1 // SPDX-License-Identifier: GPL-2.0
5 * Maxim max9611/max9612 high side current sense amplifier with
6 * 12-bit ADC interface.
8 * Copyright (C) 2017 Jacopo Mondi
12 * This driver supports input common-mode voltage, current-sense
13 * amplifier with programmable gains and die temperature reading from
14 * Maxim max9611/max9612.
16 * Op-amp, analog comparator, and watchdog functionalities are not
17 * supported by this driver.
20 #include <linux/delay.h>
21 #include <linux/i2c.h>
22 #include <linux/iio/iio.h>
23 #include <linux/iio/sysfs.h>
24 #include <linux/module.h>
25 #include <linux/of_device.h>
27 #define DRIVER_NAME "max9611"
29 /* max9611 register addresses */
30 #define MAX9611_REG_CSA_DATA 0x00
31 #define MAX9611_REG_RS_DATA 0x02
32 #define MAX9611_REG_TEMP_DATA 0x08
33 #define MAX9611_REG_CTRL1 0x0a
34 #define MAX9611_REG_CTRL2 0x0b
36 /* max9611 REG1 mux configuration options */
37 #define MAX9611_MUX_MASK GENMASK(3, 0)
38 #define MAX9611_MUX_SENSE_1x 0x00
39 #define MAX9611_MUX_SENSE_4x 0x01
40 #define MAX9611_MUX_SENSE_8x 0x02
41 #define MAX9611_INPUT_VOLT 0x03
42 #define MAX9611_MUX_TEMP 0x06
44 /* max9611 voltage (both csa and input) helper macros */
45 #define MAX9611_VOLTAGE_SHIFT 0x04
46 #define MAX9611_VOLTAGE_RAW(_r) ((_r) >> MAX9611_VOLTAGE_SHIFT)
49 * max9611 current sense amplifier voltage output:
50 * LSB and offset values depends on selected gain (1x, 4x, 8x)
52 * GAIN LSB (nV) OFFSET (LSB steps)
57 * The complete formula to calculate current sense voltage is:
58 * (((adc_read >> 4) - offset) / ((1 / LSB) * 10^-3)
60 #define MAX9611_CSA_1X_LSB_nV 107500
61 #define MAX9611_CSA_4X_LSB_nV 26880
62 #define MAX9611_CSA_8X_LSB_nV 13440
64 #define MAX9611_CSA_1X_OFFS_RAW 1
65 #define MAX9611_CSA_4X_OFFS_RAW 1
66 #define MAX9611_CSA_8X_OFFS_RAW 3
69 * max9611 common input mode (CIM): LSB is 14mV, with 14mV offset at 25 C
71 * The complete formula to calculate input common voltage is:
72 * (((adc_read >> 4) * 1000) - offset) / (1 / 14 * 1000)
74 #define MAX9611_CIM_LSB_mV 14
75 #define MAX9611_CIM_OFFSET_RAW 1
78 * max9611 temperature reading: LSB is 480 milli degrees Celsius
80 * The complete formula to calculate temperature is:
81 * ((adc_read >> 7) * 1000) / (1 / 480 * 1000)
83 #define MAX9611_TEMP_MAX_POS 0x7f80
84 #define MAX9611_TEMP_MAX_NEG 0xff80
85 #define MAX9611_TEMP_MIN_NEG 0xd980
86 #define MAX9611_TEMP_MASK GENMASK(15, 7)
87 #define MAX9611_TEMP_SHIFT 0x07
88 #define MAX9611_TEMP_RAW(_r) ((_r) >> MAX9611_TEMP_SHIFT)
89 #define MAX9611_TEMP_SCALE_NUM 1000000
90 #define MAX9611_TEMP_SCALE_DIV 2083
93 * Conversion time is 2 ms (typically) at Ta=25 degreeC
94 * No maximum value is known, so play it safe.
96 #define MAX9611_CONV_TIME_US_RANGE 3000, 3300
100 struct i2c_client *i2c_client;
102 unsigned int shunt_resistor_uohm;
105 enum max9611_conf_ids {
114 * max9611_mux_conf - associate ADC mux configuration with register address
115 * where data shall be read from
117 static const unsigned int max9611_mux_conf[][2] = {
119 { MAX9611_MUX_SENSE_1x, MAX9611_REG_CSA_DATA },
121 { MAX9611_MUX_SENSE_4x, MAX9611_REG_CSA_DATA },
123 { MAX9611_MUX_SENSE_8x, MAX9611_REG_CSA_DATA },
125 { MAX9611_INPUT_VOLT, MAX9611_REG_RS_DATA },
127 { MAX9611_MUX_TEMP, MAX9611_REG_TEMP_DATA },
130 enum max9611_csa_gain {
136 enum max9611_csa_gain_params {
142 * max9611_csa_gain_conf - associate gain multiplier with LSB and
145 * Group together parameters associated with configurable gain
146 * on current sense amplifier path to ADC interface.
