chipcap2.c

// SPDX-License-Identifier: GPL-2.0+
/*
 * cc2.c - Support for the Amphenol ChipCap 2 relative humidity, temperature sensor
 *
 * Part numbers supported:
 * CC2D23, CC2D23S, CC2D25, CC2D25S, CC2D33, CC2D33S, CC2D35, CC2D35S
 *
 * Author: Javier Carrasco <javier.carrasco.cruz@gmail.com>
 *
 * Datasheet and application notes:
 * https://www.amphenol-sensors.com/en/telaire/humidity/527-humidity-sensors/3095-chipcap-2
 */

#include <linux/bitfield.h>
#include <linux/bits.h>
#include <linux/completion.h>
#include <linux/delay.h>
#include <linux/hwmon.h>
#include <linux/i2c.h>
#include <linux/interrupt.h>
#include <linux/irq.h>
#include <linux/module.h>
#include <linux/regulator/consumer.h>

#define CC2_START_CM			0xA0
#define CC2_START_NOM			0x80
#define CC2_R_ALARM_H_ON		0x18
#define CC2_R_ALARM_H_OFF		0x19
#define CC2_R_ALARM_L_ON		0x1A
#define CC2_R_ALARM_L_OFF		0x1B
#define CC2_RW_OFFSET			0x40
#define CC2_W_ALARM_H_ON		(CC2_R_ALARM_H_ON + CC2_RW_OFFSET)
#define CC2_W_ALARM_H_OFF		(CC2_R_ALARM_H_OFF + CC2_RW_OFFSET)
#define CC2_W_ALARM_L_ON		(CC2_R_ALARM_L_ON + CC2_RW_OFFSET)
#define CC2_W_ALARM_L_OFF		(CC2_R_ALARM_L_OFF + CC2_RW_OFFSET)

#define CC2_STATUS_FIELD		GENMASK(7, 6)
#define CC2_STATUS_VALID_DATA		0x00
#define CC2_STATUS_STALE_DATA		0x01
#define CC2_STATUS_CMD_MODE		0x02

#define CC2_RESPONSE_FIELD		GENMASK(1, 0)
#define CC2_RESPONSE_BUSY		0x00
#define CC2_RESPONSE_ACK		0x01
#define CC2_RESPONSE_NACK		0x02

#define CC2_ERR_CORR_EEPROM		BIT(2)
#define CC2_ERR_UNCORR_EEPROM		BIT(3)
#define CC2_ERR_RAM_PARITY		BIT(4)
#define CC2_ERR_CONFIG_LOAD		BIT(5)

#define CC2_EEPROM_SIZE			10
#define CC2_EEPROM_DATA_LEN		3
#define CC2_MEASUREMENT_DATA_LEN	4

#define CC2_RH_DATA_FIELD		GENMASK(13, 0)

/* ensure clean off -> on transitions */
#define CC2_POWER_CYCLE_MS		80

#define CC2_STARTUP_TO_DATA_MS		55
#define CC2_RESP_START_CM_US		100
#define CC2_RESP_EEPROM_R_US		100
#define CC2_RESP_EEPROM_W_MS		12
#define CC2_STARTUP_TIME_US		1250

#define CC2_RH_MAX			(100 * 1000U)

#define CC2_CM_RETRIES			5

struct cc2_rh_alarm_info {
	bool low_alarm;
	bool high_alarm;
	bool low_alarm_visible;
	bool high_alarm_visible;
};

struct cc2_data {
	struct cc2_rh_alarm_info rh_alarm;
	struct completion complete;
	struct device *hwmon;
	struct i2c_client *client;
	struct mutex dev_access_lock; /* device access lock */
	struct regulator *regulator;
	const char *name;
	int irq_ready;
	int irq_low;
	int irq_high;
	bool process_irqs;
};

enum cc2_chan_addr {
	CC2_CHAN_TEMP = 0,
	CC2_CHAN_HUMIDITY,
};

/* %RH as a per cent mille from a register value */
static long cc2_rh_convert(u16 data)
{
	unsigned long tmp = (data & CC2_RH_DATA_FIELD) * CC2_RH_MAX;

	return tmp / ((1 << 14) - 1);
}

/* convert %RH to a register value */
static u16 cc2_rh_to_reg(long data)
{
	return data * ((1 << 14) - 1) / CC2_RH_MAX;
}

