[linux-2.6-block.git] / drivers / iio / humidity / dht11.c

/*
 * DHT11/DHT22 bit banging GPIO driver
 *
 * Copyright (c) Harald Geyer <harald@ccbib.org>
 *
 * 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.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
 * GNU General Public License for more details.
 */

#include <linux/err.h>
#include <linux/interrupt.h>
#include <linux/device.h>
#include <linux/kernel.h>
#include <linux/printk.h>
#include <linux/slab.h>
#include <linux/of.h>
#include <linux/of_device.h>
#include <linux/sysfs.h>
#include <linux/io.h>
#include <linux/module.h>
#include <linux/platform_device.h>
#include <linux/wait.h>
#include <linux/bitops.h>
#include <linux/completion.h>
#include <linux/mutex.h>
#include <linux/delay.h>
#include <linux/gpio.h>
#include <linux/of_gpio.h>
#include <linux/timekeeping.h>

#include <linux/iio/iio.h>

#define DRIVER_NAME	"dht11"

#define DHT11_DATA_VALID_TIME	2000000000  /* 2s in ns */

#define DHT11_EDGES_PREAMBLE 2
#define DHT11_BITS_PER_READ 40
/*
 * Note that when reading the sensor actually 84 edges are detected, but
 * since the last edge is not significant, we only store 83:
 */
#define DHT11_EDGES_PER_READ (2 * DHT11_BITS_PER_READ + \
			      DHT11_EDGES_PREAMBLE + 1)

/* Data transmission timing (nano seconds) */
#define DHT11_START_TRANSMISSION	18  /* ms */
#define DHT11_SENSOR_RESPONSE	80000
#define DHT11_START_BIT		50000
#define DHT11_DATA_BIT_LOW	27000
#define DHT11_DATA_BIT_HIGH	70000

struct dht11 {
	struct device			*dev;

	int				gpio;
	int				irq;

	struct completion		completion;
	/* The iio sysfs interface doesn't prevent concurrent reads: */
	struct mutex			lock;

	s64				timestamp;
	int				temperature;
	int				humidity;

	/* num_edges: -1 means "no transmission in progress" */
	int				num_edges;
	struct {s64 ts; int value; }	edges[DHT11_EDGES_PER_READ];
};

static unsigned char dht11_decode_byte(int *timing, int threshold)
{
	unsigned char ret = 0;
	int i;

	for (i = 0; i < 8; ++i) {
		ret <<= 1;
		if (timing[i] >= threshold)
			++ret;
	}

	return ret;
}

static int dht11_decode(struct dht11 *dht11, int offset, int timeres)
{
	int i, t, timing[DHT11_BITS_PER_READ], threshold;
	unsigned char temp_int, temp_dec, hum_int, hum_dec, checksum;

	threshold = DHT11_DATA_BIT_HIGH / timeres;
	if (DHT11_DATA_BIT_LOW / timeres + 1 >= threshold)
		pr_err("dht11: WARNING: decoding ambiguous\n");

	/* scale down with timeres and check validity */
	for (i = 0; i < DHT11_BITS_PER_READ; ++i) {
		t = dht11->edges[offset + 2 * i + 2].ts -
			dht11->edges[offset + 2 * i + 1].ts;
		if (!dht11->edges[offset + 2 * i + 1].value)
			return -EIO;  /* lost synchronisation */
		timing[i] = t / timeres;
	}

	hum_int = dht11_decode_byte(timing, threshold);
	hum_dec = dht11_decode_byte(&timing[8], threshold);
	temp_int = dht11_decode_byte(&timing[16], threshold);
	temp_dec = dht11_decode_byte(&timing[24], threshold);
	checksum = dht11_decode_byte(&timing[32], threshold);

	if (((hum_int + hum_dec + temp_int + temp_dec) & 0xff) != checksum)
		return -EIO;

