411 lines
10 KiB
C
411 lines
10 KiB
C
// SPDX-License-Identifier: GPL-2.0-or-later
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/*
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* SRF04: ultrasonic sensor for distance measuring by using GPIOs
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*
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* Copyright (c) 2017 Andreas Klinger <ak@it-klinger.de>
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*
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* For details about the device see:
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* https://www.robot-electronics.co.uk/htm/srf04tech.htm
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*
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* the measurement cycle as timing diagram looks like:
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*
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* +---+
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* GPIO | |
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* trig: --+ +------------------------------------------------------
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* ^ ^
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* |<->|
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* udelay(trigger_pulse_us)
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*
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* ultra +-+ +-+ +-+
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* sonic | | | | | |
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* burst: ---------+ +-+ +-+ +-----------------------------------------
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* .
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* ultra . +-+ +-+ +-+
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* sonic . | | | | | |
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* echo: ----------------------------------+ +-+ +-+ +----------------
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* . .
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* +------------------------+
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* GPIO | |
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* echo: -------------------+ +---------------
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* ^ ^
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* interrupt interrupt
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* (ts_rising) (ts_falling)
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* |<---------------------->|
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* pulse time measured
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* --> one round trip of ultra sonic waves
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*/
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#include <linux/err.h>
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#include <linux/gpio/consumer.h>
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#include <linux/kernel.h>
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#include <linux/module.h>
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#include <linux/of.h>
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#include <linux/of_device.h>
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#include <linux/platform_device.h>
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#include <linux/property.h>
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#include <linux/sched.h>
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#include <linux/interrupt.h>
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#include <linux/delay.h>
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#include <linux/pm_runtime.h>
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#include <linux/iio/iio.h>
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#include <linux/iio/sysfs.h>
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struct srf04_cfg {
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unsigned long trigger_pulse_us;
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};
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struct srf04_data {
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struct device *dev;
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struct gpio_desc *gpiod_trig;
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struct gpio_desc *gpiod_echo;
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struct gpio_desc *gpiod_power;
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struct mutex lock;
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int irqnr;
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ktime_t ts_rising;
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ktime_t ts_falling;
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struct completion rising;
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struct completion falling;
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const struct srf04_cfg *cfg;
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int startup_time_ms;
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};
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static const struct srf04_cfg srf04_cfg = {
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.trigger_pulse_us = 10,
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};
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static const struct srf04_cfg mb_lv_cfg = {
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.trigger_pulse_us = 20,
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};
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static irqreturn_t srf04_handle_irq(int irq, void *dev_id)
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{
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struct iio_dev *indio_dev = dev_id;
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struct srf04_data *data = iio_priv(indio_dev);
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ktime_t now = ktime_get();
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if (gpiod_get_value(data->gpiod_echo)) {
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data->ts_rising = now;
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complete(&data->rising);
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} else {
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data->ts_falling = now;
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complete(&data->falling);
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}
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return IRQ_HANDLED;
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}
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static int srf04_read(struct srf04_data *data)
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{
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int ret;
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ktime_t ktime_dt;
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u64 dt_ns;
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u32 time_ns, distance_mm;
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if (data->gpiod_power) {
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ret = pm_runtime_resume_and_get(data->dev);
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if (ret < 0)
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return ret;
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}
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/*
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* just one read-echo-cycle can take place at a time
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* ==> lock against concurrent reading calls
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*/
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mutex_lock(&data->lock);
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reinit_completion(&data->rising);
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reinit_completion(&data->falling);
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gpiod_set_value(data->gpiod_trig, 1);
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udelay(data->cfg->trigger_pulse_us);
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gpiod_set_value(data->gpiod_trig, 0);
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if (data->gpiod_power) {
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pm_runtime_mark_last_busy(data->dev);
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pm_runtime_put_autosuspend(data->dev);
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}
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/* it should not take more than 20 ms until echo is rising */
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ret = wait_for_completion_killable_timeout(&data->rising, HZ/50);
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if (ret < 0) {
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mutex_unlock(&data->lock);
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return ret;
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} else if (ret == 0) {
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mutex_unlock(&data->lock);
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return -ETIMEDOUT;