/* temperature in milli degrees celsius from a register value */
static long cc2_temp_convert(u16 data)
{
	unsigned long tmp = ((data >> 2) * 165 * 1000U) / ((1 << 14) - 1);

	return tmp - 40 * 1000U;
}

static int cc2_enable(struct cc2_data *data)
{
	int ret;

	/* exclusive regulator, check in case a disable failed */
	if (regulator_is_enabled(data->regulator))
		return 0;

	/* clear any pending completion */
	try_wait_for_completion(&data->complete);

	ret = regulator_enable(data->regulator);
	if (ret < 0)
		return ret;

	usleep_range(CC2_STARTUP_TIME_US, CC2_STARTUP_TIME_US + 125);

	data->process_irqs = true;

	return 0;
}

static void cc2_disable(struct cc2_data *data)
{
	int err;

	/* ignore alarms triggered by voltage toggling when powering up */
	data->process_irqs = false;

	/* exclusive regulator, check in case an enable failed */
	if (regulator_is_enabled(data->regulator)) {
		err = regulator_disable(data->regulator);
		if (err)
			dev_dbg(&data->client->dev, "Failed to disable device");
	}
}

static int cc2_cmd_response_diagnostic(struct device *dev, u8 status)
{
	int resp;

	if (FIELD_GET(CC2_STATUS_FIELD, status) != CC2_STATUS_CMD_MODE) {
		dev_dbg(dev, "Command sent out of command window\n");
		return -ETIMEDOUT;
	}

	resp = FIELD_GET(CC2_RESPONSE_FIELD, status);
	switch (resp) {
	case CC2_RESPONSE_ACK:
		return 0;
	case CC2_RESPONSE_BUSY:
		return -EBUSY;
	case CC2_RESPONSE_NACK:
		if (resp & CC2_ERR_CORR_EEPROM)
			dev_dbg(dev, "Command failed: corrected EEPROM\n");
		if (resp & CC2_ERR_UNCORR_EEPROM)
			dev_dbg(dev, "Command failed: uncorrected EEPROM\n");
		if (resp & CC2_ERR_RAM_PARITY)
			dev_dbg(dev, "Command failed: RAM parity\n");
		if (resp & CC2_ERR_RAM_PARITY)
			dev_dbg(dev, "Command failed: configuration error\n");
		return -ENODATA;
	default:
		dev_dbg(dev, "Unknown command reply\n");
		return -EINVAL;
	}
}

static int cc2_read_command_status(struct i2c_client *client)
{
	u8 status;
	int ret;

	ret = i2c_master_recv(client, &status, 1);
	if (ret != 1) {
		ret = ret < 0 ? ret : -EIO;
		return ret;
	}

	return cc2_cmd_response_diagnostic(&client->dev, status);
}

/*
 * The command mode is only accessible after sending the START_CM command in the
 * first 10 ms after power-up. Only in case the command window is missed,
 * CC2_CM_RETRIES retries are attempted before giving up and returning an error.
 */
static int cc2_command_mode_start(struct cc2_data *data)
{
	unsigned long timeout;
	int i, ret;

	for (i = 0; i < CC2_CM_RETRIES; i++) {
		ret = cc2_enable(data);
		if (ret < 0)
			return ret;

		ret = i2c_smbus_write_word_data(data->client, CC2_START_CM, 0);
		if (ret < 0)
			return ret;

		if (data->irq_ready > 0) {
			timeout = usecs_to_jiffies(2 * CC2_RESP_START_CM_US);
			ret = wait_for_completion_timeout(&data->complete,
							  timeout);
			if (!ret)
				return -ETIMEDOUT;
		} else {
			usleep_range(CC2_RESP_START_CM_US,
				     2 * CC2_RESP_START_CM_US);
		}
		ret = cc2_read_command_status(data->client);
		if (ret != -ETIMEDOUT || i == CC2_CM_RETRIES)
			break;

