src/kernel/linux/v4.19/drivers/hwmon/pmbus/max31785.c - T800 - Gitiles

 /*
  * Copyright (C) 2017 IBM Corp.
  *
  * This program is free software; you can redistribute it and/or modify
  * it under the terms of the GNU General Public License as published by
  * the Free Software Foundation; either version 2 of the License, or
  * (at your option) any later version.
  */

 #include <linux/kernel.h>
 #include <linux/module.h>
 #include <linux/init.h>
 #include <linux/err.h>
 #include <linux/i2c.h>
 #include "pmbus.h"

 enum max31785_regs {
 	MFR_REVISION		= 0x9b,
 	MFR_FAN_CONFIG		= 0xf1,
 };

 #define MAX31785			0x3030
 #define MAX31785A			0x3040

 #define MFR_FAN_CONFIG_DUAL_TACH	BIT(12)

 #define MAX31785_NR_PAGES		23
 #define MAX31785_NR_FAN_PAGES		6

 static int max31785_read_byte_data(struct i2c_client *client, int page,
 				   int reg)
 {
 	if (page < MAX31785_NR_PAGES)
 		return -ENODATA;

 	switch (reg) {
 	case PMBUS_VOUT_MODE:
 		return -ENOTSUPP;
 	case PMBUS_FAN_CONFIG_12:
 		return pmbus_read_byte_data(client, page - MAX31785_NR_PAGES,
 					    reg);
 	}

 	return -ENODATA;
 }

 static int max31785_write_byte(struct i2c_client *client, int page, u8 value)
 {
 	if (page < MAX31785_NR_PAGES)
 		return -ENODATA;

 	return -ENOTSUPP;
 }

 static int max31785_read_long_data(struct i2c_client *client, int page,
 				   int reg, u32 *data)
 {
 	unsigned char cmdbuf[1];
 	unsigned char rspbuf[4];
 	int rc;

 	struct i2c_msg msg[2] = {
 		{
 			.addr = client->addr,
 			.flags = 0,
 			.len = sizeof(cmdbuf),
 			.buf = cmdbuf,
 		},
 		{
 			.addr = client->addr,
 			.flags = I2C_M_RD,
 			.len = sizeof(rspbuf),
 			.buf = rspbuf,
 		},
 	};

 	cmdbuf[0] = reg;

 	rc = pmbus_set_page(client, page);
 	if (rc < 0)
 		return rc;

 	rc = i2c_transfer(client->adapter, msg, ARRAY_SIZE(msg));
 	if (rc < 0)
 		return rc;

 	*data = (rspbuf[0] << (0 * 8)) | (rspbuf[1] << (1 * 8)) |
 		(rspbuf[2] << (2 * 8)) | (rspbuf[3] << (3 * 8));

 	return rc;
 }

 static int max31785_get_pwm(struct i2c_client *client, int page)
 {
 	int rv;

 	rv = pmbus_get_fan_rate_device(client, page, 0, percent);
 	if (rv < 0)
 		return rv;
 	else if (rv >= 0x8000)
 		return 0;
 	else if (rv >= 0x2711)
 		return 0x2710;

 	return rv;
 }

 static int max31785_get_pwm_mode(struct i2c_client *client, int page)
 {
 	int config;
 	int command;

 	config = pmbus_read_byte_data(client, page, PMBUS_FAN_CONFIG_12);
 	if (config < 0)
 		return config;

 	command = pmbus_read_word_data(client, page, PMBUS_FAN_COMMAND_1);
 	if (command < 0)
 		return command;

 	if (config & PB_FAN_1_RPM)
 		return (command >= 0x8000) ? 3 : 2;

 	if (command >= 0x8000)
 		return 3;
 	else if (command >= 0x2711)
 		return 0;

 	return 1;
 }

 static int max31785_read_word_data(struct i2c_client *client, int page,
 				   int reg)
 {
 	u32 val;
 	int rv;

