sht15.c

/*
 * sht15.c - support for the SHT15 Temperature and Humidity Sensor
 *
 * Copyright (c) 2009 Jonathan Cameron
 *
 * Copyright (c) 2007 Wouter Horre
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 *
 * For further information, see the Documentation/hwmon/sht15 file.
 */

#include <linux/interrupt.h>
#include <linux/irq.h>
#include <linux/gpio.h>
#include <linux/module.h>
#include <linux/init.h>
#include <linux/hwmon.h>
#include <linux/hwmon-sysfs.h>
#include <linux/mutex.h>
#include <linux/platform_device.h>
#include <linux/sched.h>
#include <linux/delay.h>
#include <linux/jiffies.h>
#include <linux/err.h>
#include <linux/sht15.h>
#include <linux/regulator/consumer.h>
#include <linux/slab.h>
#include <asm/atomic.h>

/* Commands */
#define SHT15_MEASURE_TEMP		0x03
#define SHT15_MEASURE_RH		0x05

/* Min timings */
#define SHT15_TSCKL			100	/* (nsecs) clock low */
#define SHT15_TSCKH			100	/* (nsecs) clock high */
#define SHT15_TSU			150	/* (nsecs) data setup time */

/* Actions the driver may be doing */
enum sht15_state {
	SHT15_READING_NOTHING,
	SHT15_READING_TEMP,
	SHT15_READING_HUMID
};

/**
 * struct sht15_temppair - elements of voltage dependent temp calc
 * @vdd:	supply voltage in microvolts
 * @d1:		see data sheet
 */
struct sht15_temppair {
	int vdd; /* microvolts */
	int d1;
};

/* Table 9 from datasheet - relates temperature calculation to supply voltage */
static const struct sht15_temppair temppoints[] = {
	{ 2500000, -39400 },
	{ 3000000, -39600 },
	{ 3500000, -39700 },
	{ 4000000, -39800 },
	{ 5000000, -40100 },
};

/**
 * struct sht15_data - device instance specific data
 * @pdata:		platform data (gpio's etc).
 * @read_work:		bh of interrupt handler.
 * @wait_queue:		wait queue for getting values from device.
 * @val_temp:		last temperature value read from device.
 * @val_humid:		last humidity value read from device.
 * @state:		state identifying the action the driver is doing.
 * @measurements_valid:	are the current stored measures valid (start condition).
 * @last_measurement:	time of last measure.
 * @read_lock:		mutex to ensure only one read in progress at a time.
 * @dev:		associate device structure.
 * @hwmon_dev:		device associated with hwmon subsystem.
 * @reg:		associated regulator (if specified).
 * @nb:			notifier block to handle notifications of voltage
 *                      changes.
 * @supply_uV:		local copy of supply voltage used to allow use of
 *                      regulator consumer if available.
 * @supply_uV_valid:	indicates that an updated value has not yet been
 *			obtained from the regulator and so any calculations
 *			based upon it will be invalid.
 * @update_supply_work:	work struct that is used to update the supply_uV.
 * @interrupt_handled:	flag used to indicate a handler has been scheduled.
 */
struct sht15_data {
	struct sht15_platform_data	*pdata;
	struct work_struct		read_work;
	wait_queue_head_t		wait_queue;
	uint16_t			val_temp;
	uint16_t			val_humid;
	enum sht15_state		state;
	bool				measurements_valid;
	unsigned long			last_measurement;
	struct mutex			read_lock;
	struct device			*dev;
	struct device			*hwmon_dev;
	struct regulator		*reg;
	struct notifier_block		nb;
	int				supply_uV;
	bool				supply_uV_valid;
	struct work_struct		update_supply_work;
	atomic_t			interrupt_handled;
};