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}
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/* it cannot take more than 50 ms until echo is falling */
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ret = wait_for_completion_killable_timeout(&data->falling, HZ/20);
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if (ret < 0) {
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mutex_unlock(&data->lock);
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return ret;
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} else if (ret == 0) {
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mutex_unlock(&data->lock);
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return -ETIMEDOUT;
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}
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ktime_dt = ktime_sub(data->ts_falling, data->ts_rising);
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mutex_unlock(&data->lock);
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dt_ns = ktime_to_ns(ktime_dt);
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/*
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* measuring more than 6,45 meters is beyond the capabilities of
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* the supported sensors
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* ==> filter out invalid results for not measuring echos of
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* another us sensor
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*
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* formula:
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* distance 6,45 * 2 m
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* time = ---------- = ------------ = 40438871 ns
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* speed 319 m/s
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*
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* using a minimum speed at -20 °C of 319 m/s
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*/
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if (dt_ns > 40438871)
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return -EIO;
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time_ns = dt_ns;
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/*
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* the speed as function of the temperature is approximately:
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*
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* speed = 331,5 + 0,6 * Temp
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* with Temp in °C
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* and speed in m/s
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*
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* use 343,5 m/s as ultrasonic speed at 20 °C here in absence of the
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* temperature
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*
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* therefore:
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* time 343,5 time * 106
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* distance = ------ * ------- = ------------
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* 10^6 2 617176
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* with time in ns
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* and distance in mm (one way)
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*
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* because we limit to 6,45 meters the multiplication with 106 just
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* fits into 32 bit
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*/
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distance_mm = time_ns * 106 / 617176;
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return distance_mm;
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}
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static int srf04_read_raw(struct iio_dev *indio_dev,
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struct iio_chan_spec const *channel, int *val,
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int *val2, long info)
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{
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struct srf04_data *data = iio_priv(indio_dev);
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int ret;
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if (channel->type != IIO_DISTANCE)
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return -EINVAL;
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switch (info) {
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case IIO_CHAN_INFO_RAW:
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ret = srf04_read(data);
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if (ret < 0)
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return ret;
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*val = ret;
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return IIO_VAL_INT;
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case IIO_CHAN_INFO_SCALE:
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/*
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* theoretical maximum resolution is 3 mm
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* 1 LSB is 1 mm
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*/
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*val = 0;
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*val2 = 1000;
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return IIO_VAL_INT_PLUS_MICRO;
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default:
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return -EINVAL;
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}
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}
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static const struct iio_info srf04_iio_info = {
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.read_raw = srf04_read_raw,
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};
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static const struct iio_chan_spec srf04_chan_spec[] = {
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{
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.type = IIO_DISTANCE,
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.info_mask_separate =
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BIT(IIO_CHAN_INFO_RAW) |
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BIT(IIO_CHAN_INFO_SCALE),
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},
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};
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static const struct of_device_id of_srf04_match[] = {
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{ .compatible = "devantech,srf04", .data = &srf04_cfg},
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{ .compatible = "maxbotix,mb1000", .data = &mb_lv_cfg},
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{ .compatible = "maxbotix,mb1010", .data = &mb_lv_cfg},
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{ .compatible = "maxbotix,mb1020", .data = &mb_lv_cfg},
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{ .compatible = "maxbotix,mb1030", .data = &mb_lv_cfg},
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{ .compatible = "maxbotix,mb1040", .data = &mb_lv_cfg},
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{},
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};
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MODULE_DEVICE_TABLE(of, of_srf04_match);
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static int srf04_probe(struct platform_device *pdev)
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{
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struct device *dev = &pdev->dev;
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struct srf04_data *data;
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struct iio_dev *indio_dev;
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int ret;
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indio_dev = devm_iio_device_alloc(dev, sizeof(struct srf04_data));
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if (!indio_dev) {
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dev_err(dev, "failed to allocate IIO device\n");
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return -ENOMEM;
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}
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data = iio_priv(indio_dev);
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data->dev = dev;
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data->cfg = of_match_device(of_srf04_match, dev)->data;
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mutex_init(&data->lock);
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init_completion(&data->rising);
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init_completion(&data->falling);
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data->gpiod_trig = devm_gpiod_get(dev, "trig", GPIOD_OUT_LOW);
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if (IS_ERR(data->gpiod_trig)) {