147 * Current sense read routine adjusts gain until it gets a meaningful
148 * value; use this structure to retrieve the correct LSB and offset values.
150 static const unsigned int max9611_gain_conf[][2] = {
151 { /* [0] CSA_GAIN_1x */
152 MAX9611_CSA_1X_LSB_nV,
153 MAX9611_CSA_1X_OFFS_RAW,
155 { /* [1] CSA_GAIN_4x */
156 MAX9611_CSA_4X_LSB_nV,
157 MAX9611_CSA_4X_OFFS_RAW,
159 { /* [2] CSA_GAIN_8x */
160 MAX9611_CSA_8X_LSB_nV,
161 MAX9611_CSA_8X_OFFS_RAW,
165 enum max9611_chan_addrs {
166 MAX9611_CHAN_VOLTAGE_INPUT,
167 MAX9611_CHAN_VOLTAGE_SENSE,
168 MAX9611_CHAN_TEMPERATURE,
169 MAX9611_CHAN_CURRENT_LOAD,
170 MAX9611_CHAN_POWER_LOAD,
173 static const struct iio_chan_spec max9611_channels[] = {
176 .info_mask_separate = BIT(IIO_CHAN_INFO_RAW) |
177 BIT(IIO_CHAN_INFO_SCALE),
178 .address = MAX9611_CHAN_TEMPERATURE,
182 .info_mask_separate = BIT(IIO_CHAN_INFO_PROCESSED),
183 .address = MAX9611_CHAN_VOLTAGE_SENSE,
189 .info_mask_separate = BIT(IIO_CHAN_INFO_RAW) |
190 BIT(IIO_CHAN_INFO_SCALE) |
191 BIT(IIO_CHAN_INFO_OFFSET),
192 .address = MAX9611_CHAN_VOLTAGE_INPUT,
198 .info_mask_separate = BIT(IIO_CHAN_INFO_PROCESSED),
199 .address = MAX9611_CHAN_CURRENT_LOAD,
203 .info_mask_separate = BIT(IIO_CHAN_INFO_PROCESSED),
204 .address = MAX9611_CHAN_POWER_LOAD
209 * max9611_read_single() - read a single value from ADC interface
211 * Data registers are 16 bit long, spread between two 8 bit registers
212 * with consecutive addresses.
213 * Configure ADC mux first, then read register at address "reg_addr".
214 * The smbus_read_word routine asks for 16 bits and the ADC is kind enough
215 * to return values from "reg_addr" and "reg_addr + 1" consecutively.
216 * Data are transmitted with big-endian ordering: MSB arrives first.
218 * @max9611: max9611 device
219 * @selector: index for mux and register configuration
220 * @raw_val: the value returned from ADC
222 static int max9611_read_single(struct max9611_dev *max9611,
223 enum max9611_conf_ids selector,
228 u8 mux_conf = max9611_mux_conf[selector][0] & MAX9611_MUX_MASK;
229 u8 reg_addr = max9611_mux_conf[selector][1];
232 * Keep mutex lock held during read-write to avoid mux register
233 * (CTRL1) re-configuration.
235 mutex_lock(&max9611->lock);
236 ret = i2c_smbus_write_byte_data(max9611->i2c_client,
237 MAX9611_REG_CTRL1, mux_conf);
239 dev_err(max9611->dev, "i2c write byte failed: 0x%2x - 0x%2x\n",
240 MAX9611_REG_CTRL1, mux_conf);
241 mutex_unlock(&max9611->lock);
245 /* need a delay here to make register configuration stabilize. */
247 usleep_range(MAX9611_CONV_TIME_US_RANGE);
249 ret = i2c_smbus_read_word_swapped(max9611->i2c_client, reg_addr);
251 dev_err(max9611->dev, "i2c read word from 0x%2x failed\n",
253 mutex_unlock(&max9611->lock);
258 mutex_unlock(&max9611->lock);
264 * max9611_read_csa_voltage() - read current sense amplifier output voltage
266 * Current sense amplifier output voltage is read through a configurable
268 * Start with plain 1x gain, and adjust gain control properly until a
269 * meaningful value is read from ADC output.