/**
 * sht15_connection_reset() - reset the comms interface
 * @data:	sht15 specific data
 *
 * This implements section 3.4 of the data sheet
 */
static void sht15_connection_reset(struct sht15_data *data)
{
	int i;

	gpio_direction_output(data->pdata->gpio_data, 1);
	ndelay(SHT15_TSCKL);
	gpio_set_value(data->pdata->gpio_sck, 0);
	ndelay(SHT15_TSCKL);
	for (i = 0; i < 9; ++i) {
		gpio_set_value(data->pdata->gpio_sck, 1);
		ndelay(SHT15_TSCKH);
		gpio_set_value(data->pdata->gpio_sck, 0);
		ndelay(SHT15_TSCKL);
	}
}

/**
 * sht15_send_bit() - send an individual bit to the device
 * @data:	device state data
 * @val:	value of bit to be sent
 */
static inline void sht15_send_bit(struct sht15_data *data, int val)
{
	gpio_set_value(data->pdata->gpio_data, val);
	ndelay(SHT15_TSU);
	gpio_set_value(data->pdata->gpio_sck, 1);
	ndelay(SHT15_TSCKH);
	gpio_set_value(data->pdata->gpio_sck, 0);
	ndelay(SHT15_TSCKL); /* clock low time */
}

/**
 * sht15_transmission_start() - specific sequence for new transmission
 * @data:	device state data
 *
 * Timings for this are not documented on the data sheet, so very
 * conservative ones used in implementation. This implements
 * figure 12 on the data sheet.
 */
static void sht15_transmission_start(struct sht15_data *data)
{
	/* ensure data is high and output */
	gpio_direction_output(data->pdata->gpio_data, 1);
	ndelay(SHT15_TSU);
	gpio_set_value(data->pdata->gpio_sck, 0);
	ndelay(SHT15_TSCKL);
	gpio_set_value(data->pdata->gpio_sck, 1);
	ndelay(SHT15_TSCKH);
	gpio_set_value(data->pdata->gpio_data, 0);
	ndelay(SHT15_TSU);
	gpio_set_value(data->pdata->gpio_sck, 0);
	ndelay(SHT15_TSCKL);
	gpio_set_value(data->pdata->gpio_sck, 1);
	ndelay(SHT15_TSCKH);
	gpio_set_value(data->pdata->gpio_data, 1);
	ndelay(SHT15_TSU);
	gpio_set_value(data->pdata->gpio_sck, 0);
	ndelay(SHT15_TSCKL);
}

/**
 * sht15_send_byte() - send a single byte to the device
 * @data:	device state
 * @byte:	value to be sent
 */
static void sht15_send_byte(struct sht15_data *data, u8 byte)
{
	int i;

	for (i = 0; i < 8; i++) {
		sht15_send_bit(data, !!(byte & 0x80));
		byte <<= 1;
	}
}

/**
 * sht15_wait_for_response() - checks for ack from device
 * @data:	device state
 */
static int sht15_wait_for_response(struct sht15_data *data)
{
	gpio_direction_input(data->pdata->gpio_data);
	gpio_set_value(data->pdata->gpio_sck, 1);
	ndelay(SHT15_TSCKH);
	if (gpio_get_value(data->pdata->gpio_data)) {
		gpio_set_value(data->pdata->gpio_sck, 0);
		dev_err(data->dev, "Command not acknowledged\n");
		sht15_connection_reset(data);
		return -EIO;
	}
	gpio_set_value(data->pdata->gpio_sck, 0);
	ndelay(SHT15_TSCKL);
	return 0;
}

/**
 * sht15_send_cmd() - Sends a command to the device.
 * @data:	device state
 * @cmd:	command byte to be sent
 *
 * On entry, sck is output low, data is output pull high
 * and the interrupt disabled.
 */
static int sht15_send_cmd(struct sht15_data *data, u8 cmd)
{
	int ret = 0;

	sht15_transmission_start(data);
	sht15_send_byte(data, cmd);
	ret = sht15_wait_for_response(data);
	return ret;
}