 	switch (reg) {
 	case PMBUS_READ_FAN_SPEED_1:
 		if (page < MAX31785_NR_PAGES)
 			return -ENODATA;

 		rv = max31785_read_long_data(client, page - MAX31785_NR_PAGES,
 					     reg, &val);
 		if (rv < 0)
 			return rv;

 		rv = (val >> 16) & 0xffff;
 		break;
 	case PMBUS_FAN_COMMAND_1:
 		/*
 		 * PMBUS_FAN_COMMAND_x is probed to judge whether or not to
 		 * expose fan control registers.
 		 *
 		 * Don't expose fan_target attribute for virtual pages.
 		 */
 		rv = (page >= MAX31785_NR_PAGES) ? -ENOTSUPP : -ENODATA;
 		break;
 	case PMBUS_VIRT_PWM_1:
 		rv = max31785_get_pwm(client, page);
 		break;
 	case PMBUS_VIRT_PWM_ENABLE_1:
 		rv = max31785_get_pwm_mode(client, page);
 		break;
 	default:
 		rv = -ENODATA;
 		break;
 	}

 	return rv;
 }

 static inline u32 max31785_scale_pwm(u32 sensor_val)
 {
 	/*
 	 * The datasheet describes the accepted value range for manual PWM as
 	 * [0, 0x2710], while the hwmon pwmX sysfs interface accepts values in
 	 * [0, 255]. The MAX31785 uses DIRECT mode to scale the FAN_COMMAND
 	 * registers and in PWM mode the coefficients are m=1, b=0, R=2. The
 	 * important observation here is that 0x2710 == 10000 == 100 * 100.
 	 *
 	 * R=2 (== 10^2 == 100) accounts for scaling the value provided at the
 	 * sysfs interface into the required hardware resolution, but it does
 	 * not yet yield a value that we can write to the device (this initial
 	 * scaling is handled by pmbus_data2reg()). Multiplying by 100 below
 	 * translates the parameter value into the percentage units required by
 	 * PMBus, and then we scale back by 255 as required by the hwmon pwmX
 	 * interface to yield the percentage value at the appropriate
 	 * resolution for hardware.
 	 */
 	return (sensor_val * 100) / 255;
 }

 static int max31785_pwm_enable(struct i2c_client *client, int page,
 				    u16 word)
 {
 	int config = 0;
 	int rate;

 	switch (word) {
 	case 0:
 		rate = 0x7fff;
 		break;
 	case 1:
 		rate = pmbus_get_fan_rate_cached(client, page, 0, percent);
 		if (rate < 0)
 			return rate;
 		rate = max31785_scale_pwm(rate);
 		break;
 	case 2:
 		config = PB_FAN_1_RPM;
 		rate = pmbus_get_fan_rate_cached(client, page, 0, rpm);
 		if (rate < 0)
 			return rate;
 		break;
 	case 3:
 		rate = 0xffff;
 		break;
 	default:
 		return -EINVAL;
 	}

 	return pmbus_update_fan(client, page, 0, config, PB_FAN_1_RPM, rate);
 }

 static int max31785_write_word_data(struct i2c_client *client, int page,
 				    int reg, u16 word)
 {
 	switch (reg) {
 	case PMBUS_VIRT_PWM_1:
 		return pmbus_update_fan(client, page, 0, 0, PB_FAN_1_RPM,
 					max31785_scale_pwm(word));
 	case PMBUS_VIRT_PWM_ENABLE_1:
 		return max31785_pwm_enable(client, page, word);
 	default:
 		break;
 	}

 	return -ENODATA;
 }

 #define MAX31785_FAN_FUNCS \
 	(PMBUS_HAVE_FAN12 | PMBUS_HAVE_STATUS_FAN12 | PMBUS_HAVE_PWM12)

 #define MAX31785_TEMP_FUNCS \
 	(PMBUS_HAVE_TEMP | PMBUS_HAVE_STATUS_TEMP)