	dht11->timestamp = ktime_get_real_ns();
	if (hum_int < 20) {  /* DHT22 */
		dht11->temperature = (((temp_int & 0x7f) << 8) + temp_dec) *
					((temp_int & 0x80) ? -100 : 100);
		dht11->humidity = ((hum_int << 8) + hum_dec) * 100;
	} else if (temp_dec == 0 && hum_dec == 0) {  /* DHT11 */
		dht11->temperature = temp_int * 1000;
		dht11->humidity = hum_int * 1000;
	} else {
		dev_err(dht11->dev,
			"Don't know how to decode data: %d %d %d %d\n",
			hum_int, hum_dec, temp_int, temp_dec);
		return -EIO;
	}

	return 0;
}

/*
 * IRQ handler called on GPIO edges
 */
static irqreturn_t dht11_handle_irq(int irq, void *data)
{
	struct iio_dev *iio = data;
	struct dht11 *dht11 = iio_priv(iio);

	/* TODO: Consider making the handler safe for IRQ sharing */
	if (dht11->num_edges < DHT11_EDGES_PER_READ && dht11->num_edges >= 0) {
		dht11->edges[dht11->num_edges].ts = ktime_get_real_ns();
		dht11->edges[dht11->num_edges++].value =
						gpio_get_value(dht11->gpio);

		if (dht11->num_edges >= DHT11_EDGES_PER_READ)
			complete(&dht11->completion);
	}

	return IRQ_HANDLED;
}

static int dht11_read_raw(struct iio_dev *iio_dev,
			  const struct iio_chan_spec *chan,
			int *val, int *val2, long m)
{
	struct dht11 *dht11 = iio_priv(iio_dev);
	int ret, timeres;

	mutex_lock(&dht11->lock);
	if (dht11->timestamp + DHT11_DATA_VALID_TIME < ktime_get_real_ns()) {
		timeres = ktime_get_resolution_ns();
		if (DHT11_DATA_BIT_HIGH < 2 * timeres) {
			dev_err(dht11->dev, "timeresolution %dns too low\n",
				timeres);
			/* In theory a better clock could become available
			 * at some point ... and there is no error code
			 * that really fits better.
			 */
			ret = -EAGAIN;
			goto err;
		}

		reinit_completion(&dht11->completion);

		dht11->num_edges = 0;
		ret = gpio_direction_output(dht11->gpio, 0);
		if (ret)
			goto err;
		msleep(DHT11_START_TRANSMISSION);
		ret = gpio_direction_input(dht11->gpio);
		if (ret)
			goto err;

		ret = request_irq(dht11->irq, dht11_handle_irq,
				  IRQF_TRIGGER_RISING | IRQF_TRIGGER_FALLING,
				  iio_dev->name, iio_dev);
		if (ret)
			goto err;

		ret = wait_for_completion_killable_timeout(&dht11->completion,
							   HZ);

		free_irq(dht11->irq, iio_dev);

		if (ret == 0 && dht11->num_edges < DHT11_EDGES_PER_READ - 1) {
			dev_err(&iio_dev->dev,
				"Only %d signal edges detected\n",
					dht11->num_edges);
			ret = -ETIMEDOUT;
		}
		if (ret < 0)
			goto err;

		ret = dht11_decode(dht11,
				   dht11->num_edges == DHT11_EDGES_PER_READ ?
					DHT11_EDGES_PREAMBLE :
					DHT11_EDGES_PREAMBLE - 2,
				timeres);
		if (ret)
			goto err;
	}

	ret = IIO_VAL_INT;
	if (chan->type == IIO_TEMP)
		*val = dht11->temperature;
	else if (chan->type == IIO_HUMIDITYRELATIVE)
		*val = dht11->humidity;
	else
		ret = -EINVAL;
err:
	dht11->num_edges = -1;
	mutex_unlock(&dht11->lock);
	return ret;
}

static const struct iio_info dht11_iio_info = {
	.driver_module		= THIS_MODULE,
	.read_raw		= dht11_read_raw,
};

