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linux/drivers/iio/proximity/srf04.c

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/*
* SRF04: ultrasonic sensor for distance measuring by using GPIOs
*
* Copyright (c) 2017 Andreas Klinger <ak@it-klinger.de>
*
* 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.
*
* For details about the device see:
* http://www.robot-electronics.co.uk/htm/srf04tech.htm
*
* the measurement cycle as timing diagram looks like:
*
* +---+
* GPIO | |
* trig: --+ +------------------------------------------------------
* ^ ^
* |<->|
* udelay(10)
*
* ultra +-+ +-+ +-+
* sonic | | | | | |
* burst: ---------+ +-+ +-+ +-----------------------------------------
* .
* ultra . +-+ +-+ +-+
* sonic . | | | | | |
* echo: ----------------------------------+ +-+ +-+ +----------------
* . .
* +------------------------+
* GPIO | |
* echo: -------------------+ +---------------
* ^ ^
* interrupt interrupt
* (ts_rising) (ts_falling)
* |<---------------------->|
* pulse time measured
* --> one round trip of ultra sonic waves
*/
#include <linux/err.h>
#include <linux/gpio/consumer.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/of.h>
#include <linux/platform_device.h>
#include <linux/property.h>
#include <linux/sched.h>
#include <linux/interrupt.h>
#include <linux/delay.h>
#include <linux/iio/iio.h>
#include <linux/iio/sysfs.h>
struct srf04_data {
struct device *dev;
struct gpio_desc *gpiod_trig;
struct gpio_desc *gpiod_echo;
struct mutex lock;
int irqnr;
ktime_t ts_rising;
ktime_t ts_falling;
struct completion rising;
struct completion falling;
};
static irqreturn_t srf04_handle_irq(int irq, void *dev_id)
{
struct iio_dev *indio_dev = dev_id;
struct srf04_data *data = iio_priv(indio_dev);
ktime_t now = ktime_get();
if (gpiod_get_value(data->gpiod_echo)) {
data->ts_rising = now;
complete(&data->rising);
} else {
data->ts_falling = now;
complete(&data->falling);
}
return IRQ_HANDLED;
}
static int srf04_read(struct srf04_data *data)
{
int ret;
ktime_t ktime_dt;
u64 dt_ns;
u32 time_ns, distance_mm;
/*
* just one read-echo-cycle can take place at a time
* ==> lock against concurrent reading calls
*/
mutex_lock(&data->lock);
reinit_completion(&data->rising);
reinit_completion(&data->falling);
gpiod_set_value(data->gpiod_trig, 1);
udelay(10);
gpiod_set_value(data->gpiod_trig, 0);
/* it cannot take more than 20 ms */
ret = wait_for_completion_killable_timeout(&data->rising, HZ/50);
if (ret < 0) {
mutex_unlock(&data->lock);
return ret;
} else if (ret == 0) {
mutex_unlock(&data->lock);
return -ETIMEDOUT;
}
ret = wait_for_completion_killable_timeout(&data->falling, HZ/50);
if (ret < 0) {
mutex_unlock(&data->lock);
return ret;
} else if (ret == 0) {
mutex_unlock(&data->lock);
return -ETIMEDOUT;
}
ktime_dt = ktime_sub(data->ts_falling, data->ts_rising);
mutex_unlock(&data->lock);
dt_ns = ktime_to_ns(ktime_dt);
/*
* measuring more than 3 meters is beyond the capabilities of
* the sensor
* ==> filter out invalid results for not measuring echos of
* another us sensor
*
* formula:
* distance 3 m
* time = ---------- = --------- = 9404389 ns
* speed 319 m/s
*
* using a minimum speed at -20 °C of 319 m/s
*/
if (dt_ns > 9404389)
return -EIO;
time_ns = dt_ns;
/*
* the speed as function of the temperature is approximately:
*
* speed = 331,5 + 0,6 * Temp
* with Temp in °C