271 * @max9611: max9611 device
272 * @adc_raw: raw value read from ADC output
273 * @csa_gain: gain configuration option selector
275 static int max9611_read_csa_voltage(struct max9611_dev *max9611,
277 enum max9611_csa_gain *csa_gain)
279 enum max9611_conf_ids gain_selectors[] = {
287 for (i = 0; i < ARRAY_SIZE(gain_selectors); ++i) {
288 ret = max9611_read_single(max9611, gain_selectors[i], adc_raw);
293 *csa_gain = (enum max9611_csa_gain)gain_selectors[i];
301 static int max9611_read_raw(struct iio_dev *indio_dev,
302 struct iio_chan_spec const *chan,
303 int *val, int *val2, long mask)
305 struct max9611_dev *dev = iio_priv(indio_dev);
306 enum max9611_csa_gain gain_selector;
307 const unsigned int *csa_gain;
312 case IIO_CHAN_INFO_RAW:
314 switch (chan->address) {
315 case MAX9611_CHAN_TEMPERATURE:
316 ret = max9611_read_single(dev, CONF_TEMP,
321 *val = MAX9611_TEMP_RAW(adc_data);
324 case MAX9611_CHAN_VOLTAGE_INPUT:
325 ret = max9611_read_single(dev, CONF_IN_VOLT,
330 *val = MAX9611_VOLTAGE_RAW(adc_data);
336 case IIO_CHAN_INFO_OFFSET:
337 /* MAX9611_CHAN_VOLTAGE_INPUT */
338 *val = MAX9611_CIM_OFFSET_RAW;
342 case IIO_CHAN_INFO_SCALE:
344 switch (chan->address) {
345 case MAX9611_CHAN_TEMPERATURE:
346 *val = MAX9611_TEMP_SCALE_NUM;
347 *val2 = MAX9611_TEMP_SCALE_DIV;
349 return IIO_VAL_FRACTIONAL;
351 case MAX9611_CHAN_VOLTAGE_INPUT:
352 *val = MAX9611_CIM_LSB_mV;
359 case IIO_CHAN_INFO_PROCESSED:
361 switch (chan->address) {
362 case MAX9611_CHAN_VOLTAGE_SENSE:
364 * processed (mV): (raw - offset) * LSB (nV) / 10^6
366 * Even if max9611 can output raw csa voltage readings,
367 * use a produced value as scale depends on gain.
369 ret = max9611_read_csa_voltage(dev, &adc_data,
374 csa_gain = max9611_gain_conf[gain_selector];
376 adc_data -= csa_gain[CSA_GAIN_OFFS_RAW];
377 *val = MAX9611_VOLTAGE_RAW(adc_data) *
378 csa_gain[CSA_GAIN_LSB_nV];
381 return IIO_VAL_FRACTIONAL;
383 case MAX9611_CHAN_CURRENT_LOAD:
384 /* processed (mA): Vcsa (nV) / Rshunt (uOhm) */
385 ret = max9611_read_csa_voltage(dev, &adc_data,
390 csa_gain = max9611_gain_conf[gain_selector];
392 adc_data -= csa_gain[CSA_GAIN_OFFS_RAW];
393 *val = MAX9611_VOLTAGE_RAW(adc_data) *
394 csa_gain[CSA_GAIN_LSB_nV];
395 *val2 = dev->shunt_resistor_uohm;
397 return IIO_VAL_FRACTIONAL;
399 case MAX9611_CHAN_POWER_LOAD:
401 * processed (mW): Vin (mV) * Vcsa (uV) /
404 ret = max9611_read_single(dev, CONF_IN_VOLT,
409 adc_data -= MAX9611_CIM_OFFSET_RAW;
410 *val = MAX9611_VOLTAGE_RAW(adc_data) *
413 ret = max9611_read_csa_voltage(dev, &adc_data,
418 csa_gain = max9611_gain_conf[gain_selector];
420 /* divide by 10^3 here to avoid 32bit overflow */
421 adc_data -= csa_gain[CSA_GAIN_OFFS_RAW];
422 *val *= MAX9611_VOLTAGE_RAW(adc_data) *
423 csa_gain[CSA_GAIN_LSB_nV] / 1000;
424 *val2 = dev->shunt_resistor_uohm;
426 return IIO_VAL_FRACTIONAL;
435 static ssize_t max9611_shunt_resistor_show(struct device *dev,
436 struct device_attribute *attr,
439 struct max9611_dev *max9611 = iio_priv(dev_to_iio_dev(dev));
442 i = max9611->shunt_resistor_uohm / 1000000;
443 r = max9611->shunt_resistor_uohm % 1000000;
445 return sprintf(buf, "%u.%06u\n", i, r);
448 static IIO_DEVICE_ATTR(in_power_shunt_resistor, 0444,
449 max9611_shunt_resistor_show, NULL, 0);
450 static IIO_DEVICE_ATTR(in_current_shunt_resistor, 0444,
451 max9611_shunt_resistor_show, NULL, 0);
