4 * Maxim max9611/max9612 high side current sense amplifier with
5 * 12-bit ADC interface.
7 * Copyright (C) 2017 Jacopo Mondi
9 * This program is free software; you can redistribute it and/or modify
10 * it under the terms of the GNU General Public License version 2 as
11 * published by the Free Software Foundation.
15 * This driver supports input common-mode voltage, current-sense
16 * amplifier with programmable gains and die temperature reading from
17 * Maxim max9611/max9612.
19 * Op-amp, analog comparator, and watchdog functionalities are not
20 * supported by this driver.
23 #include <linux/delay.h>
24 #include <linux/i2c.h>
25 #include <linux/iio/iio.h>
26 #include <linux/iio/sysfs.h>
27 #include <linux/module.h>
28 #include <linux/of_device.h>
30 #define DRIVER_NAME "max9611"
32 /* max9611 register addresses */
33 #define MAX9611_REG_CSA_DATA 0x00
34 #define MAX9611_REG_RS_DATA 0x02
35 #define MAX9611_REG_TEMP_DATA 0x08
36 #define MAX9611_REG_CTRL1 0x0a
37 #define MAX9611_REG_CTRL2 0x0b
39 /* max9611 REG1 mux configuration options */
40 #define MAX9611_MUX_MASK GENMASK(3, 0)
41 #define MAX9611_MUX_SENSE_1x 0x00
42 #define MAX9611_MUX_SENSE_4x 0x01
43 #define MAX9611_MUX_SENSE_8x 0x02
44 #define MAX9611_INPUT_VOLT 0x03
45 #define MAX9611_MUX_TEMP 0x06
47 /* max9611 voltage (both csa and input) helper macros */
48 #define MAX9611_VOLTAGE_SHIFT 0x04
49 #define MAX9611_VOLTAGE_RAW(_r) ((_r) >> MAX9611_VOLTAGE_SHIFT)
52 * max9611 current sense amplifier voltage output:
53 * LSB and offset values depends on selected gain (1x, 4x, 8x)
55 * GAIN LSB (nV) OFFSET (LSB steps)
60 * The complete formula to calculate current sense voltage is:
61 * (((adc_read >> 4) - offset) / ((1 / LSB) * 10^-3)
63 #define MAX9611_CSA_1X_LSB_nV 107500
64 #define MAX9611_CSA_4X_LSB_nV 26880
65 #define MAX9611_CSA_8X_LSB_nV 13440
67 #define MAX9611_CSA_1X_OFFS_RAW 1
68 #define MAX9611_CSA_4X_OFFS_RAW 1
69 #define MAX9611_CSA_8X_OFFS_RAW 3
72 * max9611 common input mode (CIM): LSB is 14mV, with 14mV offset at 25 C
74 * The complete formula to calculate input common voltage is:
75 * (((adc_read >> 4) * 1000) - offset) / (1 / 14 * 1000)
77 #define MAX9611_CIM_LSB_mV 14
78 #define MAX9611_CIM_OFFSET_RAW 1
81 * max9611 temperature reading: LSB is 480 milli degrees Celsius
83 * The complete formula to calculate temperature is:
84 * ((adc_read >> 7) * 1000) / (1 / 480 * 1000)
86 #define MAX9611_TEMP_MAX_POS 0x7f80
87 #define MAX9611_TEMP_MAX_NEG 0xff80
88 #define MAX9611_TEMP_MIN_NEG 0xd980
89 #define MAX9611_TEMP_MASK GENMASK(15, 7)
90 #define MAX9611_TEMP_SHIFT 0x07
91 #define MAX9611_TEMP_RAW(_r) ((_r) >> MAX9611_TEMP_SHIFT)
92 #define MAX9611_TEMP_SCALE_NUM 1000000
93 #define MAX9611_TEMP_SCALE_DIV 2083
96 * Conversion time is 2 ms (typically) at Ta=25 degreeC
97 * No maximum value is known, so play it safe.
99 #define MAX9611_CONV_TIME_US_RANGE 3000, 3300
103 struct i2c_client *i2c_client;
105 unsigned int shunt_resistor_uohm;
108 enum max9611_conf_ids {
117 * max9611_mux_conf - associate ADC mux configuration with register address
118 * where data shall be read from
120 static const unsigned int max9611_mux_conf[][2] = {
122 { MAX9611_MUX_SENSE_1x, MAX9611_REG_CSA_DATA },
124 { MAX9611_MUX_SENSE_4x, MAX9611_REG_CSA_DATA },
126 { MAX9611_MUX_SENSE_8x, MAX9611_REG_CSA_DATA },
128 { MAX9611_INPUT_VOLT, MAX9611_REG_RS_DATA },
130 { MAX9611_MUX_TEMP, MAX9611_REG_TEMP_DATA },
133 enum max9611_csa_gain {
139 enum max9611_csa_gain_params {
145 * max9611_csa_gain_conf - associate gain multiplier with LSB and
148 * Group together parameters associated with configurable gain
149 * on current sense amplifier path to ADC interface.