		/* command window missed, prepare for a retry */
		cc2_disable(data);
		msleep(CC2_POWER_CYCLE_MS);
	}

	return ret;
}

/* Sending a Start_NOM command finishes the command mode immediately with no
 * reply and the device enters normal operation mode
 */
static int cc2_command_mode_finish(struct cc2_data *data)
{
	int ret;

	ret = i2c_smbus_write_word_data(data->client, CC2_START_NOM, 0);
	if (ret < 0)
		return ret;

	return 0;
}

static int cc2_write_reg(struct cc2_data *data, u8 reg, u16 val)
{
	unsigned long timeout;
	int ret;

	ret = cc2_command_mode_start(data);
	if (ret < 0)
		goto disable;

	cpu_to_be16s(&val);
	ret = i2c_smbus_write_word_data(data->client, reg, val);
	if (ret < 0)
		goto disable;

	if (data->irq_ready > 0) {
		timeout = msecs_to_jiffies(2 * CC2_RESP_EEPROM_W_MS);
		ret = wait_for_completion_timeout(&data->complete, timeout);
		if (!ret) {
			ret = -ETIMEDOUT;
			goto disable;
		}
	} else {
		msleep(CC2_RESP_EEPROM_W_MS);
	}

	ret = cc2_read_command_status(data->client);

disable:
	cc2_disable(data);

	return ret;
}

static int cc2_read_reg(struct cc2_data *data, u8 reg, u16 *val)
{
	u8 buf[CC2_EEPROM_DATA_LEN];
	unsigned long timeout;
	int ret;

	ret = cc2_command_mode_start(data);
	if (ret < 0)
		return ret;

	ret = i2c_smbus_write_word_data(data->client, reg, 0);
	if (ret < 0)
		return ret;

	if (data->irq_ready > 0) {
		timeout = usecs_to_jiffies(2 * CC2_RESP_EEPROM_R_US);
		ret = wait_for_completion_timeout(&data->complete, timeout);
		if (!ret)
			return -ETIMEDOUT;

	} else {
		usleep_range(CC2_RESP_EEPROM_R_US, CC2_RESP_EEPROM_R_US + 10);
	}
	ret = i2c_master_recv(data->client, buf, CC2_EEPROM_DATA_LEN);
	if (ret != CC2_EEPROM_DATA_LEN)
		return ret < 0 ? ret : -EIO;

	*val = be16_to_cpup((__be16 *)&buf[1]);

	return cc2_read_command_status(data->client);
}

static int cc2_get_reg_val(struct cc2_data *data, u8 reg, long *val)
{
	u16 reg_val;
	int ret;

	ret = cc2_read_reg(data, reg, &reg_val);
	if (!ret)
		*val = cc2_rh_convert(reg_val);

	cc2_disable(data);

	return ret;
}

static int cc2_data_fetch(struct i2c_client *client,
			  enum hwmon_sensor_types type, long *val)
{
	u8 data[CC2_MEASUREMENT_DATA_LEN];
	u8 status;
	int ret;

	ret = i2c_master_recv(client, data, CC2_MEASUREMENT_DATA_LEN);
	if (ret != CC2_MEASUREMENT_DATA_LEN) {
		ret = ret < 0 ? ret : -EIO;
		return ret;
	}
	status = FIELD_GET(CC2_STATUS_FIELD, data[0]);
	if (status == CC2_STATUS_STALE_DATA)
		return -EBUSY;

	if (status != CC2_STATUS_VALID_DATA)
		return -EIO;

	switch (type) {
	case hwmon_humidity:
		*val = cc2_rh_convert(be16_to_cpup((__be16 *)&data[0]));
		break;
	case hwmon_temp:
		*val = cc2_temp_convert(be16_to_cpup((__be16 *)&data[2]));
		break;
	default:
		return -EINVAL;
	}

	return 0;
}

static int cc2_read_measurement(struct cc2_data *data,
				enum hwmon_sensor_types type, long *val)
{
	unsigned long timeout;
	int ret;

	if (data->irq_ready > 0) {
		timeout = msecs_to_jiffies(CC2_STARTUP_TO_DATA_MS * 2);
		ret = wait_for_completion_timeout(&data->complete, timeout);
		if (!ret)
			return -ETIMEDOUT;

