1 =================================== 2 Regulator Consumer Driver Interface 3 =================================== 4 5 This text describes the regulator interface for consumer device drivers. 6 Please see overview.txt for a description of the terms used in this text. 7 8 9 1. Consumer Regulator Access (static & dynamic drivers) 10 ======================================================= 11 12 A consumer driver can get access to its supply regulator by calling :: 13 14 regulator = regulator_get(dev, "Vcc"); 15 16 The consumer passes in its struct device pointer and power supply ID. The core 17 then finds the correct regulator by consulting a machine specific lookup table. 18 If the lookup is successful then this call will return a pointer to the struct 19 regulator that supplies this consumer. 20 21 To release the regulator the consumer driver should call :: 22 23 regulator_put(regulator); 24 25 Consumers can be supplied by more than one regulator e.g. codec consumer with 26 analog and digital supplies :: 27 28 digital = regulator_get(dev, "Vcc"); /* digital core */ 29 analog = regulator_get(dev, "Avdd"); /* analog */ 30 31 The regulator access functions regulator_get() and regulator_put() will 32 usually be called in your device drivers probe() and remove() respectively. 33 34 35 2. Regulator Output Enable & Disable (static & dynamic drivers) 36 =============================================================== 37 38 39 A consumer can enable its power supply by calling:: 40 41 int regulator_enable(regulator); 42 43 NOTE: 44 The supply may already be enabled before regulator_enable() 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 48 A consumer can determine if a regulator is enabled by calling:: 49 50 int regulator_is_enabled(regulator); 51 52 This will return > zero when the regulator is enabled. 53 54 55 A consumer can disable its supply when no longer needed by calling:: 56 57 int regulator_disable(regulator); 58 59 NOTE: 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 63 Finally, a regulator can be forcefully disabled in the case of an emergency:: 64 65 int regulator_force_disable(regulator); 66 67 NOTE: 68 this will immediately and forcefully shutdown the regulator output. All 69 consumers will be powered off. 70 71 72 3. Regulator Voltage Control & Status (dynamic drivers) 73 ======================================================= 74 75 Some consumer drivers need to be able to dynamically change their supply 76 voltage to match system operating points. e.g. CPUfreq drivers can scale 77 voltage along with frequency to save power, SD drivers may need to select the 78 correct card voltage, etc. 79 80 Consumers can control their supply voltage by calling:: 81 82 int regulator_set_voltage(regulator, min_uV, max_uV); 83 84 Where min_uV and max_uV are the minimum and maximum acceptable voltages in 85 microvolts. 86 87 NOTE: this can be called when the regulator is enabled or disabled. If called 88 when enabled, then the voltage changes instantly, otherwise the voltage 89 configuration changes and the voltage is physically set when the regulator is 90 next enabled. 91 92 The regulators configured voltage output can be found by calling:: 93 94 int regulator_get_voltage(regulator); 95 96 NOTE: 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. 101 102 103 4. Regulator Current Limit Control & Status (dynamic drivers) 104 ============================================================= 105 106 Some consumer drivers need to be able to dynamically change their supply 107 current limit to match system operating points. e.g. LCD backlight driver can 108 change the current limit to vary the backlight brightness, USB drivers may want 109 to set the limit to 500mA when supplying power. 110 111 Consumers can control their supply current limit by calling:: 112 113 int regulator_set_current_limit(regulator, min_uA, max_uA); 114 115 Where min_uA and max_uA are the minimum and maximum acceptable current limit in 116 microamps. 117 118 NOTE: 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. 123 124 A regulators current limit can be found by calling:: 125 126 int regulator_get_current_limit(regulator); 127 128 NOTE: 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. 132 133 134 5. Regulator Operating Mode Control & Status (dynamic drivers) 135 ============================================================== 136 137 Some consumers can further save system power by changing the operating mode of 138 their supply regulator to be more efficient when the consumers operating state 139 changes. e.g. consumer driver is idle and subsequently draws less current 140 141 Regulator operating mode can be changed indirectly or directly. 142 143 Indirect operating mode control. 144 -------------------------------- 145 Consumer drivers can request a change in their supply regulator operating mode 146 by calling:: 147 148 int regulator_set_load(struct regulator *regulator, int load_uA); 149 150 This will cause the core to recalculate the total load on the regulator (based 151 on all its consumers) and change operating mode (if necessary and permitted) 152 to best match the current operating load. 153 154 The load_uA value can be determined from the consumer's datasheet. e.g. most 155 datasheets have tables showing the maximum current consumed in certain 156 situations. 157 158 Most consumers will use indirect operating mode control since they have no 159 knowledge of the regulator or whether the regulator is shared with other 160 consumers. 161 162 Direct operating mode control. 163 ------------------------------ 164 165 Bespoke or tightly coupled drivers may want to directly control regulator 166 operating mode depending on their operating point. This can be achieved by 167 calling:: 168 169 int regulator_set_mode(struct regulator *regulator, unsigned int mode); 170 unsigned int regulator_get_mode(struct regulator *regulator); 171 172 Direct mode will only be used by consumers that *know* about the regulator and 173 are not sharing the regulator with other consumers. 174 175 176 6. Regulator Events 177 =================== 178 179 Regulators can notify consumers of external events. Events could be received by 180 consumers under regulator stress or failure conditions. 181 182 Consumers can register interest in regulator events by calling:: 183 184 int regulator_register_notifier(struct regulator *regulator, 185 struct notifier_block *nb); 186 187 Consumers can unregister interest by calling:: 188 189 int regulator_unregister_notifier(struct regulator *regulator, 190 struct notifier_block *nb); 191 192 Regulators use the kernel notifier framework to send event to their interested 193 consumers. 194 195 7. Regulator Direct Register Access 196 =================================== 197 198 Some kinds of power management hardware or firmware are designed such that 199 they need to do low-level hardware access to regulators, with no involvement 200 from 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 206 207 To set up such a device/firmware, various parameters like I2C address of the 208 regulator, addresses of various regulator registers etc. need to be configured 209 to it. The regulator framework provides the following helpers for querying 210 these details. 211 212 Bus-specific details, like I2C addresses or transfer rates are handled by the 213 regmap framework. To get the regulator's regmap (if supported), use:: 214 215 struct regmap *regulator_get_regmap(struct regulator *regulator); 216 217 To obtain the hardware register offset and bitmask for the regulator's voltage 218 selector register, use:: 219 220 int regulator_get_hardware_vsel_register(struct regulator *regulator, 221 unsigned *vsel_reg, 222 unsigned *vsel_mask); 223 224 To convert a regulator framework voltage selector code (used by 225 regulator_list_voltage) to a hardware-specific voltage selector that can be 226 directly written to the voltage selector register, use:: 227 228 int regulator_list_hardware_vsel(struct regulator *regulator, 229 unsigned selector); 230 231 To access the hardware for enabling/disabling the regulator, consumers must 232 use regulator_get_exclusive(), as it can't work if there's more than one 233 consumer. To enable/disable regulator use:: 234 235 int regulator_hardware_enable(struct regulator *regulator, bool enable);
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