150 * Current sense read routine adjusts gain until it gets a meaningful
151 * value; use this structure to retrieve the correct LSB and offset values.
153 static const unsigned int max9611_gain_conf[][2] = {
154 { /* [0] CSA_GAIN_1x */
155 MAX9611_CSA_1X_LSB_nV,
156 MAX9611_CSA_1X_OFFS_RAW,
158 { /* [1] CSA_GAIN_4x */
159 MAX9611_CSA_4X_LSB_nV,
160 MAX9611_CSA_4X_OFFS_RAW,
162 { /* [2] CSA_GAIN_8x */
163 MAX9611_CSA_8X_LSB_nV,
164 MAX9611_CSA_8X_OFFS_RAW,
168 enum max9611_chan_addrs {
169 MAX9611_CHAN_VOLTAGE_INPUT,
170 MAX9611_CHAN_VOLTAGE_SENSE,
171 MAX9611_CHAN_TEMPERATURE,
172 MAX9611_CHAN_CURRENT_LOAD,
173 MAX9611_CHAN_POWER_LOAD,
176 static const struct iio_chan_spec max9611_channels[] = {
179 .info_mask_separate = BIT(IIO_CHAN_INFO_RAW) |
180 BIT(IIO_CHAN_INFO_SCALE),
181 .address = MAX9611_CHAN_TEMPERATURE,
185 .info_mask_separate = BIT(IIO_CHAN_INFO_PROCESSED),
186 .address = MAX9611_CHAN_VOLTAGE_SENSE,
192 .info_mask_separate = BIT(IIO_CHAN_INFO_RAW) |
193 BIT(IIO_CHAN_INFO_SCALE) |
194 BIT(IIO_CHAN_INFO_OFFSET),
195 .address = MAX9611_CHAN_VOLTAGE_INPUT,
201 .info_mask_separate = BIT(IIO_CHAN_INFO_PROCESSED),
202 .address = MAX9611_CHAN_CURRENT_LOAD,
206 .info_mask_separate = BIT(IIO_CHAN_INFO_PROCESSED),
207 .address = MAX9611_CHAN_POWER_LOAD
212 * max9611_read_single() - read a single value from ADC interface
214 * Data registers are 16 bit long, spread between two 8 bit registers
215 * with consecutive addresses.
216 * Configure ADC mux first, then read register at address "reg_addr".
217 * The smbus_read_word routine asks for 16 bits and the ADC is kind enough
218 * to return values from "reg_addr" and "reg_addr + 1" consecutively.
219 * Data are transmitted with big-endian ordering: MSB arrives first.
221 * @max9611: max9611 device
222 * @selector: index for mux and register configuration
223 * @raw_val: the value returned from ADC
225 static int max9611_read_single(struct max9611_dev *max9611,
226 enum max9611_conf_ids selector,
231 u8 mux_conf = max9611_mux_conf[selector][0] & MAX9611_MUX_MASK;
232 u8 reg_addr = max9611_mux_conf[selector][1];
235 * Keep mutex lock held during read-write to avoid mux register
236 * (CTRL1) re-configuration.
238 mutex_lock(&max9611->lock);
239 ret = i2c_smbus_write_byte_data(max9611->i2c_client,
240 MAX9611_REG_CTRL1, mux_conf);
242 dev_err(max9611->dev, "i2c write byte failed: 0x%2x - 0x%2x\n",
243 MAX9611_REG_CTRL1, mux_conf);
244 mutex_unlock(&max9611->lock);
248 /* need a delay here to make register configuration stabilize. */
250 usleep_range(MAX9611_CONV_TIME_US_RANGE);
252 ret = i2c_smbus_read_word_swapped(max9611->i2c_client, reg_addr);
254 dev_err(max9611->dev, "i2c read word from 0x%2x failed\n",
256 mutex_unlock(&max9611->lock);
261 mutex_unlock(&max9611->lock);
267 * max9611_read_csa_voltage() - read current sense amplifier output voltage
269 * Current sense amplifier output voltage is read through a configurable
271 * Start with plain 1x gain, and adjust gain control properly until a
272 * meaningful value is read from ADC output.