static const struct iio_chan_spec dht11_chan_spec[] = {
	{ .type = IIO_TEMP,
		.info_mask_separate = BIT(IIO_CHAN_INFO_PROCESSED), },
	{ .type = IIO_HUMIDITYRELATIVE,
		.info_mask_separate = BIT(IIO_CHAN_INFO_PROCESSED), }
};

static const struct of_device_id dht11_dt_ids[] = {
	{ .compatible = "dht11", },
	{ }
};
MODULE_DEVICE_TABLE(of, dht11_dt_ids);

static int dht11_probe(struct platform_device *pdev)
{
	struct device *dev = &pdev->dev;
	struct device_node *node = dev->of_node;
	struct dht11 *dht11;
	struct iio_dev *iio;
	int ret;

	iio = devm_iio_device_alloc(dev, sizeof(*dht11));
	if (!iio) {
		dev_err(dev, "Failed to allocate IIO device\n");
		return -ENOMEM;
	}

	dht11 = iio_priv(iio);
	dht11->dev = dev;

	ret = of_get_gpio(node, 0);
	if (ret < 0)
		return ret;
	dht11->gpio = ret;
	ret = devm_gpio_request_one(dev, dht11->gpio, GPIOF_IN, pdev->name);
	if (ret)
		return ret;

	dht11->irq = gpio_to_irq(dht11->gpio);
	if (dht11->irq < 0) {
		dev_err(dev, "GPIO %d has no interrupt\n", dht11->gpio);
		return -EINVAL;
	}

	dht11->timestamp = ktime_get_real_ns() - DHT11_DATA_VALID_TIME - 1;
	dht11->num_edges = -1;

	platform_set_drvdata(pdev, iio);

	init_completion(&dht11->completion);
	mutex_init(&dht11->lock);
	iio->name = pdev->name;
	iio->dev.parent = &pdev->dev;
	iio->info = &dht11_iio_info;
	iio->modes = INDIO_DIRECT_MODE;
	iio->channels = dht11_chan_spec;
	iio->num_channels = ARRAY_SIZE(dht11_chan_spec);

	return devm_iio_device_register(dev, iio);
}

static struct platform_driver dht11_driver = {
	.driver = {
		.name	= DRIVER_NAME,
		.of_match_table = dht11_dt_ids,
	},
	.probe  = dht11_probe,
};

module_platform_driver(dht11_driver);

