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1// SPDX-License-Identifier: GPL-2.0-only2/*3 * Driver for Linear Technology LTC4215 I2C Hot Swap Controller4 *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,D126979 */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) */22enum 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 32struct 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 43static 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 else63 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 */76static 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 mV94 * per increment, so we have the additional multiply95 */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 */108static 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-point114 * math, since we cannot do floating point in the kernel.115 *116 * Step 1: convert sense register to microVolts117 * Step 2: convert voltage to milliAmperes118 *119 * If you play around with the V=IR equation, you come up with120 * the following: X uV / Y mOhm == Z mA121 *122 * With the resistors that are fractions of a milliOhm, we multiply123 * 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 136static 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 145static 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 153static 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 165static 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 objects178 * for use with sysfs_create_group() to make a sysfs device file179 * for each register.180 */181 182/* Construct a sensor_device_attribute structure for each register */183 184/* Current */185static SENSOR_DEVICE_ATTR_RO(curr1_input, ltc4215_current, 0);186static SENSOR_DEVICE_ATTR_RO(curr1_max_alarm, ltc4215_alarm, 1 << 2);187 188/* Power (virtual) */189static SENSOR_DEVICE_ATTR_RO(power1_input, ltc4215_power, 0);190 191/* Input Voltage */192static SENSOR_DEVICE_ATTR_RO(in1_input, ltc4215_voltage, LTC4215_ADIN);193static SENSOR_DEVICE_ATTR_RO(in1_max_alarm, ltc4215_alarm, 1 << 0);194static SENSOR_DEVICE_ATTR_RO(in1_min_alarm, ltc4215_alarm, 1 << 1);195 196/* Output Voltage */197static SENSOR_DEVICE_ATTR_RO(in2_input, ltc4215_voltage, LTC4215_SOURCE);198static 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 */204static 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};219ATTRIBUTE_GROUPS(ltc4215);220 221static 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 247static const struct i2c_device_id ltc4215_id[] = {248 { "ltc4215" },249 { }250};251MODULE_DEVICE_TABLE(i2c, ltc4215_id);252 253/* This is the driver that will be inserted */254static struct i2c_driver ltc4215_driver = {255 .driver = {256 .name = "ltc4215",257 },258 .probe = ltc4215_probe,259 .id_table = ltc4215_id,260};261 262module_i2c_driver(ltc4215_driver);263 264MODULE_AUTHOR("Ira W. Snyder <iws@ovro.caltech.edu>");265MODULE_DESCRIPTION("LTC4215 driver");266MODULE_LICENSE("GPL");267