274 * @max9611: max9611 device
275 * @adc_raw: raw value read from ADC output
276 * @csa_gain: gain configuration option selector
278 static int max9611_read_csa_voltage(struct max9611_dev *max9611,
280 enum max9611_csa_gain *csa_gain)
282 enum max9611_conf_ids gain_selectors[] = {
290 for (i = 0; i < ARRAY_SIZE(gain_selectors); ++i) {
291 ret = max9611_read_single(max9611, gain_selectors[i], adc_raw);
296 *csa_gain = (enum max9611_csa_gain)gain_selectors[i];
304 static int max9611_read_raw(struct iio_dev *indio_dev,
305 struct iio_chan_spec const *chan,
306 int *val, int *val2, long mask)
308 struct max9611_dev *dev = iio_priv(indio_dev);
309 enum max9611_csa_gain gain_selector;
310 const unsigned int *csa_gain;
315 case IIO_CHAN_INFO_RAW:
317 switch (chan->address) {
318 case MAX9611_CHAN_TEMPERATURE:
319 ret = max9611_read_single(dev, CONF_TEMP,
324 *val = MAX9611_TEMP_RAW(adc_data);
327 case MAX9611_CHAN_VOLTAGE_INPUT:
328 ret = max9611_read_single(dev, CONF_IN_VOLT,
333 *val = MAX9611_VOLTAGE_RAW(adc_data);
339 case IIO_CHAN_INFO_OFFSET:
340 /* MAX9611_CHAN_VOLTAGE_INPUT */
341 *val = MAX9611_CIM_OFFSET_RAW;
345 case IIO_CHAN_INFO_SCALE:
347 switch (chan->address) {
348 case MAX9611_CHAN_TEMPERATURE:
349 *val = MAX9611_TEMP_SCALE_NUM;
350 *val2 = MAX9611_TEMP_SCALE_DIV;
352 return IIO_VAL_FRACTIONAL;
354 case MAX9611_CHAN_VOLTAGE_INPUT:
355 *val = MAX9611_CIM_LSB_mV;
362 case IIO_CHAN_INFO_PROCESSED:
364 switch (chan->address) {
365 case MAX9611_CHAN_VOLTAGE_SENSE:
367 * processed (mV): (raw - offset) * LSB (nV) / 10^6
369 * Even if max9611 can output raw csa voltage readings,
370 * use a produced value as scale depends on gain.
372 ret = max9611_read_csa_voltage(dev, &adc_data,
377 csa_gain = max9611_gain_conf[gain_selector];
379 adc_data -= csa_gain[CSA_GAIN_OFFS_RAW];
380 *val = MAX9611_VOLTAGE_RAW(adc_data) *
381 csa_gain[CSA_GAIN_LSB_nV];
384 return IIO_VAL_FRACTIONAL;
386 case MAX9611_CHAN_CURRENT_LOAD:
387 /* processed (mA): Vcsa (nV) / Rshunt (uOhm) */
388 ret = max9611_read_csa_voltage(dev, &adc_data,
393 csa_gain = max9611_gain_conf[gain_selector];
395 adc_data -= csa_gain[CSA_GAIN_OFFS_RAW];
396 *val = MAX9611_VOLTAGE_RAW(adc_data) *
397 csa_gain[CSA_GAIN_LSB_nV];
398 *val2 = dev->shunt_resistor_uohm;
400 return IIO_VAL_FRACTIONAL;
402 case MAX9611_CHAN_POWER_LOAD:
404 * processed (mW): Vin (mV) * Vcsa (uV) /
407 ret = max9611_read_single(dev, CONF_IN_VOLT,
412 adc_data -= MAX9611_CIM_OFFSET_RAW;
413 *val = MAX9611_VOLTAGE_RAW(adc_data) *
416 ret = max9611_read_csa_voltage(dev, &adc_data,
421 csa_gain = max9611_gain_conf[gain_selector];
423 /* divide by 10^3 here to avoid 32bit overflow */
424 adc_data -= csa_gain[CSA_GAIN_OFFS_RAW];
425 *val *= MAX9611_VOLTAGE_RAW(adc_data) *
426 csa_gain[CSA_GAIN_LSB_nV] / 1000;
427 *val2 = dev->shunt_resistor_uohm;
429 return IIO_VAL_FRACTIONAL;
438 static ssize_t max9611_shunt_resistor_show(struct device *dev,
439 struct device_attribute *attr,
442 struct max9611_dev *max9611 = iio_priv(dev_to_iio_dev(dev));
445 i = max9611->shunt_resistor_uohm / 1000000;
446 r = max9611->shunt_resistor_uohm % 1000000;
448 return sprintf(buf, "%u.%06u\n", i, r);
451 static IIO_DEVICE_ATTR(in_power_shunt_resistor, 0444,
452 max9611_shunt_resistor_show, NULL, 0);
453 static IIO_DEVICE_ATTR(in_current_shunt_resistor, 0444,
454 max9611_shunt_resistor_show, NULL, 0);
456 static struct attribute *max9611_attributes[] = {