* and speed in m/s
*
* use 343 m/s as ultrasonic speed at 20 °C here in absence of the
* temperature
*
* therefore:
* time 343
* distance = ------ * -----
* 10^6 2
* with time in ns
* and distance in mm (one way)
*
* because we limit to 3 meters the multiplication with 343 just
* fits into 32 bit
*/
distance_mm = time_ns * 343 / 2000000;
return distance_mm;
}
static int srf04_read_raw(struct iio_dev *indio_dev,
struct iio_chan_spec const *channel, int *val,
int *val2, long info)
{
struct srf04_data *data = iio_priv(indio_dev);
int ret;
if (channel->type != IIO_DISTANCE)
return -EINVAL;
switch (info) {
case IIO_CHAN_INFO_RAW:
ret = srf04_read(data);
if (ret < 0)
return ret;
*val = ret;
return IIO_VAL_INT;
case IIO_CHAN_INFO_SCALE:
/*
* theoretical maximum resolution is 3 mm
* 1 LSB is 1 mm
*/
*val = 0;
*val2 = 1000;
return IIO_VAL_INT_PLUS_MICRO;
default:
return -EINVAL;
}
}
static const struct iio_info srf04_iio_info = {
.driver_module = THIS_MODULE,
.read_raw = srf04_read_raw,
};
static const struct iio_chan_spec srf04_chan_spec[] = {
{
.type = IIO_DISTANCE,
.info_mask_separate =
BIT(IIO_CHAN_INFO_RAW) |
BIT(IIO_CHAN_INFO_SCALE),
},
};
static int srf04_probe(struct platform_device *pdev)
{
struct device *dev = &pdev->dev;
struct srf04_data *data;
struct iio_dev *indio_dev;
int ret;
indio_dev = devm_iio_device_alloc(dev, sizeof(struct srf04_data));
if (!indio_dev) {
dev_err(dev, "failed to allocate IIO device\n");
return -ENOMEM;
}
data = iio_priv(indio_dev);
data->dev = dev;
mutex_init(&data->lock);
init_completion(&data->rising);
init_completion(&data->falling);
data->gpiod_trig = devm_gpiod_get(dev, "trig", GPIOD_OUT_LOW);
if (IS_ERR(data->gpiod_trig)) {
dev_err(dev, "failed to get trig-gpios: err=%ld\n",
PTR_ERR(data->gpiod_trig));
return PTR_ERR(data->gpiod_trig);
}
data->gpiod_echo = devm_gpiod_get(dev, "echo", GPIOD_IN);
if (IS_ERR(data->gpiod_echo)) {
dev_err(dev, "failed to get echo-gpios: err=%ld\n",
PTR_ERR(data->gpiod_echo));
return PTR_ERR(data->gpiod_echo);
}
if (gpiod_cansleep(data->gpiod_echo)) {
dev_err(data->dev, "cansleep-GPIOs not supported\n");
return -ENODEV;
}
data->irqnr = gpiod_to_irq(data->gpiod_echo);
if (data->irqnr < 0) {
dev_err(data->dev, "gpiod_to_irq: %d\n", data->irqnr);
return data->irqnr;
}
ret = devm_request_irq(dev, data->irqnr, srf04_handle_irq,
IRQF_TRIGGER_RISING | IRQF_TRIGGER_FALLING,
pdev->name, indio_dev);
if (ret < 0) {
dev_err(data->dev, "request_irq: %d\n", ret);
return ret;
}
platform_set_drvdata(pdev, indio_dev);
indio_dev->name = "srf04";
indio_dev->dev.parent = &pdev->dev;
indio_dev->info = &srf04_iio_info;
indio_dev->modes = INDIO_DIRECT_MODE;
indio_dev->channels = srf04_chan_spec;
indio_dev->num_channels = ARRAY_SIZE(srf04_chan_spec);
return devm_iio_device_register(dev, indio_dev);
}
static const struct of_device_id of_srf04_match[] = {
{ .compatible = "devantech,srf04", },
{},
};
MODULE_DEVICE_TABLE(of, of_srf04_match);
static struct platform_driver srf04_driver = {
.probe = srf04_probe,
.driver = {
.name = "srf04-gpio",
.of_match_table = of_srf04_match,
},
};
module_platform_driver(srf04_driver);
MODULE_AUTHOR("Andreas Klinger <ak@it-klinger.de>");
MODULE_DESCRIPTION("SRF04 ultrasonic sensor for distance measuring using GPIOs");
MODULE_LICENSE("GPL");
MODULE_ALIAS("platform:srf04");
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