MODULE_AUTHOR("Harald Geyer <harald@ccbib.org>");
MODULE_DESCRIPTION("DHT11 humidity/temperature sensor driver");
MODULE_LICENSE("GPL v2");
Commit	Line	Data
091a121b HG	1	/*
	2	* DHT11/DHT22 bit banging GPIO driver
	3	*
	4	* Copyright (c) Harald Geyer <harald@ccbib.org>
	5	*
	6	* This program is free software; you can redistribute it and/or modify
	7	* it under the terms of the GNU General Public License as published by
	8	* the Free Software Foundation; either version 2 of the License, or
	9	* (at your option) any later version.
	10	*
	11	* This program is distributed in the hope that it will be useful,
	12	* but WITHOUT ANY WARRANTY; without even the implied warranty of
	13	* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
	14	* GNU General Public License for more details.
	15	*/
	16
	17	#include <linux/err.h>
	18	#include <linux/interrupt.h>
	19	#include <linux/device.h>
	20	#include <linux/kernel.h>
	21	#include <linux/printk.h>
	22	#include <linux/slab.h>
	23	#include <linux/of.h>
	24	#include <linux/of_device.h>
	25	#include <linux/sysfs.h>
	26	#include <linux/io.h>
	27	#include <linux/module.h>
	28	#include <linux/platform_device.h>
	29	#include <linux/wait.h>
	30	#include <linux/bitops.h>
	31	#include <linux/completion.h>
004bc530	32	#include <linux/mutex.h>
091a121b HG	33	#include <linux/delay.h>
	34	#include <linux/gpio.h>
	35	#include <linux/of_gpio.h>
081d9740	36	#include <linux/timekeeping.h>
091a121b HG	37
	38	#include <linux/iio/iio.h>
	39
	40	#define DRIVER_NAME "dht11"
	41
	42	#define DHT11_DATA_VALID_TIME 2000000000 /* 2s in ns */
	43
94e65519	44	#define DHT11_EDGES_PREAMBLE 2
091a121b	45	#define DHT11_BITS_PER_READ 40
94e65519 RW	46	/*
	47	* Note that when reading the sensor actually 84 edges are detected, but
	48	* since the last edge is not significant, we only store 83:
	49	*/
889c5e9b HG	50	#define DHT11_EDGES_PER_READ (2 * DHT11_BITS_PER_READ + \
889c5e9b HG	51	DHT11_EDGES_PREAMBLE + 1)
091a121b HG	52
	53	/* Data transmission timing (nano seconds) */
	54	#define DHT11_START_TRANSMISSION 18 /* ms */
	55	#define DHT11_SENSOR_RESPONSE 80000
	56	#define DHT11_START_BIT 50000
	57	#define DHT11_DATA_BIT_LOW 27000
	58	#define DHT11_DATA_BIT_HIGH 70000
	59
	60	struct dht11 {
	61	struct device *dev;
	62
	63	int gpio;
	64	int irq;
	65
	66	struct completion completion;
a7126003	67	/* The iio sysfs interface doesn't prevent concurrent reads: */
004bc530	68	struct mutex lock;
091a121b HG	69
	70	s64 timestamp;
	71	int temperature;
	72	int humidity;
	73
	74	/* num_edges: -1 means "no transmission in progress" */
	75	int num_edges;
	76	struct {s64 ts; int value; } edges[DHT11_EDGES_PER_READ];
	77	};
	78
	79	static unsigned char dht11_decode_byte(int *timing, int threshold)
	80	{
	81	unsigned char ret = 0;
	82	int i;
	83
	84	for (i = 0; i < 8; ++i) {
	85	ret <<= 1;
	86	if (timing[i] >= threshold)
	87	++ret;
	88	}
	89
	90	return ret;
	91	}
	92
081d9740	93	static int dht11_decode(struct dht11 *dht11, int offset, int timeres)
091a121b	94	{
081d9740	95	int i, t, timing[DHT11_BITS_PER_READ], threshold;
091a121b HG	96	unsigned char temp_int, temp_dec, hum_int, hum_dec, checksum;
091a121b HG	97
091a121b	98	threshold = DHT11_DATA_BIT_HIGH / timeres;
889c5e9b	99	if (DHT11_DATA_BIT_LOW / timeres + 1 >= threshold)