/**
 * sht15_measurement() - get a new value from device
 * @data:		device instance specific data
 * @command:		command sent to request value
 * @timeout_msecs:	timeout after which comms are assumed
 *			to have failed are reset.
 */
static int sht15_measurement(struct sht15_data *data,
			     int command,
			     int timeout_msecs)
{
	int ret;

	ret = sht15_send_cmd(data, command);
	if (ret)
		return ret;

	gpio_direction_input(data->pdata->gpio_data);
	atomic_set(&data->interrupt_handled, 0);

	enable_irq(gpio_to_irq(data->pdata->gpio_data));
	if (gpio_get_value(data->pdata->gpio_data) == 0) {
		disable_irq_nosync(gpio_to_irq(data->pdata->gpio_data));
		/* Only relevant if the interrupt hasn't occurred. */
		if (!atomic_read(&data->interrupt_handled))
			schedule_work(&data->read_work);
	}
	ret = wait_event_timeout(data->wait_queue,
				 (data->state == SHT15_READING_NOTHING),
				 msecs_to_jiffies(timeout_msecs));
	if (ret == 0) {/* timeout occurred */
		disable_irq_nosync(gpio_to_irq(data->pdata->gpio_data));
		sht15_connection_reset(data);
		return -ETIME;
	}
	return 0;
}

/**
 * sht15_update_measurements() - get updated measures from device if too old
 * @data:	device state
 */
static int sht15_update_measurements(struct sht15_data *data)
{
	int ret = 0;
	int timeout = HZ;

	mutex_lock(&data->read_lock);
	if (time_after(jiffies, data->last_measurement + timeout)
	    || !data->measurements_valid) {
		data->state = SHT15_READING_HUMID;
		ret = sht15_measurement(data, SHT15_MEASURE_RH, 160);
		if (ret)
			goto error_ret;
		data->state = SHT15_READING_TEMP;
		ret = sht15_measurement(data, SHT15_MEASURE_TEMP, 400);
		if (ret)
			goto error_ret;
		data->measurements_valid = true;
		data->last_measurement = jiffies;
	}
error_ret:
	mutex_unlock(&data->read_lock);

	return ret;
}

/**
 * sht15_calc_temp() - convert the raw reading to a temperature
 * @data:	device state
 *
 * As per section 4.3 of the data sheet.
 */
static inline int sht15_calc_temp(struct sht15_data *data)
{
	int d1 = temppoints[0].d1;
	int i;

	for (i = ARRAY_SIZE(temppoints) - 1; i > 0; i--)
		/* Find pointer to interpolate */
		if (data->supply_uV > temppoints[i - 1].vdd) {
			d1 = (data->supply_uV - temppoints[i - 1].vdd)
				* (temppoints[i].d1 - temppoints[i - 1].d1)
				/ (temppoints[i].vdd - temppoints[i - 1].vdd)
				+ temppoints[i - 1].d1;
			break;
		}

	return data->val_temp * 10 + d1;
}

/**
 * sht15_calc_humid() - using last temperature convert raw to humid
 * @data:	device state
 *
 * This is the temperature compensated version as per section 4.2 of
 * the data sheet.
 *
 * The sensor is assumed to be V3, which is compatible with V4.
 * Humidity conversion coefficients are shown in table 7 of the datasheet.
 */
static inline int sht15_calc_humid(struct sht15_data *data)
{
	int rh_linear; /* milli percent */
	int temp = sht15_calc_temp(data);

	const int c1 = -4;
	const int c2 = 40500; /* x 10 ^ -6 */
	const int c3 = -28;   /* x 10 ^ -7 */

	rh_linear = c1 * 1000
		+ c2 * data->val_humid / 1000
		+ (data->val_humid * data->val_humid * c3) / 10000;
	return (temp - 25000) * (10000 + 80 * data->val_humid)
		/ 1000000 + rh_linear;
}

/**
 * sht15_show_temp() - show temperature measurement value in sysfs
 * @dev:	device.
 * @attr:	device attribute.
 * @buf:	sysfs buffer where measurement values are written to.
 *
 * Will be called on read access to temp1_input sysfs attribute.
 * Returns number of bytes written into buffer, negative errno on error.
 */
static ssize_t sht15_show_temp(struct device *dev,
			       struct device_attribute *attr,
			       char *buf)
{
	int ret;
	struct sht15_data *data = dev_get_drvdata(dev);

