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, command: 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(lock: &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, reg: attr->index); |
141 | |
142 | return sysfs_emit(buf, fmt: "%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, fmt: "%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, reg: 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, fmt: "%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, fmt: "%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(adap: adapter, I2C_FUNC_SMBUS_BYTE_DATA)) |
229 | return -ENODEV; |
230 | |
231 | data = devm_kzalloc(dev, size: 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, command: LTC4215_FAULT, value: 0x00); |
240 | |
241 | hwmon_dev = devm_hwmon_device_register_with_groups(dev, name: client->name, |
242 | drvdata: data, |
243 | groups: ltc4215_groups); |
244 | return PTR_ERR_OR_ZERO(ptr: 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 | |