 #define MAX31785_VOUT_FUNCS \
 	(PMBUS_HAVE_VOUT | PMBUS_HAVE_STATUS_VOUT)

 #define MAX37185_NUM_FAN_PAGES 6

 static const struct pmbus_driver_info max31785_info = {
 	.pages = MAX31785_NR_PAGES,

 	.write_word_data = max31785_write_word_data,
 	.read_byte_data = max31785_read_byte_data,
 	.read_word_data = max31785_read_word_data,
 	.write_byte = max31785_write_byte,

 	/* RPM */
 	.format[PSC_FAN] = direct,
 	.m[PSC_FAN] = 1,
 	.b[PSC_FAN] = 0,
 	.R[PSC_FAN] = 0,
 	/* PWM */
 	.format[PSC_PWM] = direct,
 	.m[PSC_PWM] = 1,
 	.b[PSC_PWM] = 0,
 	.R[PSC_PWM] = 2,
 	.func[0] = MAX31785_FAN_FUNCS,
 	.func[1] = MAX31785_FAN_FUNCS,
 	.func[2] = MAX31785_FAN_FUNCS,
 	.func[3] = MAX31785_FAN_FUNCS,
 	.func[4] = MAX31785_FAN_FUNCS,
 	.func[5] = MAX31785_FAN_FUNCS,

 	.format[PSC_TEMPERATURE] = direct,
 	.m[PSC_TEMPERATURE] = 1,
 	.b[PSC_TEMPERATURE] = 0,
 	.R[PSC_TEMPERATURE] = 2,
 	.func[6]  = MAX31785_TEMP_FUNCS,
 	.func[7]  = MAX31785_TEMP_FUNCS,
 	.func[8]  = MAX31785_TEMP_FUNCS,
 	.func[9]  = MAX31785_TEMP_FUNCS,
 	.func[10] = MAX31785_TEMP_FUNCS,
 	.func[11] = MAX31785_TEMP_FUNCS,
 	.func[12] = MAX31785_TEMP_FUNCS,
 	.func[13] = MAX31785_TEMP_FUNCS,
 	.func[14] = MAX31785_TEMP_FUNCS,
 	.func[15] = MAX31785_TEMP_FUNCS,
 	.func[16] = MAX31785_TEMP_FUNCS,

 	.format[PSC_VOLTAGE_OUT] = direct,
 	.m[PSC_VOLTAGE_OUT] = 1,
 	.b[PSC_VOLTAGE_OUT] = 0,
 	.R[PSC_VOLTAGE_OUT] = 0,
 	.func[17] = MAX31785_VOUT_FUNCS,
 	.func[18] = MAX31785_VOUT_FUNCS,
 	.func[19] = MAX31785_VOUT_FUNCS,
 	.func[20] = MAX31785_VOUT_FUNCS,
 	.func[21] = MAX31785_VOUT_FUNCS,
 	.func[22] = MAX31785_VOUT_FUNCS,
 };

 static int max31785_configure_dual_tach(struct i2c_client *client,
 					struct pmbus_driver_info *info)
 {
 	int ret;
 	int i;

 	for (i = 0; i < MAX31785_NR_FAN_PAGES; i++) {
 		ret = i2c_smbus_write_byte_data(client, PMBUS_PAGE, i);
 		if (ret < 0)
 			return ret;

 		ret = i2c_smbus_read_word_data(client, MFR_FAN_CONFIG);
 		if (ret < 0)
 			return ret;

 		if (ret & MFR_FAN_CONFIG_DUAL_TACH) {
 			int virtual = MAX31785_NR_PAGES + i;

 			info->pages = virtual + 1;
 			info->func[virtual] |= PMBUS_HAVE_FAN12;
 			info->func[virtual] |= PMBUS_PAGE_VIRTUAL;
 		}
 	}

 	return 0;
 }

 static int max31785_probe(struct i2c_client *client,
 			  const struct i2c_device_id *id)
 {
 	struct device *dev = &client->dev;
 	struct pmbus_driver_info *info;
 	bool dual_tach = false;
 	s64 ret;

 	if (!i2c_check_functionality(client->adapter,
 				     I2C_FUNC_SMBUS_BYTE_DATA |
 				     I2C_FUNC_SMBUS_WORD_DATA))
 		return -ENODEV;

 	info = devm_kzalloc(dev, sizeof(struct pmbus_driver_info), GFP_KERNEL);
 	if (!info)
 		return -ENOMEM;