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dev_err(dev, "failed to get trig-gpios: err=%ld\n",
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PTR_ERR(data->gpiod_trig));
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return PTR_ERR(data->gpiod_trig);
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}
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data->gpiod_echo = devm_gpiod_get(dev, "echo", GPIOD_IN);
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if (IS_ERR(data->gpiod_echo)) {
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dev_err(dev, "failed to get echo-gpios: err=%ld\n",
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PTR_ERR(data->gpiod_echo));
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return PTR_ERR(data->gpiod_echo);
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}
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data->gpiod_power = devm_gpiod_get_optional(dev, "power",
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GPIOD_OUT_LOW);
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if (IS_ERR(data->gpiod_power)) {
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dev_err(dev, "failed to get power-gpios: err=%ld\n",
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PTR_ERR(data->gpiod_power));
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return PTR_ERR(data->gpiod_power);
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}
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if (data->gpiod_power) {
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if (of_property_read_u32(dev->of_node, "startup-time-ms",
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&data->startup_time_ms))
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data->startup_time_ms = 100;
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dev_dbg(dev, "using power gpio: startup-time-ms=%d\n",
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data->startup_time_ms);
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}
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if (gpiod_cansleep(data->gpiod_echo)) {
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dev_err(data->dev, "cansleep-GPIOs not supported\n");
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return -ENODEV;
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}
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data->irqnr = gpiod_to_irq(data->gpiod_echo);
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if (data->irqnr < 0) {
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dev_err(data->dev, "gpiod_to_irq: %d\n", data->irqnr);
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return data->irqnr;
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}
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ret = devm_request_irq(dev, data->irqnr, srf04_handle_irq,
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IRQF_TRIGGER_RISING | IRQF_TRIGGER_FALLING,
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pdev->name, indio_dev);
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if (ret < 0) {
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dev_err(data->dev, "request_irq: %d\n", ret);
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return ret;
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}
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platform_set_drvdata(pdev, indio_dev);
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indio_dev->name = "srf04";
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indio_dev->info = &srf04_iio_info;
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indio_dev->modes = INDIO_DIRECT_MODE;
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indio_dev->channels = srf04_chan_spec;
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indio_dev->num_channels = ARRAY_SIZE(srf04_chan_spec);
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ret = iio_device_register(indio_dev);
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if (ret < 0) {
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dev_err(data->dev, "iio_device_register: %d\n", ret);
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return ret;
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}
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if (data->gpiod_power) {
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pm_runtime_set_autosuspend_delay(data->dev, 1000);
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pm_runtime_use_autosuspend(data->dev);
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ret = pm_runtime_set_active(data->dev);
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if (ret) {
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dev_err(data->dev, "pm_runtime_set_active: %d\n", ret);
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iio_device_unregister(indio_dev);
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}
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pm_runtime_enable(data->dev);
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pm_runtime_idle(data->dev);
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}
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return ret;
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}
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static int srf04_remove(struct platform_device *pdev)
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{
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struct iio_dev *indio_dev = platform_get_drvdata(pdev);
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struct srf04_data *data = iio_priv(indio_dev);
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iio_device_unregister(indio_dev);
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if (data->gpiod_power) {
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pm_runtime_disable(data->dev);
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pm_runtime_set_suspended(data->dev);
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}
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return 0;
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}
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static int __maybe_unused srf04_pm_runtime_suspend(struct device *dev)
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{
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struct platform_device *pdev = container_of(dev,
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struct platform_device, dev);
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struct iio_dev *indio_dev = platform_get_drvdata(pdev);
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struct srf04_data *data = iio_priv(indio_dev);
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gpiod_set_value(data->gpiod_power, 0);
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return 0;
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}
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static int __maybe_unused srf04_pm_runtime_resume(struct device *dev)
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{
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struct platform_device *pdev = container_of(dev,
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struct platform_device, dev);
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struct iio_dev *indio_dev = platform_get_drvdata(pdev);
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struct srf04_data *data = iio_priv(indio_dev);
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gpiod_set_value(data->gpiod_power, 1);
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msleep(data->startup_time_ms);
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return 0;
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}
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static const struct dev_pm_ops srf04_pm_ops = {
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SET_RUNTIME_PM_OPS(srf04_pm_runtime_suspend,
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srf04_pm_runtime_resume, NULL)
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};
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static struct platform_driver srf04_driver = {
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.probe = srf04_probe,
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.remove = srf04_remove,
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.driver = {
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.name = "srf04-gpio",
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.of_match_table = of_srf04_match,
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.pm = &srf04_pm_ops,
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},
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};
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module_platform_driver(srf04_driver);
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MODULE_AUTHOR("Andreas Klinger <ak@it-klinger.de>");
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MODULE_DESCRIPTION("SRF04 ultrasonic sensor for distance measuring using GPIOs");
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MODULE_LICENSE("GPL");
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MODULE_ALIAS("platform:srf04");
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