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Date:   Thu, 7 Nov 2019 14:00:47 +0100
From:   Andreas Klinger <ak@it-klinger.de>
To:     robh+dt@kernel.org, jic23@kernel.org, mark.rutland@arm.com
Cc:     mripard@kernel.org, shawnguo@kernel.org, heiko@sntech.de,
        icenowy@aosc.io, laurent.pinchart@ideasonboard.com,
        knaack.h@gmx.de, lars@metafoo.de, pmeerw@pmeerw.net,
        gregkh@linuxfoundation.org, christophe.jaillet@wanadoo.fr,
        tglx@linutronix.de, mchehab+samsung@kernel.org,
        davem@davemloft.net, paulmck@linux.ibm.com,
        devicetree@vger.kernel.org, linux-iio@vger.kernel.org,
        linux-kernel@vger.kernel.org
Subject: [PATCH 3/5] iio: ping: add parallax ping sensors
Message-ID: <20191107130045.rt3ix2atyjd3gekr@arbad>
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Sender: linux-kernel-owner@vger.kernel.org
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add support for parallax ping and laser ping sensors with just one pin
for trigger and echo signal.

This driver is based on srf04. In contrast to it it's necessary to
change direction of the pin and to request the irq just for the period
when the echo is rising and falling. Because this adds a lot of cases
there is this individual driver for handling this type of sensors.

Signed-off-by: Andreas Klinger <ak@it-klinger.de>
---
 drivers/iio/proximity/ping.c | 336 +++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 336 insertions(+)
 create mode 100644 drivers/iio/proximity/ping.c

diff --git a/drivers/iio/proximity/ping.c b/drivers/iio/proximity/ping.c
new file mode 100644
index 000000000000..1a1fbb8ab0c2
--- /dev/null
+++ b/drivers/iio/proximity/ping.c
@@ -0,0 +1,336 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * PING: ultrasonic sensor for distance measuring by using only one GPIOs
+ *
+ * Copyright (c) 2019 Andreas Klinger <ak@it-klinger.de>
+ *
+ * For details about the devices see:
+ * http://parallax.com/sites/default/files/downloads/28041-LaserPING-2m-Rangefinder-Guide.pdf
+ * http://parallax.com/sites/default/files/downloads/28015-PING-Documentation-v1.6.pdf
+ *
+ * the measurement cycle as timing diagram looks like:
+ *
+ *          +---+            +------------------------+
+ * GPIO     |   |            |                        |
+ * ping:  --+   +------------+                        +----------------
+ *          ^   ^            ^                        ^
+ *          |<->|            interrupt                interrupt
+ *         udelay(5)         (ts_rising)              (ts_falling)
+ *                           |<---------------------->|
+ *                           .  pulse time measured
+ *                           .  --> one round trip of ultra sonic waves
+ *                           .                        .
+ * ultra           +-+ +-+ +-+                        .
+ * sonic           | | | | | |                        .
+ * burst: ---------+ +-+ +-+ +-----------------------------------------
+ *                                                    .
