Based on kernel version 3.19. Page generated on 2015-02-13 21:22 EST.
1 Regulator Consumer Driver Interface 2 =================================== 3 4 This text describes the regulator interface for consumer device drivers. 5 Please see overview.txt for a description of the terms used in this text. 6 7 8 1. Consumer Regulator Access (static & dynamic drivers) 9 ======================================================= 10 11 A consumer driver can get access to its supply regulator by calling :- 12 13 regulator = regulator_get(dev, "Vcc"); 14 15 The consumer passes in its struct device pointer and power supply ID. The core 16 then finds the correct regulator by consulting a machine specific lookup table. 17 If the lookup is successful then this call will return a pointer to the struct 18 regulator that supplies this consumer. 19 20 To release the regulator the consumer driver should call :- 21 22 regulator_put(regulator); 23 24 Consumers can be supplied by more than one regulator e.g. codec consumer with 25 analog and digital supplies :- 26 27 digital = regulator_get(dev, "Vcc"); /* digital core */ 28 analog = regulator_get(dev, "Avdd"); /* analog */ 29 30 The regulator access functions regulator_get() and regulator_put() will 31 usually be called in your device drivers probe() and remove() respectively. 32 33 34 2. Regulator Output Enable & Disable (static & dynamic drivers) 35 ==================================================================== 36 37 A consumer can enable its power supply by calling:- 38 39 int regulator_enable(regulator); 40 41 NOTE: The supply may already be enabled before regulator_enabled() is called. 42 This may happen if the consumer shares the regulator or the regulator has been 43 previously enabled by bootloader or kernel board initialization code. 44 45 A consumer can determine if a regulator is enabled by calling :- 46 47 int regulator_is_enabled(regulator); 48 49 This will return > zero when the regulator is enabled. 50 51 52 A consumer can disable its supply when no longer needed by calling :- 53 54 int regulator_disable(regulator); 55 56 NOTE: This may not disable the supply if it's shared with other consumers. The 57 regulator will only be disabled when the enabled reference count is zero. 58 59 Finally, a regulator can be forcefully disabled in the case of an emergency :- 60 61 int regulator_force_disable(regulator); 62 63 NOTE: this will immediately and forcefully shutdown the regulator output. All 64 consumers will be powered off. 65 66 67 3. Regulator Voltage Control & Status (dynamic drivers) 68 ====================================================== 69 70 Some consumer drivers need to be able to dynamically change their supply 71 voltage to match system operating points. e.g. CPUfreq drivers can scale 72 voltage along with frequency to save power, SD drivers may need to select the 73 correct card voltage, etc. 74 75 Consumers can control their supply voltage by calling :- 76 77 int regulator_set_voltage(regulator, min_uV, max_uV); 78 79 Where min_uV and max_uV are the minimum and maximum acceptable voltages in 80 microvolts. 81 82 NOTE: this can be called when the regulator is enabled or disabled. If called 83 when enabled, then the voltage changes instantly, otherwise the voltage 84 configuration changes and the voltage is physically set when the regulator is 85 next enabled. 86 87 The regulators configured voltage output can be found by calling :- 88 89 int regulator_get_voltage(regulator); 90 91 NOTE: get_voltage() will return the configured output voltage whether the 92 regulator is enabled or disabled and should NOT be used to determine regulator 93 output state. However this can be used in conjunction with is_enabled() to 94 determine the regulator physical output voltage. 95 96 97 4. Regulator Current Limit Control & Status (dynamic drivers) 98 =========================================================== 99 100 Some consumer drivers need to be able to dynamically change their supply 101 current limit to match system operating points. e.g. LCD backlight driver can 102 change the current limit to vary the backlight brightness, USB drivers may want 103 to set the limit to 500mA when supplying power. 104 105 Consumers can control their supply current limit by calling :- 106 107 int regulator_set_current_limit(regulator, min_uA, max_uA); 108 109 Where min_uA and max_uA are the minimum and maximum acceptable current limit in 110 microamps. 