 	*info = max31785_info;

 	ret = i2c_smbus_write_byte_data(client, PMBUS_PAGE, 255);
 	if (ret < 0)
 		return ret;

 	ret = i2c_smbus_read_word_data(client, MFR_REVISION);
 	if (ret < 0)
 		return ret;

 	if (ret == MAX31785A) {
 		dual_tach = true;
 	} else if (ret == MAX31785) {
 		if (!strcmp("max31785a", id->name))
 			dev_warn(dev, "Expected max3175a, found max31785: cannot provide secondary tachometer readings\n");
 	} else {
 		return -ENODEV;
 	}

 	if (dual_tach) {
 		ret = max31785_configure_dual_tach(client, info);
 		if (ret < 0)
 			return ret;
 	}

 	return pmbus_do_probe(client, id, info);
 }

 static const struct i2c_device_id max31785_id[] = {
 	{ "max31785", 0 },
 	{ "max31785a", 0 },
 	{ },
 };

 MODULE_DEVICE_TABLE(i2c, max31785_id);

 static const struct of_device_id max31785_of_match[] = {
 	{ .compatible = "maxim,max31785" },
 	{ .compatible = "maxim,max31785a" },
 	{ },
 };

 MODULE_DEVICE_TABLE(of, max31785_of_match);

 static struct i2c_driver max31785_driver = {
 	.driver = {
 		.name = "max31785",
 		.of_match_table = max31785_of_match,
 	},
 	.probe = max31785_probe,
 	.remove = pmbus_do_remove,
 	.id_table = max31785_id,
 };

 module_i2c_driver(max31785_driver);

 MODULE_AUTHOR("Andrew Jeffery <andrew@aj.id.au>");
 MODULE_DESCRIPTION("PMBus driver for the Maxim MAX31785");
 MODULE_LICENSE("GPL");
	/*
	* Copyright (C) 2017 IBM Corp.
	*
	* This program is free software; you can redistribute it and/or modify
	* it under the terms of the GNU General Public License as published by
	* the Free Software Foundation; either version 2 of the License, or
	* (at your option) any later version.
	*/

	#include <linux/kernel.h>
	#include <linux/module.h>
	#include <linux/init.h>
	#include <linux/err.h>
	#include <linux/i2c.h>
	#include "pmbus.h"

	enum max31785_regs {
	MFR_REVISION = 0x9b,
	MFR_FAN_CONFIG = 0xf1,
	};

	#define MAX31785 0x3030
	#define MAX31785A 0x3040

	#define MFR_FAN_CONFIG_DUAL_TACH BIT(12)

	#define MAX31785_NR_PAGES 23
	#define MAX31785_NR_FAN_PAGES 6

	static int max31785_read_byte_data(struct i2c_client *client, int page,
	int reg)
	{
	if (page < MAX31785_NR_PAGES)
	return -ENODATA;

	switch (reg) {
	case PMBUS_VOUT_MODE:
	return -ENOTSUPP;
	case PMBUS_FAN_CONFIG_12:
	return pmbus_read_byte_data(client, page - MAX31785_NR_PAGES,
	reg);
	}

	return -ENODATA;
	}

	static int max31785_write_byte(struct i2c_client *client, int page, u8 value)
	{
	if (page < MAX31785_NR_PAGES)
	return -ENODATA;

