifier_block *nb); 186 187Consumers can unregister interest by calling:: 188 189 int regulator_unregister_notifier(struct regulator *regulator, 190 struct notifier_block *nb); 191 192Regulators use the kernel notifier framework to send event to their interested 193consumers. 194 1957. Regulator Direct Register Access 196=================================== 197 198Some kinds of power management hardware or firmware are designed such that 199they need to do low-level hardware access to regulators, with no involvement 200from the kernel. Examples of such devices are: 201 202- clocksource with a voltage-controlled oscillator and control logic to change 203 the supply voltage over I2C to achieve a desired output clock rate 204- thermal management firmware that can issue an arbitrary I2C transaction to 205 perform system poweroff during overtemperature conditions 206 207To set up such a device/firmware, various parameters like I2C address of the 208regulator, addresses of various regulator registers etc. need to be configured 209to it. The regulator framework provides the following helpers for querying 210these details. 211 212Bus-specific details, like I2C addresses or transfer rates are handled by the 213regmap framework. To get the regulator's regmap (if supported), use:: 214 215 struct regmap *regulator_get_regmap(struct regulator *regulator); 216 217To obtain the hardware register offset and bitmask for the regulator's voltage 218selector register, use:: 219 220 int regulator_get_hardware_vsel_register(struct regulator *regulator, 221 unsigned *vsel_reg, 222 unsigned *vsel_mask); 223 224To convert a regulator framework voltage selector code (used by 225regulator_list_voltage) to a hardware-specific voltage selector that can be 226directly written to the voltage selector register, use:: 227 228 int regulator_list_hardware_vsel(struct regulator *regulator, 229 unsigned selector); 230