453 static struct attribute *max9611_attributes[] = {
454 &iio_dev_attr_in_power_shunt_resistor.dev_attr.attr,
455 &iio_dev_attr_in_current_shunt_resistor.dev_attr.attr,
459 static const struct attribute_group max9611_attribute_group = {
460 .attrs = max9611_attributes,
463 static const struct iio_info indio_info = {
464 .read_raw = max9611_read_raw,
465 .attrs = &max9611_attribute_group,
468 static int max9611_init(struct max9611_dev *max9611)
470 struct i2c_client *client = max9611->i2c_client;
474 if (!i2c_check_functionality(client->adapter,
475 I2C_FUNC_SMBUS_WRITE_BYTE |
476 I2C_FUNC_SMBUS_READ_WORD_DATA)) {
477 dev_err(max9611->dev,
478 "I2c adapter does not support smbus write_byte or read_word functionalities: aborting probe.\n");
482 /* Make sure die temperature is in range to test communications. */
483 ret = max9611_read_single(max9611, CONF_TEMP, ®val);
487 regval &= MAX9611_TEMP_MASK;
489 if ((regval > MAX9611_TEMP_MAX_POS &&
490 regval < MAX9611_TEMP_MIN_NEG) ||
491 regval > MAX9611_TEMP_MAX_NEG) {
492 dev_err(max9611->dev,
493 "Invalid value received from ADC 0x%4x: aborting\n",
498 /* Mux shall be zeroed back before applying other configurations */
499 ret = i2c_smbus_write_byte_data(max9611->i2c_client,
500 MAX9611_REG_CTRL1, 0);
502 dev_err(max9611->dev, "i2c write byte failed: 0x%2x - 0x%2x\n",
503 MAX9611_REG_CTRL1, 0);
507 ret = i2c_smbus_write_byte_data(max9611->i2c_client,
508 MAX9611_REG_CTRL2, 0);
510 dev_err(max9611->dev, "i2c write byte failed: 0x%2x - 0x%2x\n",
511 MAX9611_REG_CTRL2, 0);
514 usleep_range(MAX9611_CONV_TIME_US_RANGE);
519 static const struct of_device_id max9611_of_table[] = {
520 {.compatible = "maxim,max9611", .data = "max9611"},
521 {.compatible = "maxim,max9612", .data = "max9612"},
525 MODULE_DEVICE_TABLE(of, max9611_of_table);
526 static int max9611_probe(struct i2c_client *client,
527 const struct i2c_device_id *id)
529 const char * const shunt_res_prop = "shunt-resistor-micro-ohms";
530 const struct device_node *of_node = client->dev.of_node;
531 const struct of_device_id *of_id =
532 of_match_device(max9611_of_table, &client->dev);
533 struct max9611_dev *max9611;
534 struct iio_dev *indio_dev;
535 unsigned int of_shunt;
538 indio_dev = devm_iio_device_alloc(&client->dev, sizeof(*max9611));
542 i2c_set_clientdata(client, indio_dev);
544 max9611 = iio_priv(indio_dev);
545 max9611->dev = &client->dev;
546 max9611->i2c_client = client;
547 mutex_init(&max9611->lock);
549 ret = of_property_read_u32(of_node, shunt_res_prop, &of_shunt);
551 dev_err(&client->dev,
552 "Missing %s property for %pOF node\n",
553 shunt_res_prop, of_node);
556 max9611->shunt_resistor_uohm = of_shunt;
558 ret = max9611_init(max9611);
562 indio_dev->dev.parent = &client->dev;
563 indio_dev->dev.of_node = client->dev.of_node;
564 indio_dev->name = of_id->data;
565 indio_dev->modes = INDIO_DIRECT_MODE;
566 indio_dev->info = &indio_info;
567 indio_dev->channels = max9611_channels;
568 indio_dev->num_channels = ARRAY_SIZE(max9611_channels);
570 return devm_iio_device_register(&client->dev, indio_dev);
573 static struct i2c_driver max9611_driver = {
576 .of_match_table = max9611_of_table,
578 .probe = max9611_probe,
580 module_i2c_driver(max9611_driver);
582 MODULE_AUTHOR("Jacopo Mondi <jacopo+renesas@jmondi.org>");
583 MODULE_DESCRIPTION("Maxim max9611/12 current sense amplifier with 12bit ADC");
584 MODULE_LICENSE("GPL v2");