091a121b HG	100	pr_err("dht11: WARNING: decoding ambiguous\n");
	101
	102	/* scale down with timeres and check validity */
	103	for (i = 0; i < DHT11_BITS_PER_READ; ++i) {
889c5e9b HG	104	t = dht11->edges[offset + 2 * i + 2].ts -
	105	dht11->edges[offset + 2 * i + 1].ts;
	106	if (!dht11->edges[offset + 2 * i + 1].value)
091a121b HG	107	return -EIO; /* lost synchronisation */
	108	timing[i] = t / timeres;
	109	}
	110
	111	hum_int = dht11_decode_byte(timing, threshold);
	112	hum_dec = dht11_decode_byte(&timing[8], threshold);
	113	temp_int = dht11_decode_byte(&timing[16], threshold);
	114	temp_dec = dht11_decode_byte(&timing[24], threshold);
	115	checksum = dht11_decode_byte(&timing[32], threshold);
	116
	117	if (((hum_int + hum_dec + temp_int + temp_dec) & 0xff) != checksum)
	118	return -EIO;
	119
081d9740	120	dht11->timestamp = ktime_get_real_ns();
091a121b HG	121	if (hum_int < 20) { /* DHT22 */
	122	dht11->temperature = (((temp_int & 0x7f) << 8) + temp_dec) *
	123	((temp_int & 0x80) ? -100 : 100);
	124	dht11->humidity = ((hum_int << 8) + hum_dec) * 100;
	125	} else if (temp_dec == 0 && hum_dec == 0) { /* DHT11 */
	126	dht11->temperature = temp_int * 1000;
	127	dht11->humidity = hum_int * 1000;
	128	} else {
	129	dev_err(dht11->dev,
	130	"Don't know how to decode data: %d %d %d %d\n",
	131	hum_int, hum_dec, temp_int, temp_dec);
	132	return -EIO;
	133	}
	134
	135	return 0;
	136	}
	137
94e65519 RW	138	/*
	139	* IRQ handler called on GPIO edges
	140	*/
	141	static irqreturn_t dht11_handle_irq(int irq, void *data)
	142	{
	143	struct iio_dev *iio = data;
	144	struct dht11 *dht11 = iio_priv(iio);
	145
	146	/* TODO: Consider making the handler safe for IRQ sharing */
	147	if (dht11->num_edges < DHT11_EDGES_PER_READ && dht11->num_edges >= 0) {
081d9740	148	dht11->edges[dht11->num_edges].ts = ktime_get_real_ns();
94e65519 RW	149	dht11->edges[dht11->num_edges++].value =
	150	gpio_get_value(dht11->gpio);
	151
	152	if (dht11->num_edges >= DHT11_EDGES_PER_READ)
	153	complete(&dht11->completion);
	154	}
	155
	156	return IRQ_HANDLED;
	157	}
	158
091a121b	159	static int dht11_read_raw(struct iio_dev *iio_dev,
889c5e9b	160	const struct iio_chan_spec *chan,
091a121b HG	161	int val, int val2, long m)
	162	{
	163	struct dht11 *dht11 = iio_priv(iio_dev);
081d9740	164	int ret, timeres;
091a121b	165
004bc530	166	mutex_lock(&dht11->lock);
081d9740 HG	167	if (dht11->timestamp + DHT11_DATA_VALID_TIME < ktime_get_real_ns()) {
	168	timeres = ktime_get_resolution_ns();
	169	if (DHT11_DATA_BIT_HIGH < 2 * timeres) {
	170	dev_err(dht11->dev, "timeresolution %dns too low\n",
	171	timeres);
	172	/* In theory a better clock could become available
	173	* at some point ... and there is no error code
	174	* that really fits better.
	175	*/
	176	ret = -EAGAIN;
	177	goto err;
	178	}
	179
091a121b HG	180	reinit_completion(&dht11->completion);
	181
	182	dht11->num_edges = 0;
	183	ret = gpio_direction_output(dht11->gpio, 0);
	184	if (ret)
	185	goto err;
	186	msleep(DHT11_START_TRANSMISSION);
	187	ret = gpio_direction_input(dht11->gpio);
	188	if (ret)
	189	goto err;
	190
94e65519 RW	191	ret = request_irq(dht11->irq, dht11_handle_irq,
	192	IRQF_TRIGGER_RISING \| IRQF_TRIGGER_FALLING,
	193	iio_dev->name, iio_dev);
	194	if (ret)
	195	goto err;
	196
091a121b	197	ret = wait_for_completion_killable_timeout(&dht11->completion,