	} else {
		msleep(CC2_STARTUP_TO_DATA_MS);
	}

	ret = cc2_data_fetch(data->client, type, val);

	return ret;
}

/*
 * A measurement requires enabling the device, waiting for the automatic
 * measurement to finish, reading the measurement data and disabling the device
 * again.
 */
static int cc2_measurement(struct cc2_data *data, enum hwmon_sensor_types type,
			   long *val)
{
	int ret;

	ret = cc2_enable(data);
	if (ret)
		return ret;

	ret = cc2_read_measurement(data, type, val);

	cc2_disable(data);

	return ret;
}

/*
 * In order to check alarm status, the corresponding ALARM_OFF (hysteresis)
 * register must be read and a new measurement must be carried out to trigger
 * the alarm signals. Given that the device carries out a measurement after
 * exiting the command mode, there is no need to force two power-up sequences.
 * Instead, a NOM command is sent and the device is disabled after the
 * measurement is read.
 */
static int cc2_read_hyst_and_measure(struct cc2_data *data, u8 reg,
				     long *hyst, long *measurement)
{
	u16 reg_val;
	int ret;

	ret = cc2_read_reg(data, reg, &reg_val);
	if (ret)
		goto disable;

	*hyst = cc2_rh_convert(reg_val);

	ret = cc2_command_mode_finish(data);
	if (ret)
		goto disable;

	ret = cc2_read_measurement(data, hwmon_humidity, measurement);

disable:
	cc2_disable(data);

	return ret;
}

static umode_t cc2_is_visible(const void *data, enum hwmon_sensor_types type,
			      u32 attr, int channel)
{
	const struct cc2_data *cc2 = data;

	switch (type) {
	case hwmon_humidity:
		switch (attr) {
		case hwmon_humidity_input:
			return 0444;
		case hwmon_humidity_min_alarm:
			return cc2->rh_alarm.low_alarm_visible ? 0444 : 0;
		case hwmon_humidity_max_alarm:
			return cc2->rh_alarm.high_alarm_visible ? 0444 : 0;
		case hwmon_humidity_min:
		case hwmon_humidity_min_hyst:
			return cc2->rh_alarm.low_alarm_visible ? 0644 : 0;
		case hwmon_humidity_max:
		case hwmon_humidity_max_hyst:
			return cc2->rh_alarm.high_alarm_visible ? 0644 : 0;
		default:
			return 0;
		}
	case hwmon_temp:
		switch (attr) {
		case hwmon_temp_input:
			return 0444;
		default:
			return 0;
		}
	default:
		break;
	}

	return 0;
}

static irqreturn_t cc2_ready_interrupt(int irq, void *data)
{
	struct cc2_data *cc2 = data;

	if (cc2->process_irqs)
		complete(&cc2->complete);

	return IRQ_HANDLED;
}

static irqreturn_t cc2_low_interrupt(int irq, void *data)
{
	struct cc2_data *cc2 = data;

	if (cc2->process_irqs) {
		hwmon_notify_event(cc2->hwmon, hwmon_humidity,
				   hwmon_humidity_min_alarm, CC2_CHAN_HUMIDITY);
		cc2->rh_alarm.low_alarm = true;
	}

	return IRQ_HANDLED;
}

static irqreturn_t cc2_high_interrupt(int irq, void *data)
{
	struct cc2_data *cc2 = data;

	if (cc2->process_irqs) {
		hwmon_notify_event(cc2->hwmon, hwmon_humidity,
				   hwmon_humidity_max_alarm, CC2_CHAN_HUMIDITY);
		cc2->rh_alarm.high_alarm = true;
	}

	return IRQ_HANDLED;
}

static int cc2_humidity_min_alarm_status(struct cc2_data *data, long *val)
{
	long measurement, min_hyst;
	int ret;

	ret = cc2_read_hyst_and_measure(data, CC2_R_ALARM_L_OFF, &min_hyst,
					&measurement);
	if (ret < 0)
		return ret;

	if (data->rh_alarm.low_alarm) {
		*val = (measurement < min_hyst) ? 1 : 0;
		data->rh_alarm.low_alarm = *val;
	} else {
		*val = 0;
	}

	return 0;
}

static int cc2_humidity_max_alarm_status(struct cc2_data *data, long *val)
{
	long measurement, max_hyst;
	int ret;

	ret = cc2_read_hyst_and_measure(data, CC2_R_ALARM_H_OFF, &max_hyst,
					&measurement);
	if (ret < 0)
		return ret;

	if (data->rh_alarm.high_alarm) {
		*val = (measurement > max_hyst) ? 1 : 0;
		data->rh_alarm.high_alarm = *val;
	} else {
		*val = 0;
	}

