linux/drivers/hwmon/pmbus/max31785.c

// SPDX-License-Identifier: GPL-2.0-or-later
/*
 * Copyright (C) 2017 IBM Corp.
 */

#include <linux/delay.h>
#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 MAX31785B			0x3061

#define MFR_FAN_CONFIG_DUAL_TACH	BIT(12)

#define MAX31785_NR_PAGES		23
#define MAX31785_NR_FAN_PAGES		6
#define MAX31785_WAIT_DELAY_US		250

struct max31785_data {
	ktime_t access;			/* Chip access time */
	struct pmbus_driver_info info;
};

#define to_max31785_data(x)  container_of(x, struct max31785_data, info)

/*
 * MAX31785 Driver Workaround
 *
 * The MAX31785 fan controller occasionally exhibits communication issues.
 * These issues are not indicated by the device itself, except for occasional
 * NACK responses during master transactions. No error bits are set in STATUS_BYTE.
 *
 * To address this, we introduce a delay of 250us between consecutive accesses
 * to the fan controller. This delay helps mitigate communication problems by
 * allowing sufficient time between accesses.
 */
static inline void max31785_wait(const struct max31785_data *data)
{
	s64 delta = ktime_us_delta(ktime_get(), data->access);

	if (delta < MAX31785_WAIT_DELAY_US)
		usleep_range(MAX31785_WAIT_DELAY_US - delta,
			     MAX31785_WAIT_DELAY_US);
}

static int max31785_i2c_write_byte_data(struct i2c_client *client,
					struct max31785_data *driver_data,
					int command, u16 data)
{
	int rc;

	max31785_wait(driver_data);
	rc = i2c_smbus_write_byte_data(client, command, data);
	driver_data->access = ktime_get();
	return rc;
}

static int max31785_i2c_read_word_data(struct i2c_client *client,
				       struct max31785_data *driver_data,
				       int command)
{
	int rc;

	max31785_wait(driver_data);
	rc = i2c_smbus_read_word_data(client, command);
	driver_data->access = ktime_get();
	return rc;
}

static int _max31785_read_byte_data(struct i2c_client *client,
				    struct max31785_data *driver_data,
				    int page, int command)
{
	int rc;

	max31785_wait(driver_data);
	rc = pmbus_read_byte_data(client, page, command);
	driver_data->access = ktime_get();
	return rc;
}

static int _max31785_write_byte_data(struct i2c_client *client,
				     struct max31785_data *driver_data,
				     int page, int command, u16 data)
{
	int rc;

	max31785_wait(driver_data);
	rc = pmbus_write_byte_data(client, page, command, data);
	driver_data->access = ktime_get();
	return rc;
}

static int _max31785_read_word_data(struct i2c_client *client,
				    struct max31785_data *driver_data,
				    int page, int phase, int command)
{
	int rc;

	max31785_wait(driver_data);
	rc = pmbus_read_word_data(client, page, phase, command);
	driver_data->access = ktime_get();
	return rc;
}

static int _max31785_write_word_data(struct i2c_client *client,
				     struct max31785_data *driver_data,
				     int page, int command, u16 data)
{
	int rc;

	max31785_wait(driver_data);
	rc = pmbus_write_word_data(client, page, command, data);
	driver_data->access = ktime_get();
	return rc;
}

static int max31785_read_byte_data(struct i2c_client *client, int page, int reg)
{
	const struct pmbus_driver_info *info = pmbus_get_driver_info(client);
	struct max31785_data *driver_data = to_max31785_data(info);

	switch (reg) {
	case PMBUS_VOUT_MODE:
		return -ENOTSUPP;
	case PMBUS_FAN_CONFIG_12:
		return _max31785_read_byte_data(client, driver_data,
						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, 0xff);
	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,
				 struct max31785_data *driver_data, int page)
{
	int config;
	int command;

	config = _max31785_read_byte_data(client, driver_data, page,
					  PMBUS_FAN_CONFIG_12);
	if (config < 0)
		return config;

	command = _max31785_read_word_data(client, driver_data, page, 0xff,
					   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 phase, int reg)
{
	const struct pmbus_driver_info *info = pmbus_get_driver_info(client);
	struct max31785_data *driver_data = to_max31785_data(info);
	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, driver_data, 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_update_fan(struct i2c_client *client,
			       struct max31785_data *driver_data, int page,
			       u8 config, u8 mask, u16 command)
{
	int from, rv;
	u8 to;

	from = _max31785_read_byte_data(client, driver_data, page,
					PMBUS_FAN_CONFIG_12);
	if (from < 0)
		return from;

	to = (from & ~mask) | (config & mask);

	if (to != from) {
		rv = _max31785_write_byte_data(client, driver_data, page,
					       PMBUS_FAN_CONFIG_12, to);
		if (rv < 0)
			return rv;
	}

	rv = _max31785_write_word_data(client, driver_data, page,
				       PMBUS_FAN_COMMAND_1, command);

	return rv;
}

static int max31785_pwm_enable(struct i2c_client *client,
			       struct max31785_data *driver_data, 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 max31785_update_fan(client, driver_data, page, config,
				   PB_FAN_1_RPM, rate);
}

static int max31785_write_word_data(struct i2c_client *client, int page,
				    int reg, u16 word)
{
	const struct pmbus_driver_info *info = pmbus_get_driver_info(client);
	struct max31785_data *driver_data = to_max31785_data(info);

	switch (reg) {
	case PMBUS_VIRT_PWM_1:
		return max31785_update_fan(client, driver_data, page, 0,
					   PB_FAN_1_RPM,
					   max31785_scale_pwm(word));
	case PMBUS_VIRT_PWM_ENABLE_1:
		return max31785_pwm_enable(client, driver_data, 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)

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;
	struct max31785_data *driver_data = to_max31785_data(info);

	for (i = 0; i < MAX31785_NR_FAN_PAGES; i++) {
		ret = max31785_i2c_write_byte_data(client, driver_data,
						   PMBUS_PAGE, i);
		if (ret < 0)
			return ret;

		ret = max31785_i2c_read_word_data(client, driver_data,
						  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)
{
	struct device *dev = &client->dev;
	struct pmbus_driver_info *info;
	struct max31785_data *driver_data;
	bool dual_tach = false;
	int ret;

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

	driver_data = devm_kzalloc(dev, sizeof(struct max31785_data), GFP_KERNEL);
	if (!driver_data)
		return -ENOMEM;

	info = &driver_data->info;
	driver_data->access = ktime_get();
	*info = max31785_info;

	ret = max31785_i2c_write_byte_data(client, driver_data,
					   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 || ret == MAX31785B) {
		dual_tach = true;
	} else if (ret == MAX31785) {
		if (!strcmp("max31785a", client->name) ||
		    !strcmp("max31785b", client->name))
			dev_warn(dev, "Expected max31785a/b, found max31785: cannot provide secondary tachometer readings\n");
	} else {
		dev_err(dev, "Unrecognized MAX31785 revision: %x\n", ret);
		return -ENODEV;
	}

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

	return pmbus_do_probe(client, info);
}

static const struct i2c_device_id max31785_id[] = {
	{ "max31785" },
	{ "max31785a" },
	{ "max31785b" },
	{ },
};

MODULE_DEVICE_TABLE(i2c, max31785_id);

static const struct of_device_id max31785_of_match[] = {
	{ .compatible = "maxim,max31785" },
	{ .compatible = "maxim,max31785a" },
	{ .compatible = "maxim,max31785b" },
	{ },
};

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,
	.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");
MODULE_IMPORT_NS(PMBUS);