1 // SPDX-License-Identifier: GPL-2.0-only 2 /* 3 * Driver for Linear Technology LTC4215 I2C Hot Swap Controller 4 * 5 * Copyright (C) 2009 Ira W. Snyder <iws@ovro.caltech.edu> 6 * 7 * Datasheet: 8 * http://www.linear.com/pc/downloadDocument.do?navId=H0,C1,C1003,C1006,C1163,P17572,D12697 9 */ 10 11 #include <linux/kernel.h> 12 #include <linux/module.h> 13 #include <linux/init.h> 14 #include <linux/err.h> 15 #include <linux/slab.h> 16 #include <linux/i2c.h> 17 #include <linux/hwmon.h> 18 #include <linux/hwmon-sysfs.h> 19 #include <linux/jiffies.h> 20 21 /* Here are names of the chip's registers (a.k.a. commands) */ 22 enum ltc4215_cmd { 23 LTC4215_CONTROL = 0x00, /* rw */ 24 LTC4215_ALERT = 0x01, /* rw */ 25 LTC4215_STATUS = 0x02, /* ro */ 26 LTC4215_FAULT = 0x03, /* rw */ 27 LTC4215_SENSE = 0x04, /* rw */ 28 LTC4215_SOURCE = 0x05, /* rw */ 29 LTC4215_ADIN = 0x06, /* rw */ 30 }; 31 32 struct ltc4215_data { 33 struct i2c_client *client; 34 35 struct mutex update_lock; 36 bool valid; 37 unsigned long last_updated; /* in jiffies */ 38 39 /* Registers */ 40 u8 regs[7]; 41 }; 42 43 static struct ltc4215_data *ltc4215_update_device(struct device *dev) 44 { 45 struct ltc4215_data *data = dev_get_drvdata(dev); 46 struct i2c_client *client = data->client; 47 s32 val; 48 int i; 49 50 mutex_lock(&data->update_lock); 51 52 /* The chip's A/D updates 10 times per second */ 53 if (time_after(jiffies, data->last_updated + HZ / 10) || !data->valid) { 54 55 dev_dbg(&client->dev, "Starting ltc4215 update\n"); 56 57 /* Read all registers */ 58 for (i = 0; i < ARRAY_SIZE(data->regs); i++) { 59 val = i2c_smbus_read_byte_data(client, i); 60 if (unlikely(val < 0)) 61 data->regs[i] = 0; 62 else 63 data->regs[i] = val; 64 } 65 66 data->last_updated = jiffies; 67 data->valid = true; 68 } 69 70 mutex_unlock(&data->update_lock); 71 72 return data; 73 } 74 75 /* Return the voltage from the given register in millivolts */ 76 static int ltc4215_get_voltage(struct device *dev, u8 reg) 77 { 78 struct ltc4215_data *data = ltc4215_update_device(dev); 79 const u8 regval = data->regs[reg]; 80 u32 voltage = 0; 81 82 switch (reg) { 83 case LTC4215_SENSE: 84 /* 151 uV per increment */ 85 voltage = regval * 151 / 1000; 86 break; 87 case LTC4215_SOURCE: 88 /* 60.5 mV per increment */ 89 voltage = regval * 605 / 10; 90 break; 91 case LTC4215_ADIN: 92 /* 93 * The ADIN input is divided by 12.5, and has 4.82 mV 94 * per increment, so we have the additional multiply 95 */ 96 voltage = regval * 482 * 125 / 1000; 97 break; 98 default: 99 /* If we get here, the developer messed up */ 100 WARN_ON_ONCE(1); 101 break; 102 } 103 104 return voltage; 105 } 106 107 /* Return the current from the sense resistor in mA */ 108 static unsigned int ltc4215_get_current(struct device *dev) 109 { 110 struct ltc4215_data *data = ltc4215_update_device(dev); 111 112 /* 113 * The strange looking conversions that follow are fixed-point 114 * math, since we cannot do floating point in the kernel. 115 * 116 * Step 1: convert sense register to microVolts 117 * Step 2: convert voltage to milliAmperes 118 * 119 * If you play around with the V=IR equation, you come up with 120 * the following: X uV / Y mOhm == Z mA 121 * 122 * With the resistors that are fractions of a milliOhm, we multiply 123 * the voltage and resistance by 10, to shift the decimal point. 124 * Now we can use the normal division operator again. 