+ * ultra                                    +-+ +-+ +-+
+ * sonic                                    | | | | | |
+ * echo:  ----------------------------------+ +-+ +-+ +----------------
+ */
+#include <linux/err.h>
+#include <linux/gpio/consumer.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/of_device.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 ping_cfg {
+	unsigned long	trigger_pulse_us;	/* length of trigger pulse */
+	int		laserping_error;	/* support error code in */
+						/*   pulse width of laser */
+						/*   ping sensors */
+	s64		timeout_ns;		/* timeout in ns */
+};
+
+struct ping_data {
+	struct device		*dev;
+	struct gpio_desc	*gpiod_ping;
+	struct mutex		lock;
+	int			irqnr;
+	ktime_t			ts_rising;
+	ktime_t			ts_falling;
+	struct completion	rising;
+	struct completion	falling;
+	const struct ping_cfg	*cfg;
+};
+
+static const struct ping_cfg pa_ping_cfg = {
+	.trigger_pulse_us	= 5,
+	.laserping_error	= 0,
+	.timeout_ns		= 18500000,	/* 3 meters */
+};
+
+static const struct ping_cfg pa_laser_ping_cfg = {
+	.trigger_pulse_us = 5,
+	.laserping_error = 1,
+	.timeout_ns		= 15500000,	/* 2 meters plus error codes */
+};
+
+static irqreturn_t ping_handle_irq(int irq, void *dev_id)
+{
+	struct iio_dev *indio_dev = dev_id;
+	struct ping_data *data = iio_priv(indio_dev);
+	ktime_t now = ktime_get();
+
+	if (gpiod_get_value(data->gpiod_ping)) {
+		data->ts_rising = now;
+		complete(&data->rising);
+	} else {
+		data->ts_falling = now;
+		complete(&data->falling);
+	}
+
+	return IRQ_HANDLED;
+}
+
+static int ping_read(struct ping_data *data)
+{
+	int ret;
+	ktime_t ktime_dt;
+	s64 dt_ns;
+	u32 time_ns, distance_mm;
+	struct platform_device *pdev = container_of(data->dev,
+						struct platform_device, dev);
+	struct iio_dev *indio_dev = iio_priv_to_dev(data);
+
+	/*
+	 * 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_ping, 1);
+	udelay(data->cfg->trigger_pulse_us);
+	gpiod_set_value(data->gpiod_ping, 0);
+
+	ret = gpiod_direction_input(data->gpiod_ping);
+	if (ret < 0) {
+		mutex_unlock(&data->lock);
+		return ret;
+	}
+
+	data->irqnr = gpiod_to_irq(data->gpiod_ping);
+	if (data->irqnr < 0) {
+		dev_err(data->dev, "gpiod_to_irq: %d\n", data->irqnr);
+		return data->irqnr;
+	}
+
+	ret = devm_request_irq(data->dev, data->irqnr, ping_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;
+	}
+
+	/* it should not take more than 20 ms until echo is rising */
+	ret = wait_for_completion_killable_timeout(&data->rising, HZ/50);
+	if (ret < 0)
+		goto err_reset_direction;
+	else if (ret == 0) {
+		ret = -ETIMEDOUT;
+		goto err_reset_direction;
+	}
+
+	/* it cannot take more than 50 ms until echo is falling */
+	ret = wait_for_completion_killable_timeout(&data->falling, HZ/20);
+	if (ret < 0)
+		goto err_reset_direction;
+	else if (ret == 0) {
+		ret = -ETIMEDOUT;
+		goto err_reset_direction;
+	}
+
+	ktime_dt = ktime_sub(data->ts_falling, data->ts_rising);
+
+	free_irq(data->irqnr, indio_dev);
+
+	ret = gpiod_direction_output(data->gpiod_ping, GPIOD_OUT_LOW);
+	if (ret < 0) {
+		mutex_unlock(&data->lock);
+		return ret;
+	}
+
+	mutex_unlock(&data->lock);
+
+	dt_ns = ktime_to_ns(ktime_dt);
+	if (dt_ns > data->cfg->timeout_ns) {
+		dev_dbg(data->dev, "distance out of range: dt=%lldns\n",
+								dt_ns);
+		return -EIO;
+	}
+
+	time_ns = dt_ns;
+
+	/*
+	 * read error code of laser ping sensor and give users chance to
+	 * figure out error by using dynamic debuggging
+	 */
+	if (data->cfg->laserping_error) {
+		if ((time_ns > 12500000) && (time_ns <= 13500000)) {
+			dev_dbg(data->dev, "target too close or to far\n");
+			return -EIO;
+		}
+		if ((time_ns > 13500000) && (time_ns <= 14500000)) {
