xref: /openbmc/linux/drivers/hwmon/max127.c (revision 2fa5ebe3) 
1 // SPDX-License-Identifier: GPL-2.0+
2 /*
3  * Hardware monitoring driver for MAX127.
4  *
5  * Copyright (c) 2020 Facebook Inc.
6  */
7 
8 #include <linux/err.h>
9 #include <linux/hwmon.h>
10 #include <linux/i2c.h>
11 #include <linux/init.h>
12 #include <linux/module.h>
13 
14 /*
15  * MAX127 Control Byte. Refer to MAX127 datasheet, Table 1 "Control-Byte
16  * Format" for details.
17  */
18 #define MAX127_CTRL_START	BIT(7)
19 #define MAX127_CTRL_SEL_SHIFT	4
20 #define MAX127_CTRL_RNG		BIT(3)
21 #define MAX127_CTRL_BIP		BIT(2)
22 #define MAX127_CTRL_PD1		BIT(1)
23 #define MAX127_CTRL_PD0		BIT(0)
24 
25 #define MAX127_NUM_CHANNELS	8
26 #define MAX127_SET_CHANNEL(ch)	(((ch) & 7) << MAX127_CTRL_SEL_SHIFT)
27 
28 /*
29  * MAX127 channel input ranges. Refer to MAX127 datasheet, Table 3 "Range
30  * and Polarity Selection" for details.
31  */
32 #define MAX127_FULL_RANGE	10000	/* 10V */
33 #define MAX127_HALF_RANGE	5000	/* 5V */
34 
35 /*
36  * MAX127 returns 2 bytes at read:
37  *   - the first byte contains data[11:4].
38  *   - the second byte contains data[3:0] (MSB) and 4 dummy 0s (LSB).
39  * Refer to MAX127 datasheet, "Read a Conversion (Read Cycle)" section
40  * for details.
41  */
42 #define MAX127_DATA_LEN		2
43 #define MAX127_DATA_SHIFT	4
44 
45 #define MAX127_SIGN_BIT		BIT(11)
46 
47 struct max127_data {
48 	struct mutex lock;
49 	struct i2c_client *client;
50 	u8 ctrl_byte[MAX127_NUM_CHANNELS];
51 };
52 
53 static int max127_select_channel(struct i2c_client *client, u8 ctrl_byte)
54 {
55 	int status;
56 	struct i2c_msg msg = {
57 		.addr = client->addr,
58 		.flags = 0,
59 		.len = sizeof(ctrl_byte),
60 		.buf = &ctrl_byte,
61 	};
62 
63 	status = i2c_transfer(client->adapter, &msg, 1);
64 	if (status < 0)
65 		return status;
66 	if (status != 1)
67 		return -EIO;
68 
69 	return 0;
70 }
71 
72 static int max127_read_channel(struct i2c_client *client, long *val)
73 {
74 	int status;
75 	u8 i2c_data[MAX127_DATA_LEN];
76 	struct i2c_msg msg = {
77 		.addr = client->addr,
78 		.flags = I2C_M_RD,
79 		.len = sizeof(i2c_data),
80 		.buf = i2c_data,
81 	};
82 
83 	status = i2c_transfer(client->adapter, &msg, 1);
84 	if (status < 0)
85 		return status;
86 	if (status != 1)
87 		return -EIO;
88 
89 	*val = (i2c_data[1] >> MAX127_DATA_SHIFT) |
90 		((u16)i2c_data[0] << MAX127_DATA_SHIFT);
91 	return 0;
92 }
93 
94 static long max127_process_raw(u8 ctrl_byte, long raw)
95 {
96 	long scale, weight;
97 
98 	/*
99 	 * MAX127's data coding is binary in unipolar mode with 1 LSB =
100 	 * (Full-Scale/4096) and two’s complement binary in bipolar mode
101 	 * with 1 LSB = [(2 x |FS|)/4096].
102 	 * Refer to MAX127 datasheet, "Transfer Function" section for
103 	 * details.