	/* Technically no need to read humidity as well */
	ret = sht15_update_measurements(data);

	return ret ? ret : sprintf(buf, "%d\n",
				   sht15_calc_temp(data));
}

/**
 * sht15_show_humidity() - show humidity measurement value in sysfs
 * @dev:	device.
 * @attr:	device attribute.
 * @buf:	sysfs buffer where measurement values are written to.
 *
 * Will be called on read access to humidity1_input sysfs attribute.
 * Returns number of bytes written into buffer, negative errno on error.
 */
static ssize_t sht15_show_humidity(struct device *dev,
				   struct device_attribute *attr,
				   char *buf)
{
	int ret;
	struct sht15_data *data = dev_get_drvdata(dev);

	ret = sht15_update_measurements(data);

	return ret ? ret : sprintf(buf, "%d\n", sht15_calc_humid(data));

}

static ssize_t show_name(struct device *dev,
			 struct device_attribute *attr,
			 char *buf)
{
	struct platform_device *pdev = to_platform_device(dev);
	return sprintf(buf, "%s\n", pdev->name);
}

static SENSOR_DEVICE_ATTR(temp1_input, S_IRUGO,
			  sht15_show_temp, NULL, 0);
static SENSOR_DEVICE_ATTR(humidity1_input, S_IRUGO,
			  sht15_show_humidity, NULL, 0);
static DEVICE_ATTR(name, S_IRUGO, show_name, NULL);
static struct attribute *sht15_attrs[] = {
	&sensor_dev_attr_temp1_input.dev_attr.attr,
	&sensor_dev_attr_humidity1_input.dev_attr.attr,
	&dev_attr_name.attr,
	NULL,
};

static const struct attribute_group sht15_attr_group = {
	.attrs = sht15_attrs,
};

static irqreturn_t sht15_interrupt_fired(int irq, void *d)
{
	struct sht15_data *data = d;

	/* First disable the interrupt */
	disable_irq_nosync(irq);
	atomic_inc(&data->interrupt_handled);
	/* Then schedule a reading work struct */
	if (data->state != SHT15_READING_NOTHING)
		schedule_work(&data->read_work);
	return IRQ_HANDLED;
}

/**
 * sht15_ack() - Send an ack to the device
 *
 * Each byte of data is acknowledged by pulling the data line
 * low for one clock pulse.
 */
static void sht15_ack(struct sht15_data *data)
{
	gpio_direction_output(data->pdata->gpio_data, 0);
	ndelay(SHT15_TSU);
	gpio_set_value(data->pdata->gpio_sck, 1);
	ndelay(SHT15_TSU);
	gpio_set_value(data->pdata->gpio_sck, 0);
	ndelay(SHT15_TSU);
	gpio_set_value(data->pdata->gpio_data, 1);

	gpio_direction_input(data->pdata->gpio_data);
}

/**
 * sht15_end_transmission() - notify device of end of transmission
 * @data:	device state
 *
 * This is basically a NAK. (single clock pulse, data high)
 */
static void sht15_end_transmission(struct sht15_data *data)
{
	gpio_direction_output(data->pdata->gpio_data, 1);
	ndelay(SHT15_TSU);
	gpio_set_value(data->pdata->gpio_sck, 1);
	ndelay(SHT15_TSCKH);
	gpio_set_value(data->pdata->gpio_sck, 0);
	ndelay(SHT15_TSCKL);
}

static void sht15_bh_read_data(struct work_struct *work_s)
{
	int i;
	uint16_t val = 0;
	struct sht15_data *data
		= container_of(work_s, struct sht15_data,
			       read_work);

	/* Firstly, verify the line is low */
	if (gpio_get_value(data->pdata->gpio_data)) {
		/*
		 * If not, then start the interrupt again - care here as could
		 * have gone low in meantime so verify it hasn't!
		 */
		atomic_set(&data->interrupt_handled, 0);
		enable_irq(gpio_to_irq(data->pdata->gpio_data));
		/* If still not occurred or another handler has been scheduled */
		if (gpio_get_value(data->pdata->gpio_data)
		    || atomic_read(&data->interrupt_handled))
			return;
	}