111 112 NOTE: this can be called when the regulator is enabled or disabled. If called 113 when enabled, then the current limit changes instantly, otherwise the current 114 limit configuration changes and the current limit is physically set when the 115 regulator is next enabled. 116 117 A regulators current limit can be found by calling :- 118 119 int regulator_get_current_limit(regulator); 120 121 NOTE: get_current_limit() will return the current limit whether the regulator 122 is enabled or disabled and should not be used to determine regulator current 123 load. 124 125 126 5. Regulator Operating Mode Control & Status (dynamic drivers) 127 ============================================================= 128 129 Some consumers can further save system power by changing the operating mode of 130 their supply regulator to be more efficient when the consumers operating state 131 changes. e.g. consumer driver is idle and subsequently draws less current 132 133 Regulator operating mode can be changed indirectly or directly. 134 135 Indirect operating mode control. 136 -------------------------------- 137 Consumer drivers can request a change in their supply regulator operating mode 138 by calling :- 139 140 int regulator_set_optimum_mode(struct regulator *regulator, int load_uA); 141 142 This will cause the core to recalculate the total load on the regulator (based 143 on all its consumers) and change operating mode (if necessary and permitted) 144 to best match the current operating load. 145 146 The load_uA value can be determined from the consumer's datasheet. e.g. most 147 datasheets have tables showing the maximum current consumed in certain 148 situations. 149 150 Most consumers will use indirect operating mode control since they have no 151 knowledge of the regulator or whether the regulator is shared with other 152 consumers. 153 154 Direct operating mode control. 155 ------------------------------ 156 Bespoke or tightly coupled drivers may want to directly control regulator 157 operating mode depending on their operating point. This can be achieved by 158 calling :- 159 160 int regulator_set_mode(struct regulator *regulator, unsigned int mode); 161 unsigned int regulator_get_mode(struct regulator *regulator); 162 163 Direct mode will only be used by consumers that *know* about the regulator and 164 are not sharing the regulator with other consumers. 165 166 167 6. Regulator Events 168 =================== 169 Regulators can notify consumers of external events. Events could be received by 170 consumers under regulator stress or failure conditions. 171 172 Consumers can register interest in regulator events by calling :- 173 174 int regulator_register_notifier(struct regulator *regulator, 175 struct notifier_block *nb); 176 177 Consumers can unregister interest by calling :- 178 179 int regulator_unregister_notifier(struct regulator *regulator, 180 struct notifier_block *nb); 181 182 Regulators use the kernel notifier framework to send event to their interested 183 consumers. 184 185 7. Regulator Direct Register Access 186 =================================== 187 Some kinds of power management hardware or firmware are designed such that 188 they need to do low-level hardware access to regulators, with no involvement 189 from the kernel. Examples of such devices are: 190 191 - clocksource with a voltage-controlled oscillator and control logic to change 192 the supply voltage over I2C to achieve a desired output clock rate 193 - thermal management firmware that can issue an arbitrary I2C transaction to 194 perform system poweroff during overtemperature conditions 195 196 To set up such a device/firmware, various parameters like I2C address of the 197 regulator, addresses of various regulator registers etc. need to be configured 198 to it. The regulator framework provides the following helpers for querying 199 these details. 200 201 Bus-specific details, like I2C addresses or transfer rates are handled by the 202 regmap framework. To get the regulator's regmap (if supported), use :- 203 204 struct regmap *regulator_get_regmap(struct regulator *regulator); 205 206 To obtain the hardware register offset and bitmask for the regulator's voltage 207 selector register, use :- 208 209 int regulator_get_hardware_vsel_register(struct regulator *regulator, 210 unsigned *vsel_reg, 211 unsigned *vsel_mask); 212 213 To convert a regulator framework voltage selector code (used by 214 regulator_list_voltage) to a hardware-specific voltage selector that can be 215 directly written to the voltage selector register, use :- 216 217 int regulator_list_hardware_vsel(struct regulator *regulator, 218 unsigned selector);