+			dev_dbg(data->dev, "internal sensor error\n");
+			return -EIO;
+		}
+		if ((time_ns > 14500000) && (time_ns <= 15500000)) {
+			dev_dbg(data->dev, "internal sensor timeout\n");
+			return -EIO;
+		}
+	}
+
+	/*
+	 * 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 343,5 m/s as ultrasonic speed at 20 °C here in absence of the
+	 * temperature
+	 *
+	 * therefore:
+	 *             time     343,5     time * 232
+	 * distance = ------ * ------- = ------------
+	 *             10^6         2        1350800
+	 *   with time in ns
+	 *   and distance in mm (one way)
+	 *
+	 * because we limit to 3 meters the multiplication with 232 just
+	 * fits into 32 bit
+	 */
+	distance_mm = time_ns * 232 / 1350800;
+
+	return distance_mm;
+
+err_reset_direction:
+	mutex_unlock(&data->lock);
+	free_irq(data->irqnr, indio_dev);
+
+	if (gpiod_direction_output(data->gpiod_ping, GPIOD_OUT_LOW))
+		dev_dbg(data->dev, "error in gpiod_direction_output\n");
+	return ret;
+}
+
+static int ping_read_raw(struct iio_dev *indio_dev,
+			    struct iio_chan_spec const *channel, int *val,
+			    int *val2, long info)
+{
+	struct ping_data *data = iio_priv(indio_dev);
+	int ret;
+
+	if (channel->type != IIO_DISTANCE)
+		return -EINVAL;
+
+	switch (info) {
+	case IIO_CHAN_INFO_RAW:
+		ret = ping_read(data);
+		if (ret < 0)
+			return ret;
+		*val = ret;
+		return IIO_VAL_INT;
+	case IIO_CHAN_INFO_SCALE:
+		/*
+		 * maximum resolution in datasheet is 1 mm
+		 * 1 LSB is 1 mm
+		 */
+		*val = 0;
+		*val2 = 1000;
+		return IIO_VAL_INT_PLUS_MICRO;
+	default:
+		return -EINVAL;
+	}
+}
+
+static const struct iio_info ping_iio_info = {
+	.read_raw		= ping_read_raw,
+};
+
+static const struct iio_chan_spec ping_chan_spec[] = {
+	{
+		.type = IIO_DISTANCE,
+		.info_mask_separate =
+				BIT(IIO_CHAN_INFO_RAW) |
+				BIT(IIO_CHAN_INFO_SCALE),
+	},
+};
+
+static const struct of_device_id of_ping_match[] = {
+	{ .compatible = "parallax,ping", .data = &pa_ping_cfg},
+	{ .compatible = "parallax,laserping", .data = &pa_ping_cfg},
+	{},
+};
+
+MODULE_DEVICE_TABLE(of, of_ping_match);
+
+static int ping_probe(struct platform_device *pdev)
+{
+	struct device *dev = &pdev->dev;
+	struct ping_data *data;
+	struct iio_dev *indio_dev;
+
+	indio_dev = devm_iio_device_alloc(dev, sizeof(struct ping_data));
+	if (!indio_dev) {
+		dev_err(dev, "failed to allocate IIO device\n");
+		return -ENOMEM;
+	}
+
+	data = iio_priv(indio_dev);
+	data->dev = dev;
+	data->cfg = of_match_device(of_ping_match, dev)->data;
+
+	mutex_init(&data->lock);
+	init_completion(&data->rising);
+	init_completion(&data->falling);
+
+	data->gpiod_ping = devm_gpiod_get(dev, "ping", GPIOD_OUT_LOW);
+	if (IS_ERR(data->gpiod_ping)) {
+		dev_err(dev, "failed to get ping-gpios: err=%ld\n",
+						PTR_ERR(data->gpiod_ping));
+		return PTR_ERR(data->gpiod_ping);
+	}
+
+	if (gpiod_cansleep(data->gpiod_ping)) {
+		dev_err(data->dev, "cansleep-GPIOs not supported\n");
+		return -ENODEV;
+	}
+
+	platform_set_drvdata(pdev, indio_dev);
+
+	indio_dev->name = "ping";
+	indio_dev->dev.parent = &pdev->dev;
+	indio_dev->info = &ping_iio_info;
+	indio_dev->modes = INDIO_DIRECT_MODE;
+	indio_dev->channels = ping_chan_spec;
+	indio_dev->num_channels = ARRAY_SIZE(ping_chan_spec);
+
+	return devm_iio_device_register(dev, indio_dev);
+}
+
+static struct platform_driver ping_driver = {
+	.probe		= ping_probe,
+	.driver		= {
+		.name		= "ping-gpio",
+		.of_match_table	= of_ping_match,
+	},
+};
+
+module_platform_driver(ping_driver);
+
+MODULE_AUTHOR("Andreas Klinger <ak@it-klinger.de>");
+MODULE_DESCRIPTION("PING sensors for distance measuring using one GPIOs");
+MODULE_LICENSE("GPL");
+MODULE_ALIAS("platform:ping");
-- 
2.11.0