	return 0;
}

static int cc2_read(struct device *dev, enum hwmon_sensor_types type, u32 attr,
		    int channel, long *val)
{
	struct cc2_data *data = dev_get_drvdata(dev);
	int ret = 0;

	mutex_lock(&data->dev_access_lock);

	switch (type) {
	case hwmon_temp:
		ret = cc2_measurement(data, type, val);
		break;
	case hwmon_humidity:
		switch (attr) {
		case hwmon_humidity_input:
			ret = cc2_measurement(data, type, val);
			break;
		case hwmon_humidity_min:
			ret = cc2_get_reg_val(data, CC2_R_ALARM_L_ON, val);
			break;
		case hwmon_humidity_min_hyst:
			ret = cc2_get_reg_val(data, CC2_R_ALARM_L_OFF, val);
			break;
		case hwmon_humidity_max:
			ret = cc2_get_reg_val(data, CC2_R_ALARM_H_ON, val);
			break;
		case hwmon_humidity_max_hyst:
			ret = cc2_get_reg_val(data, CC2_R_ALARM_H_OFF, val);
			break;
		case hwmon_humidity_min_alarm:
			ret = cc2_humidity_min_alarm_status(data, val);
			break;
		case hwmon_humidity_max_alarm:
			ret = cc2_humidity_max_alarm_status(data, val);
			break;
		default:
			ret = -EOPNOTSUPP;
		}
		break;
	default:
		ret = -EOPNOTSUPP;
	}

	mutex_unlock(&data->dev_access_lock);

	return ret;
}

static int cc2_write(struct device *dev, enum hwmon_sensor_types type, u32 attr,
		     int channel, long val)
{
	struct cc2_data *data = dev_get_drvdata(dev);
	int ret;
	u16 arg;
	u8 cmd;

	if (type != hwmon_humidity)
		return -EOPNOTSUPP;

	if (val < 0 || val > CC2_RH_MAX)
		return -EINVAL;

	mutex_lock(&data->dev_access_lock);

	switch (attr) {
	case hwmon_humidity_min:
		cmd = CC2_W_ALARM_L_ON;
		arg = cc2_rh_to_reg(val);
		ret = cc2_write_reg(data, cmd, arg);
		break;

	case hwmon_humidity_min_hyst:
		cmd = CC2_W_ALARM_L_OFF;
		arg = cc2_rh_to_reg(val);
		ret = cc2_write_reg(data, cmd, arg);
		break;

	case hwmon_humidity_max:
		cmd = CC2_W_ALARM_H_ON;
		arg = cc2_rh_to_reg(val);
		ret = cc2_write_reg(data, cmd, arg);
		break;

	case hwmon_humidity_max_hyst:
		cmd = CC2_W_ALARM_H_OFF;
		arg = cc2_rh_to_reg(val);
		ret = cc2_write_reg(data, cmd, arg);
		break;

	default:
		ret = -EOPNOTSUPP;
		break;
	}

	mutex_unlock(&data->dev_access_lock);

	return ret;
}

static int cc2_request_ready_irq(struct cc2_data *data, struct device *dev)
{
	int ret = 0;

	data->irq_ready = fwnode_irq_get_byname(dev_fwnode(dev), "ready");
	if (data->irq_ready > 0) {
		init_completion(&data->complete);
		ret = devm_request_threaded_irq(dev, data->irq_ready, NULL,
						cc2_ready_interrupt,
						IRQF_ONESHOT |
						IRQF_TRIGGER_RISING,
						dev_name(dev), data);
	}

	return ret;
}

static int cc2_request_alarm_irqs(struct cc2_data *data, struct device *dev)
{
	int ret = 0;

	data->irq_low = fwnode_irq_get_byname(dev_fwnode(dev), "low");
	if (data->irq_low > 0) {
		ret = devm_request_threaded_irq(dev, data->irq_low, NULL,
						cc2_low_interrupt,
						IRQF_ONESHOT |
						IRQF_TRIGGER_RISING,
						dev_name(dev), data);
		if (ret)
			return ret;