	return -ENOTSUPP;
	}

	static int max31785_read_long_data(struct i2c_client *client, int page,
	int reg, u32 *data)
	{
	unsigned char cmdbuf[1];
	unsigned char rspbuf[4];
	int rc;

	struct i2c_msg msg[2] = {
	{
	.addr = client->addr,
	.flags = 0,
	.len = sizeof(cmdbuf),
	.buf = cmdbuf,
	},
	{
	.addr = client->addr,
	.flags = I2C_M_RD,
	.len = sizeof(rspbuf),
	.buf = rspbuf,
	},
	};

	cmdbuf[0] = reg;

	rc = pmbus_set_page(client, page);
	if (rc < 0)
	return rc;

	rc = i2c_transfer(client->adapter, msg, ARRAY_SIZE(msg));
	if (rc < 0)
	return rc;

	data = (rspbuf[0] << (0 8)) \| (rspbuf[1] << (1 * 8)) \|
	(rspbuf[2] << (2 * 8)) \| (rspbuf[3] << (3 * 8));

	return rc;
	}

	static int max31785_get_pwm(struct i2c_client *client, int page)
	{
	int rv;

	rv = pmbus_get_fan_rate_device(client, page, 0, percent);
	if (rv < 0)
	return rv;
	else if (rv >= 0x8000)
	return 0;
	else if (rv >= 0x2711)
	return 0x2710;

	return rv;
	}

	static int max31785_get_pwm_mode(struct i2c_client *client, int page)
	{
	int config;
	int command;

	config = pmbus_read_byte_data(client, page, PMBUS_FAN_CONFIG_12);
	if (config < 0)
	return config;

	command = pmbus_read_word_data(client, page, PMBUS_FAN_COMMAND_1);
	if (command < 0)
	return command;

	if (config & PB_FAN_1_RPM)
	return (command >= 0x8000) ? 3 : 2;

	if (command >= 0x8000)
	return 3;
	else if (command >= 0x2711)
	return 0;

	return 1;
	}

	static int max31785_read_word_data(struct i2c_client *client, int page,
	int reg)
	{
	u32 val;
	int rv;

	switch (reg) {
	case PMBUS_READ_FAN_SPEED_1:
	if (page < MAX31785_NR_PAGES)
	return -ENODATA;

	rv = max31785_read_long_data(client, page - MAX31785_NR_PAGES,
	reg, &val);
	if (rv < 0)
	return rv;

	rv = (val >> 16) & 0xffff;
	break;
	case PMBUS_FAN_COMMAND_1:
	/*
	* PMBUS_FAN_COMMAND_x is probed to judge whether or not to
	* expose fan control registers.
	*
	* Don't expose fan_target attribute for virtual pages.
	*/
	rv = (page >= MAX31785_NR_PAGES) ? -ENOTSUPP : -ENODATA;
	break;
	case PMBUS_VIRT_PWM_1:
	rv = max31785_get_pwm(client, page);
	break;
	case PMBUS_VIRT_PWM_ENABLE_1:
	rv = max31785_get_pwm_mode(client, page);
	break;
	default:
	rv = -ENODATA;
	break;
	}

	return rv;
	}

	static inline u32 max31785_scale_pwm(u32 sensor_val)
	{
	/*
	* The datasheet describes the accepted value range for manual PWM as
	* [0, 0x2710], while the hwmon pwmX sysfs interface accepts values in
	* [0, 255]. The MAX31785 uses DIRECT mode to scale the FAN_COMMAND
	* registers and in PWM mode the coefficients are m=1, b=0, R=2. The
	* important observation here is that 0x2710 == 10000 == 100 * 100.
	*
	* R=2 (== 10^2 == 100) accounts for scaling the value provided at the
	* sysfs interface into the required hardware resolution, but it does
	* not yet yield a value that we can write to the device (this initial
	* scaling is handled by pmbus_data2reg()). Multiplying by 100 below
	* translates the parameter value into the percentage units required by
	* PMBus, and then we scale back by 255 as required by the hwmon pwmX
	* interface to yield the percentage value at the appropriate
	* resolution for hardware.
	*/
	return (sensor_val * 100) / 255;
	}