125 */ 126 127 /* Calculate voltage in microVolts (151 uV per increment) */ 128 const unsigned int voltage = data->regs[LTC4215_SENSE] * 151; 129 130 /* Calculate current in milliAmperes (4 milliOhm sense resistor) */ 131 const unsigned int curr = voltage / 4; 132 133 return curr; 134 } 135 136 static ssize_t ltc4215_voltage_show(struct device *dev, 137 struct device_attribute *da, char *buf) 138 { 139 struct sensor_device_attribute *attr = to_sensor_dev_attr(da); 140 const int voltage = ltc4215_get_voltage(dev, attr->index); 141 142 return sysfs_emit(buf, "%d\n", voltage); 143 } 144 145 static ssize_t ltc4215_current_show(struct device *dev, 146 struct device_attribute *da, char *buf) 147 { 148 const unsigned int curr = ltc4215_get_current(dev); 149 150 return sysfs_emit(buf, "%u\n", curr); 151 } 152 153 static ssize_t ltc4215_power_show(struct device *dev, 154 struct device_attribute *da, char *buf) 155 { 156 const unsigned int curr = ltc4215_get_current(dev); 157 const int output_voltage = ltc4215_get_voltage(dev, LTC4215_ADIN); 158 159 /* current in mA * voltage in mV == power in uW */ 160 const unsigned int power = abs(output_voltage * curr); 161 162 return sysfs_emit(buf, "%u\n", power); 163 } 164 165 static ssize_t ltc4215_alarm_show(struct device *dev, 166 struct device_attribute *da, char *buf) 167 { 168 struct sensor_device_attribute *attr = to_sensor_dev_attr(da); 169 struct ltc4215_data *data = ltc4215_update_device(dev); 170 const u8 reg = data->regs[LTC4215_STATUS]; 171 const u32 mask = attr->index; 172 173 return sysfs_emit(buf, "%u\n", !!(reg & mask)); 174 } 175 176 /* 177 * These macros are used below in constructing device attribute objects 178 * for use with sysfs_create_group() to make a sysfs device file 179 * for each register. 180 */ 181 182 /* Construct a sensor_device_attribute structure for each register */ 183 184 /* Current */ 185 static SENSOR_DEVICE_ATTR_RO(curr1_input, ltc4215_current, 0); 186 static SENSOR_DEVICE_ATTR_RO(curr1_max_alarm, ltc4215_alarm, 1 << 2); 187 188 /* Power (virtual) */ 189 static SENSOR_DEVICE_ATTR_RO(power1_input, ltc4215_power, 0); 190 191 /* Input Voltage */ 192 static SENSOR_DEVICE_ATTR_RO(in1_input, ltc4215_voltage, LTC4215_ADIN); 193 static SENSOR_DEVICE_ATTR_RO(in1_max_alarm, ltc4215_alarm, 1 << 0); 194 static SENSOR_DEVICE_ATTR_RO(in1_min_alarm, ltc4215_alarm, 1 << 1); 195 196 /* Output Voltage */ 197 static SENSOR_DEVICE_ATTR_RO(in2_input, ltc4215_voltage, LTC4215_SOURCE); 198 static SENSOR_DEVICE_ATTR_RO(in2_min_alarm, ltc4215_alarm, 1 << 3); 199 200 /* 201 * Finally, construct an array of pointers to members of the above objects, 202 * as required for sysfs_create_group() 203 */ 204 static struct attribute *ltc4215_attrs[] = { 205 &sensor_dev_attr_curr1_input.dev_attr.attr, 206 &sensor_dev_attr_curr1_max_alarm.dev_attr.attr, 207 208 &sensor_dev_attr_power1_input.dev_attr.attr, 209 210 &sensor_dev_attr_in1_input.dev_attr.attr, 211 &sensor_dev_attr_in1_max_alarm.dev_attr.attr, 212 &sensor_dev_attr_in1_min_alarm.dev_attr.attr, 213 214 &sensor_dev_attr_in2_input.dev_attr.attr, 215 &sensor_dev_attr_in2_min_alarm.dev_attr.attr, 216 217 NULL, 218 }; 219 ATTRIBUTE_GROUPS(ltc4215); 220 221 static int ltc4215_probe(struct i2c_client *client) 222 { 223 struct i2c_adapter *adapter = client->adapter; 224 struct device *dev = &client->dev; 225 struct ltc4215_data *data; 226 struct device *hwmon_dev; 227 228 if (!i2c_check_functionality(adapter, I2C_FUNC_SMBUS_BYTE_DATA)) 229 return -ENODEV; 230 231 data = devm_kzalloc(dev, sizeof(*data), GFP_KERNEL); 232 if (!data) 233 return -ENOMEM; 234 235 data->client = client; 236 mutex_init(&data->update_lock); 237 238 /* Initialize the LTC4215 chip */ 239 i2c_smbus_write_byte_data(client, LTC4215_FAULT, 0x00); 240 241 hwmon_dev = devm_hwmon_device_register_with_groups(dev, client->name, 242 data, 243 ltc4215_groups); 244 return PTR_ERR_OR_ZERO(hwmon_dev); 245 } 246 247 static const struct i2c_device_id ltc4215_id[] = { 248 { "ltc4215", 0 }, 249 { } 250 }; 251 MODULE_DEVICE_TABLE(i2c, ltc4215_id); 252 253 /* This is the driver that will be inserted */ 254 static struct i2c_driver ltc4215_driver = { 255 .driver = { 256 .name = "ltc4215", 257 }, 258 .probe = ltc4215_probe, 259 .id_table = ltc4215_id, 260 }; 261 262 module_i2c_driver(ltc4215_driver); 263 264 MODULE_AUTHOR("Ira W. Snyder <iws@ovro.caltech.edu>"); 265 MODULE_DESCRIPTION("LTC4215 driver"); 266 MODULE_LICENSE("GPL"); 267