889c5e9b	198	HZ);
94e65519 RW	199
	200	free_irq(dht11->irq, iio_dev);
	201
091a121b HG	202	if (ret == 0 && dht11->num_edges < DHT11_EDGES_PER_READ - 1) {
091a121b HG	203	dev_err(&iio_dev->dev,
889c5e9b	204	"Only %d signal edges detected\n",
091a121b HG	205	dht11->num_edges);
	206	ret = -ETIMEDOUT;
	207	}
	208	if (ret < 0)
	209	goto err;
	210
	211	ret = dht11_decode(dht11,
889c5e9b	212	dht11->num_edges == DHT11_EDGES_PER_READ ?
091a121b	213	DHT11_EDGES_PREAMBLE :
081d9740 HG	214	DHT11_EDGES_PREAMBLE - 2,
081d9740 HG	215	timeres);
091a121b HG	216	if (ret)
	217	goto err;
	218	}
	219
	220	ret = IIO_VAL_INT;
	221	if (chan->type == IIO_TEMP)
	222	*val = dht11->temperature;
	223	else if (chan->type == IIO_HUMIDITYRELATIVE)
	224	*val = dht11->humidity;
	225	else
	226	ret = -EINVAL;
	227	err:
	228	dht11->num_edges = -1;
004bc530	229	mutex_unlock(&dht11->lock);
091a121b HG	230	return ret;
	231	}
	232
	233	static const struct iio_info dht11_iio_info = {
	234	.driver_module = THIS_MODULE,
	235	.read_raw = dht11_read_raw,
	236	};
	237
091a121b HG	238	static const struct iio_chan_spec dht11_chan_spec[] = {
	239	{ .type = IIO_TEMP,
	240	.info_mask_separate = BIT(IIO_CHAN_INFO_PROCESSED), },
	241	{ .type = IIO_HUMIDITYRELATIVE,
	242	.info_mask_separate = BIT(IIO_CHAN_INFO_PROCESSED), }
	243	};
	244
	245	static const struct of_device_id dht11_dt_ids[] = {
	246	{ .compatible = "dht11", },
	247	{ }
	248	};
	249	MODULE_DEVICE_TABLE(of, dht11_dt_ids);
	250
	251	static int dht11_probe(struct platform_device *pdev)
	252	{
	253	struct device *dev = &pdev->dev;
	254	struct device_node *node = dev->of_node;
	255	struct dht11 *dht11;
	256	struct iio_dev *iio;
	257	int ret;
	258
	259	iio = devm_iio_device_alloc(dev, sizeof(*dht11));
	260	if (!iio) {
	261	dev_err(dev, "Failed to allocate IIO device\n");
	262	return -ENOMEM;
	263	}
	264
	265	dht11 = iio_priv(iio);
	266	dht11->dev = dev;
	267
5fbb0bc4	268	ret = of_get_gpio(node, 0);
091a121b HG	269	if (ret < 0)
091a121b HG	270	return ret;
5fbb0bc4	271	dht11->gpio = ret;
091a121b HG	272	ret = devm_gpio_request_one(dev, dht11->gpio, GPIOF_IN, pdev->name);
	273	if (ret)
	274	return ret;
	275
	276	dht11->irq = gpio_to_irq(dht11->gpio);
	277	if (dht11->irq < 0) {
	278	dev_err(dev, "GPIO %d has no interrupt\n", dht11->gpio);
	279	return -EINVAL;
	280	}
091a121b	281
081d9740	282	dht11->timestamp = ktime_get_real_ns() - DHT11_DATA_VALID_TIME - 1;
091a121b HG	283	dht11->num_edges = -1;
	284
	285	platform_set_drvdata(pdev, iio);
	286
	287	init_completion(&dht11->completion);
004bc530	288	mutex_init(&dht11->lock);
091a121b HG	289	iio->name = pdev->name;
	290	iio->dev.parent = &pdev->dev;
	291	iio->info = &dht11_iio_info;
	292	iio->modes = INDIO_DIRECT_MODE;
	293	iio->channels = dht11_chan_spec;
	294	iio->num_channels = ARRAY_SIZE(dht11_chan_spec);
	295
	296	return devm_iio_device_register(dev, iio);
	297	}
	298
	299	static struct platform_driver dht11_driver = {
	300	.driver = {
	301	.name = DRIVER_NAME,
091a121b HG	302	.of_match_table = dht11_dt_ids,
	303	},
	304	.probe = dht11_probe,
	305	};
	306
	307	module_platform_driver(dht11_driver);
	308
	309	MODULE_AUTHOR("Harald Geyer <harald@ccbib.org>");
	310	MODULE_DESCRIPTION("DHT11 humidity/temperature sensor driver");
	311	MODULE_LICENSE("GPL v2");