	static int max31785_pwm_enable(struct i2c_client *client, int page,
	u16 word)
	{
	int config = 0;
	int rate;

	switch (word) {
	case 0:
	rate = 0x7fff;
	break;
	case 1:
	rate = pmbus_get_fan_rate_cached(client, page, 0, percent);
	if (rate < 0)
	return rate;
	rate = max31785_scale_pwm(rate);
	break;
	case 2:
	config = PB_FAN_1_RPM;
	rate = pmbus_get_fan_rate_cached(client, page, 0, rpm);
	if (rate < 0)
	return rate;
	break;
	case 3:
	rate = 0xffff;
	break;
	default:
	return -EINVAL;
	}

	return pmbus_update_fan(client, page, 0, config, PB_FAN_1_RPM, rate);
	}

	static int max31785_write_word_data(struct i2c_client *client, int page,
	int reg, u16 word)
	{
	switch (reg) {
	case PMBUS_VIRT_PWM_1:
	return pmbus_update_fan(client, page, 0, 0, PB_FAN_1_RPM,
	max31785_scale_pwm(word));
	case PMBUS_VIRT_PWM_ENABLE_1:
	return max31785_pwm_enable(client, page, word);
	default:
	break;
	}

	return -ENODATA;
	}

	#define MAX31785_FAN_FUNCS \
	(PMBUS_HAVE_FAN12 \| PMBUS_HAVE_STATUS_FAN12 \| PMBUS_HAVE_PWM12)

	#define MAX31785_TEMP_FUNCS \
	(PMBUS_HAVE_TEMP \| PMBUS_HAVE_STATUS_TEMP)

	#define MAX31785_VOUT_FUNCS \
	(PMBUS_HAVE_VOUT \| PMBUS_HAVE_STATUS_VOUT)

	#define MAX37185_NUM_FAN_PAGES 6

	static const struct pmbus_driver_info max31785_info = {
	.pages = MAX31785_NR_PAGES,

	.write_word_data = max31785_write_word_data,
	.read_byte_data = max31785_read_byte_data,
	.read_word_data = max31785_read_word_data,
	.write_byte = max31785_write_byte,

	/* RPM */
	.format[PSC_FAN] = direct,
	.m[PSC_FAN] = 1,
	.b[PSC_FAN] = 0,
	.R[PSC_FAN] = 0,
	/* PWM */
	.format[PSC_PWM] = direct,
	.m[PSC_PWM] = 1,
	.b[PSC_PWM] = 0,
	.R[PSC_PWM] = 2,
	.func[0] = MAX31785_FAN_FUNCS,
	.func[1] = MAX31785_FAN_FUNCS,
	.func[2] = MAX31785_FAN_FUNCS,
	.func[3] = MAX31785_FAN_FUNCS,
	.func[4] = MAX31785_FAN_FUNCS,
	.func[5] = MAX31785_FAN_FUNCS,

	.format[PSC_TEMPERATURE] = direct,
	.m[PSC_TEMPERATURE] = 1,
	.b[PSC_TEMPERATURE] = 0,
	.R[PSC_TEMPERATURE] = 2,
	.func[6] = MAX31785_TEMP_FUNCS,
	.func[7] = MAX31785_TEMP_FUNCS,
	.func[8] = MAX31785_TEMP_FUNCS,
	.func[9] = MAX31785_TEMP_FUNCS,
	.func[10] = MAX31785_TEMP_FUNCS,
	.func[11] = MAX31785_TEMP_FUNCS,
	.func[12] = MAX31785_TEMP_FUNCS,
	.func[13] = MAX31785_TEMP_FUNCS,
	.func[14] = MAX31785_TEMP_FUNCS,
	.func[15] = MAX31785_TEMP_FUNCS,
	.func[16] = MAX31785_TEMP_FUNCS,