457 &iio_dev_attr_in_power_shunt_resistor.dev_attr.attr,
458 &iio_dev_attr_in_current_shunt_resistor.dev_attr.attr,
462 static const struct attribute_group max9611_attribute_group = {
463 .attrs = max9611_attributes,
466 static const struct iio_info indio_info = {
467 .driver_module = THIS_MODULE,
468 .read_raw = max9611_read_raw,
469 .attrs = &max9611_attribute_group,
472 static int max9611_init(struct max9611_dev *max9611)
474 struct i2c_client *client = max9611->i2c_client;
478 if (!i2c_check_functionality(client->adapter,
479 I2C_FUNC_SMBUS_WRITE_BYTE |
480 I2C_FUNC_SMBUS_READ_WORD_DATA)) {
481 dev_err(max9611->dev,
482 "I2c adapter does not support smbus write_byte or read_word functionalities: aborting probe.\n");
486 /* Make sure die temperature is in range to test communications. */
487 ret = max9611_read_single(max9611, CONF_TEMP, ®val);
491 regval &= MAX9611_TEMP_MASK;
493 if ((regval > MAX9611_TEMP_MAX_POS &&
494 regval < MAX9611_TEMP_MIN_NEG) ||
495 regval > MAX9611_TEMP_MAX_NEG) {
496 dev_err(max9611->dev,
497 "Invalid value received from ADC 0x%4x: aborting\n",
502 /* Mux shall be zeroed back before applying other configurations */
503 ret = i2c_smbus_write_byte_data(max9611->i2c_client,
504 MAX9611_REG_CTRL1, 0);
506 dev_err(max9611->dev, "i2c write byte failed: 0x%2x - 0x%2x\n",
507 MAX9611_REG_CTRL1, 0);
511 ret = i2c_smbus_write_byte_data(max9611->i2c_client,
512 MAX9611_REG_CTRL2, 0);
514 dev_err(max9611->dev, "i2c write byte failed: 0x%2x - 0x%2x\n",
515 MAX9611_REG_CTRL2, 0);
518 usleep_range(MAX9611_CONV_TIME_US_RANGE);
523 static const struct of_device_id max9611_of_table[] = {
524 {.compatible = "maxim,max9611", .data = "max9611"},
525 {.compatible = "maxim,max9612", .data = "max9612"},
529 MODULE_DEVICE_TABLE(of, max9611_of_table);
530 static int max9611_probe(struct i2c_client *client,
531 const struct i2c_device_id *id)
533 const char * const shunt_res_prop = "shunt-resistor-micro-ohms";
534 const struct device_node *of_node = client->dev.of_node;
535 const struct of_device_id *of_id =
536 of_match_device(max9611_of_table, &client->dev);
537 struct max9611_dev *max9611;
538 struct iio_dev *indio_dev;
539 unsigned int of_shunt;
542 indio_dev = devm_iio_device_alloc(&client->dev, sizeof(*max9611));
546 i2c_set_clientdata(client, indio_dev);
548 max9611 = iio_priv(indio_dev);
549 max9611->dev = &client->dev;
550 max9611->i2c_client = client;
551 mutex_init(&max9611->lock);
553 ret = of_property_read_u32(of_node, shunt_res_prop, &of_shunt);
555 dev_err(&client->dev,
556 "Missing %s property for %pOF node\n",
557 shunt_res_prop, of_node);
560 max9611->shunt_resistor_uohm = of_shunt;
562 ret = max9611_init(max9611);
566 indio_dev->dev.parent = &client->dev;
567 indio_dev->dev.of_node = client->dev.of_node;
568 indio_dev->name = of_id->data;
569 indio_dev->modes = INDIO_DIRECT_MODE;
570 indio_dev->info = &indio_info;
571 indio_dev->channels = max9611_channels;
572 indio_dev->num_channels = ARRAY_SIZE(max9611_channels);
574 return devm_iio_device_register(&client->dev, indio_dev);
577 static struct i2c_driver max9611_driver = {
580 .owner = THIS_MODULE,
581 .of_match_table = max9611_of_table,
583 .probe = max9611_probe,
585 module_i2c_driver(max9611_driver);
587 MODULE_AUTHOR("Jacopo Mondi <jacopo+renesas@jmondi.org>");
588 MODULE_DESCRIPTION("Maxim max9611/12 current sense amplifier with 12bit ADC");
589 MODULE_LICENSE("GPL v2");