	/* Read the data back from the device */
	for (i = 0; i < 16; ++i) {
		val <<= 1;
		gpio_set_value(data->pdata->gpio_sck, 1);
		ndelay(SHT15_TSCKH);
		val |= !!gpio_get_value(data->pdata->gpio_data);
		gpio_set_value(data->pdata->gpio_sck, 0);
		ndelay(SHT15_TSCKL);
		if (i == 7)
			sht15_ack(data);
	}

	/* Tell the device we are done */
	sht15_end_transmission(data);

	switch (data->state) {
	case SHT15_READING_TEMP:
		data->val_temp = val;
		break;
	case SHT15_READING_HUMID:
		data->val_humid = val;
		break;
	default:
		break;
	}

	data->state = SHT15_READING_NOTHING;
	wake_up(&data->wait_queue);
}

static void sht15_update_voltage(struct work_struct *work_s)
{
	struct sht15_data *data
		= container_of(work_s, struct sht15_data,
			       update_supply_work);
	data->supply_uV = regulator_get_voltage(data->reg);
}

/**
 * sht15_invalidate_voltage() - mark supply voltage invalid when notified by reg
 * @nb:		associated notification structure
 * @event:	voltage regulator state change event code
 * @ignored:	function parameter - ignored here
 *
 * Note that as the notification code holds the regulator lock, we have
 * to schedule an update of the supply voltage rather than getting it directly.
 */
static int sht15_invalidate_voltage(struct notifier_block *nb,
				    unsigned long event,
				    void *ignored)
{
	struct sht15_data *data = container_of(nb, struct sht15_data, nb);

	if (event == REGULATOR_EVENT_VOLTAGE_CHANGE)
		data->supply_uV_valid = false;
	schedule_work(&data->update_supply_work);

	return NOTIFY_OK;
}

static int __devinit sht15_probe(struct platform_device *pdev)
{
	int ret = 0;
	struct sht15_data *data = kzalloc(sizeof(*data), GFP_KERNEL);

	if (!data) {
		ret = -ENOMEM;
		dev_err(&pdev->dev, "kzalloc failed\n");
		goto error_ret;
	}

	INIT_WORK(&data->read_work, sht15_bh_read_data);
	INIT_WORK(&data->update_supply_work, sht15_update_voltage);
	platform_set_drvdata(pdev, data);
	mutex_init(&data->read_lock);
	data->dev = &pdev->dev;
	init_waitqueue_head(&data->wait_queue);

	if (pdev->dev.platform_data == NULL) {
		dev_err(&pdev->dev, "no platform data supplied\n");
		goto err_free_data;
	}
	data->pdata = pdev->dev.platform_data;
	data->supply_uV = data->pdata->supply_mv * 1000;

	/*
	 * If a regulator is available,
	 * query what the supply voltage actually is!
	 */
	data->reg = regulator_get(data->dev, "vcc");
	if (!IS_ERR(data->reg)) {
		int voltage;

		voltage = regulator_get_voltage(data->reg);
		if (voltage)
			data->supply_uV = voltage;

		regulator_enable(data->reg);
		/*
		 * Setup a notifier block to update this if another device
		 * causes the voltage to change
		 */
		data->nb.notifier_call = &sht15_invalidate_voltage;
		ret = regulator_register_notifier(data->reg, &data->nb);
	}