104 	 */
105 	scale = (ctrl_byte & MAX127_CTRL_RNG) ? MAX127_FULL_RANGE :
106 						MAX127_HALF_RANGE;
107 	if (ctrl_byte & MAX127_CTRL_BIP) {
108 		weight = (raw & MAX127_SIGN_BIT);
109 		raw &= ~MAX127_SIGN_BIT;
110 		raw -= weight;
111 		raw *= 2;
112 	}
113 
114 	return raw * scale / 4096;
115 }
116 
117 static int max127_read_input(struct max127_data *data, int channel, long *val)
118 {
119 	long raw;
120 	int status;
121 	struct i2c_client *client = data->client;
122 	u8 ctrl_byte = data->ctrl_byte[channel];
123 
124 	mutex_lock(&data->lock);
125 
126 	status = max127_select_channel(client, ctrl_byte);
127 	if (status)
128 		goto exit;
129 
130 	status = max127_read_channel(client, &raw);
131 	if (status)
132 		goto exit;
133 
134 	*val = max127_process_raw(ctrl_byte, raw);
135 
136 exit:
137 	mutex_unlock(&data->lock);
138 	return status;
139 }
140 
141 static int max127_read_min(struct max127_data *data, int channel, long *val)
142 {
143 	u8 rng_bip = (data->ctrl_byte[channel] >> 2) & 3;
144 	static const int min_input_map[4] = {
145 		0,			/* RNG=0, BIP=0 */
146 		-MAX127_HALF_RANGE,	/* RNG=0, BIP=1 */
147 		0,			/* RNG=1, BIP=0 */
148 		-MAX127_FULL_RANGE,	/* RNG=1, BIP=1 */
149 	};
150 
151 	*val = min_input_map[rng_bip];
152 	return 0;
153 }
154 
155 static int max127_read_max(struct max127_data *data, int channel, long *val)
156 {
157 	u8 rng_bip = (data->ctrl_byte[channel] >> 2) & 3;
158 	static const int max_input_map[4] = {
159 		MAX127_HALF_RANGE,	/* RNG=0, BIP=0 */
160 		MAX127_HALF_RANGE,	/* RNG=0, BIP=1 */
161 		MAX127_FULL_RANGE,	/* RNG=1, BIP=0 */
162 		MAX127_FULL_RANGE,	/* RNG=1, BIP=1 */
163 	};
164 
165 	*val = max_input_map[rng_bip];
166 	return 0;
167 }
168 
169 static int max127_write_min(struct max127_data *data, int channel, long val)
170 {
171 	u8 ctrl;
172 
173 	mutex_lock(&data->lock);
174 
175 	ctrl = data->ctrl_byte[channel];
176 	if (val <= -MAX127_FULL_RANGE) {
177 		ctrl |= (MAX127_CTRL_RNG | MAX127_CTRL_BIP);
178 	} else if (val < 0) {
179 		ctrl |= MAX127_CTRL_BIP;
180 		ctrl &= ~MAX127_CTRL_RNG;
181 	} else {
182 		ctrl &= ~MAX127_CTRL_BIP;
183 	}
184 	data->ctrl_byte[channel] = ctrl;
185 
186 	mutex_unlock(&data->lock);
187 
188 	return 0;
189 }
190 
191 static int max127_write_max(struct max127_data *data, int channel, long val)
192 {
193 	mutex_lock(&data->lock);
194 
195 	if (val >= MAX127_FULL_RANGE)
196 		data->ctrl_byte[channel] |= MAX127_CTRL_RNG;
197 	else
198 		data->ctrl_byte[channel] &= ~MAX127_CTRL_RNG;
199 
200 	mutex_unlock(&data->lock);
201 
202 	return 0;
203 }
204 
205 static umode_t max127_is_visible(const void *_data,
206 				 enum hwmon_sensor_types type,
207 				 u32 attr, int channel)
208 {
209 	if (type == hwmon_in) {
210 		switch (attr) {
211 		case hwmon_in_input:
212 			return 0444;
213 
214 		case hwmon_in_min:
215 		case hwmon_in_max:
216 			return 0644;
217 
218 		default:
219 			break;
220 		}
221 	}
222 
223 	return 0;
224 }
225 
226 static int max127_read(struct device *dev, enum hwmon_sensor_types type,
227 			u32 attr, int channel, long *val)
228 {
229 	int status;
230 	struct max127_data *data = dev_get_drvdata(dev);