	.format[PSC_VOLTAGE_OUT] = direct,
	.m[PSC_VOLTAGE_OUT] = 1,
	.b[PSC_VOLTAGE_OUT] = 0,
	.R[PSC_VOLTAGE_OUT] = 0,
	.func[17] = MAX31785_VOUT_FUNCS,
	.func[18] = MAX31785_VOUT_FUNCS,
	.func[19] = MAX31785_VOUT_FUNCS,
	.func[20] = MAX31785_VOUT_FUNCS,
	.func[21] = MAX31785_VOUT_FUNCS,
	.func[22] = MAX31785_VOUT_FUNCS,
	};

	static int max31785_configure_dual_tach(struct i2c_client *client,
	struct pmbus_driver_info *info)
	{
	int ret;
	int i;

	for (i = 0; i < MAX31785_NR_FAN_PAGES; i++) {
	ret = i2c_smbus_write_byte_data(client, PMBUS_PAGE, i);
	if (ret < 0)
	return ret;

	ret = i2c_smbus_read_word_data(client, MFR_FAN_CONFIG);
	if (ret < 0)
	return ret;

	if (ret & MFR_FAN_CONFIG_DUAL_TACH) {
	int virtual = MAX31785_NR_PAGES + i;

	info->pages = virtual + 1;
	info->func[virtual] \|= PMBUS_HAVE_FAN12;
	info->func[virtual] \|= PMBUS_PAGE_VIRTUAL;
	}
	}

	return 0;
	}

	static int max31785_probe(struct i2c_client *client,
	const struct i2c_device_id *id)
	{
	struct device *dev = &client->dev;
	struct pmbus_driver_info *info;
	bool dual_tach = false;
	s64 ret;

	if (!i2c_check_functionality(client->adapter,
	I2C_FUNC_SMBUS_BYTE_DATA \|
	I2C_FUNC_SMBUS_WORD_DATA))
	return -ENODEV;

	info = devm_kzalloc(dev, sizeof(struct pmbus_driver_info), GFP_KERNEL);
	if (!info)
	return -ENOMEM;

	*info = max31785_info;

	ret = i2c_smbus_write_byte_data(client, PMBUS_PAGE, 255);
	if (ret < 0)
	return ret;

	ret = i2c_smbus_read_word_data(client, MFR_REVISION);
	if (ret < 0)
	return ret;

	if (ret == MAX31785A) {
	dual_tach = true;
	} else if (ret == MAX31785) {
	if (!strcmp("max31785a", id->name))
	dev_warn(dev, "Expected max3175a, found max31785: cannot provide secondary tachometer readings\n");
	} else {
	return -ENODEV;
	}

	if (dual_tach) {
	ret = max31785_configure_dual_tach(client, info);
	if (ret < 0)
	return ret;
	}

	return pmbus_do_probe(client, id, info);
	}

	static const struct i2c_device_id max31785_id[] = {
	{ "max31785", 0 },
	{ "max31785a", 0 },
	{ },
	};

	MODULE_DEVICE_TABLE(i2c, max31785_id);

	static const struct of_device_id max31785_of_match[] = {
	{ .compatible = "maxim,max31785" },
	{ .compatible = "maxim,max31785a" },
	{ },
	};

	MODULE_DEVICE_TABLE(of, max31785_of_match);

	static struct i2c_driver max31785_driver = {
	.driver = {
	.name = "max31785",
	.of_match_table = max31785_of_match,
	},
	.probe = max31785_probe,
	.remove = pmbus_do_remove,
	.id_table = max31785_id,
	};

	module_i2c_driver(max31785_driver);

	MODULE_AUTHOR("Andrew Jeffery <andrew@aj.id.au>");
	MODULE_DESCRIPTION("PMBus driver for the Maxim MAX31785");
	MODULE_LICENSE("GPL");