		data->rh_alarm.low_alarm_visible = true;
	}

	data->irq_high = fwnode_irq_get_byname(dev_fwnode(dev), "high");
	if (data->irq_high > 0) {
		ret = devm_request_threaded_irq(dev, data->irq_high, NULL,
						cc2_high_interrupt,
						IRQF_ONESHOT |
						IRQF_TRIGGER_RISING,
						dev_name(dev), data);
		if (ret)
			return ret;

		data->rh_alarm.high_alarm_visible = true;
	}

	return ret;
}

static const struct hwmon_channel_info *cc2_info[] = {
	HWMON_CHANNEL_INFO(temp, HWMON_T_INPUT),
	HWMON_CHANNEL_INFO(humidity, HWMON_H_INPUT | HWMON_H_MIN | HWMON_H_MAX |
			   HWMON_H_MIN_HYST | HWMON_H_MAX_HYST |
			   HWMON_H_MIN_ALARM | HWMON_H_MAX_ALARM),
	NULL
};

static const struct hwmon_ops cc2_hwmon_ops = {
	.is_visible = cc2_is_visible,
	.read = cc2_read,
	.write = cc2_write,
};

static const struct hwmon_chip_info cc2_chip_info = {
	.ops = &cc2_hwmon_ops,
	.info = cc2_info,
};

static int cc2_probe(struct i2c_client *client)
{
	struct cc2_data *data;
	struct device *dev = &client->dev;
	int ret;

	if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C))
		return -EOPNOTSUPP;

	data = devm_kzalloc(dev, sizeof(*data), GFP_KERNEL);
	if (!data)
		return -ENOMEM;

	i2c_set_clientdata(client, data);

	mutex_init(&data->dev_access_lock);

	data->client = client;

	data->regulator = devm_regulator_get_exclusive(dev, "vdd");
	if (IS_ERR(data->regulator)) {
		dev_err_probe(dev, PTR_ERR(data->regulator),
			      "Failed to get regulator\n");
		return PTR_ERR(data->regulator);
	}

	ret = cc2_request_ready_irq(data, dev);
	if (ret) {
		dev_err_probe(dev, ret, "Failed to request ready irq\n");
		return ret;
	}

	ret = cc2_request_alarm_irqs(data, dev);
	if (ret) {
		dev_err_probe(dev, ret, "Failed to request alarm irqs\n");
		goto disable;
	}

	data->hwmon = devm_hwmon_device_register_with_info(dev, client->name,
							   data, &cc2_chip_info,
							   NULL);
	if (IS_ERR(data->hwmon)) {
		dev_err_probe(dev, PTR_ERR(data->hwmon),
			      "Failed to register hwmon device\n");
		ret = PTR_ERR(data->hwmon);
	}

disable:
	cc2_disable(data);

	return ret;
}

static void cc2_remove(struct i2c_client *client)
{
	struct cc2_data *data = i2c_get_clientdata(client);

	cc2_disable(data);
}

static const struct i2c_device_id cc2_id[] = {
	{ "cc2d23" },
	{ "cc2d23s" },
	{ "cc2d25" },
	{ "cc2d25s" },
	{ "cc2d33" },
	{ "cc2d33s" },
	{ "cc2d35" },
	{ "cc2d35s" },
	{ }
};
MODULE_DEVICE_TABLE(i2c, cc2_id);

static const struct of_device_id cc2_of_match[] = {
	{ .compatible = "amphenol,cc2d23" },
	{ .compatible = "amphenol,cc2d23s" },
	{ .compatible = "amphenol,cc2d25" },
	{ .compatible = "amphenol,cc2d25s" },
	{ .compatible = "amphenol,cc2d33" },
	{ .compatible = "amphenol,cc2d33s" },
	{ .compatible = "amphenol,cc2d35" },
	{ .compatible = "amphenol,cc2d35s" },
	{ },
};
MODULE_DEVICE_TABLE(of, cc2_of_match);

static struct i2c_driver cc2_driver = {
	.driver = {
		.name	= "cc2d23",
		.of_match_table = cc2_of_match,
	},
	.probe		= cc2_probe,
	.remove		= cc2_remove,
	.id_table = cc2_id,
};
module_i2c_driver(cc2_driver);

MODULE_AUTHOR("Javier Carrasco <javier.carrasco.cruz@gamil.com>");
MODULE_DESCRIPTION("Amphenol ChipCap 2 humidity and temperature sensor driver");
MODULE_LICENSE("GPL");