231 
232 	if (type != hwmon_in)
233 		return -EOPNOTSUPP;
234 
235 	switch (attr) {
236 	case hwmon_in_input:
237 		status = max127_read_input(data, channel, val);
238 		break;
239 
240 	case hwmon_in_min:
241 		status = max127_read_min(data, channel, val);
242 		break;
243 
244 	case hwmon_in_max:
245 		status = max127_read_max(data, channel, val);
246 		break;
247 
248 	default:
249 		status = -EOPNOTSUPP;
250 		break;
251 	}
252 
253 	return status;
254 }
255 
256 static int max127_write(struct device *dev, enum hwmon_sensor_types type,
257 			u32 attr, int channel, long val)
258 {
259 	int status;
260 	struct max127_data *data = dev_get_drvdata(dev);
261 
262 	if (type != hwmon_in)
263 		return -EOPNOTSUPP;
264 
265 	switch (attr) {
266 	case hwmon_in_min:
267 		status = max127_write_min(data, channel, val);
268 		break;
269 
270 	case hwmon_in_max:
271 		status = max127_write_max(data, channel, val);
272 		break;
273 
274 	default:
275 		status = -EOPNOTSUPP;
276 		break;
277 	}
278 
279 	return status;
280 }
281 
282 static const struct hwmon_ops max127_hwmon_ops = {
283 	.is_visible = max127_is_visible,
284 	.read = max127_read,
285 	.write = max127_write,
286 };
287 
288 static const struct hwmon_channel_info *max127_info[] = {
289 	HWMON_CHANNEL_INFO(in,
290 			   HWMON_I_INPUT | HWMON_I_MIN | HWMON_I_MAX,
291 			   HWMON_I_INPUT | HWMON_I_MIN | HWMON_I_MAX,
292 			   HWMON_I_INPUT | HWMON_I_MIN | HWMON_I_MAX,
293 			   HWMON_I_INPUT | HWMON_I_MIN | HWMON_I_MAX,
294 			   HWMON_I_INPUT | HWMON_I_MIN | HWMON_I_MAX,
295 			   HWMON_I_INPUT | HWMON_I_MIN | HWMON_I_MAX,
296 			   HWMON_I_INPUT | HWMON_I_MIN | HWMON_I_MAX,
297 			   HWMON_I_INPUT | HWMON_I_MIN | HWMON_I_MAX),
298 	NULL,
299 };
300 
301 static const struct hwmon_chip_info max127_chip_info = {
302 	.ops = &max127_hwmon_ops,
303 	.info = max127_info,
304 };
305 
306 static int max127_probe(struct i2c_client *client)
307 {
308 	int i;
309 	struct device *hwmon_dev;
310 	struct max127_data *data;
311 	struct device *dev = &client->dev;
312 
313 	data = devm_kzalloc(dev, sizeof(*data), GFP_KERNEL);
314 	if (!data)
315 		return -ENOMEM;
316 
317 	data->client = client;
318 	mutex_init(&data->lock);
319 	for (i = 0; i < ARRAY_SIZE(data->ctrl_byte); i++)
320 		data->ctrl_byte[i] = (MAX127_CTRL_START |
321 				      MAX127_SET_CHANNEL(i));
322 
323 	hwmon_dev = devm_hwmon_device_register_with_info(dev, client->name,
324 							 data,
325 							 &max127_chip_info,
326 							 NULL);
327 
328 	return PTR_ERR_OR_ZERO(hwmon_dev);
329 }
330 
331 static const struct i2c_device_id max127_id[] = {
332 	{ "max127", 0 },
333 	{ }
334 };
335 MODULE_DEVICE_TABLE(i2c, max127_id);
336 
337 static struct i2c_driver max127_driver = {
338 	.class		= I2C_CLASS_HWMON,
339 	.driver = {
340 		.name	= "max127",
341 	},
342 	.probe_new	= max127_probe,
343 	.id_table	= max127_id,
344 };
345 
346 module_i2c_driver(max127_driver);
347 
348 MODULE_LICENSE("GPL");
349 MODULE_AUTHOR("Mike Choi <mikechoi@fb.com>");
350 MODULE_AUTHOR("Tao Ren <rentao.bupt@gmail.com>");
351 MODULE_DESCRIPTION("MAX127 Hardware Monitoring driver");
352