	/* Try requesting the GPIOs */
	ret = gpio_request(data->pdata->gpio_sck, "SHT15 sck");
	if (ret) {
		dev_err(&pdev->dev, "gpio request failed\n");
		goto err_free_data;
	}
	gpio_direction_output(data->pdata->gpio_sck, 0);

	ret = gpio_request(data->pdata->gpio_data, "SHT15 data");
	if (ret) {
		dev_err(&pdev->dev, "gpio request failed\n");
		goto err_release_gpio_sck;
	}
	ret = sysfs_create_group(&pdev->dev.kobj, &sht15_attr_group);
	if (ret) {
		dev_err(&pdev->dev, "sysfs create failed");
		goto err_release_gpio_data;
	}

	ret = request_irq(gpio_to_irq(data->pdata->gpio_data),
			  sht15_interrupt_fired,
			  IRQF_TRIGGER_FALLING,
			  "sht15 data",
			  data);
	if (ret) {
		dev_err(&pdev->dev, "failed to get irq for data line\n");
		goto err_release_gpio_data;
	}
	disable_irq_nosync(gpio_to_irq(data->pdata->gpio_data));
	sht15_connection_reset(data);
	sht15_send_cmd(data, 0x1E);

	data->hwmon_dev = hwmon_device_register(data->dev);
	if (IS_ERR(data->hwmon_dev)) {
		ret = PTR_ERR(data->hwmon_dev);
		goto err_release_irq;
	}

	return 0;

err_release_irq:
	free_irq(gpio_to_irq(data->pdata->gpio_data), data);
err_release_gpio_data:
	gpio_free(data->pdata->gpio_data);
err_release_gpio_sck:
	gpio_free(data->pdata->gpio_sck);
err_free_data:
	kfree(data);
error_ret:
	return ret;
}

static int __devexit sht15_remove(struct platform_device *pdev)
{
	struct sht15_data *data = platform_get_drvdata(pdev);

	/*
	 * Make sure any reads from the device are done and
	 * prevent new ones beginning
	 */
	mutex_lock(&data->read_lock);
	hwmon_device_unregister(data->hwmon_dev);
	sysfs_remove_group(&pdev->dev.kobj, &sht15_attr_group);
	if (!IS_ERR(data->reg)) {
		regulator_unregister_notifier(data->reg, &data->nb);
		regulator_disable(data->reg);
		regulator_put(data->reg);
	}

	free_irq(gpio_to_irq(data->pdata->gpio_data), data);
	gpio_free(data->pdata->gpio_data);
	gpio_free(data->pdata->gpio_sck);
	mutex_unlock(&data->read_lock);
	kfree(data);

	return 0;
}

/*
 * sht_drivers simultaneously refers to __devinit and __devexit function
 * which causes spurious section mismatch warning. So use __refdata to
 * get rid from this.
 */
static struct platform_driver __refdata sht_drivers[] = {
	{
		.driver = {
			.name = "sht10",
			.owner = THIS_MODULE,
		},
		.probe = sht15_probe,
		.remove = __devexit_p(sht15_remove),
	}, {
		.driver = {
			.name = "sht11",
			.owner = THIS_MODULE,
		},
		.probe = sht15_probe,
		.remove = __devexit_p(sht15_remove),
	}, {
		.driver = {
			.name = "sht15",
			.owner = THIS_MODULE,
		},
		.probe = sht15_probe,
		.remove = __devexit_p(sht15_remove),
	}, {
		.driver = {
			.name = "sht71",
			.owner = THIS_MODULE,
		},
		.probe = sht15_probe,
		.remove = __devexit_p(sht15_remove),
	}, {
		.driver = {
			.name = "sht75",
			.owner = THIS_MODULE,
		},
		.probe = sht15_probe,
		.remove = __devexit_p(sht15_remove),
	},
};

static int __init sht15_init(void)
{
	int ret;
	int i;

	for (i = 0; i < ARRAY_SIZE(sht_drivers); i++) {
		ret = platform_driver_register(&sht_drivers[i]);
		if (ret)
			goto error_unreg;
	}

	return 0;

error_unreg:
	while (--i >= 0)
		platform_driver_unregister(&sht_drivers[i]);

	return ret;
}
module_init(sht15_init);

static void __exit sht15_exit(void)
{
	int i;
	for (i = ARRAY_SIZE(sht_drivers) - 1; i >= 0; i--)
		platform_driver_unregister(&sht_drivers[i]);
}
module_exit(sht15_exit);

MODULE_LICENSE("GPL");