iio: proximity: Add driver support for ST's VL53L0X ToF ranging sensor.

This driver was originally written by ST in 2016 as a misc input device
driver, and hasn't been maintained for a long time. I grabbed some code
from it's API and reformed it into an iio proximity device driver.
This version of driver uses i2c bus to talk to the sensor and
polling for measuring completes, so no irq line is needed.
It can be tested with reading from
/sys/bus/iio/devices/iio:deviceX/in_distance_input

Signed-off-by: Song Qiang <songqiang1304521@gmail.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

Documentation/devicetree/bindings/iio/proximity/vl53l0x.txt

@@ -0,0 +1,12 @@
+ST VL53L0X ToF ranging sensor
+
+Required properties:
+	- compatible: must be "st,vl53l0x"
+	- reg: i2c address where to find the device
+
+Example:
+
+vl53l0x@29 {
+	compatible = "st,vl53l0x";
+	reg = <0x29>;
+};

MAINTAINERS

@@ -13755,6 +13755,13 @@ L:	linux-i2c@vger.kernel.org
 S:	Maintained
 F:	drivers/i2c/busses/i2c-stm32*
 
+ST VL53L0X ToF RANGER(I2C) IIO DRIVER
+M:	Song Qiang <songqiang1304521@gmail.com>
+L:	linux-iio@vger.kernel.org
+S:	Maintained
+F:	drivers/iio/proximity/vl53l0x-i2c.c
+F:	Documentation/devicetree/bindings/iio/proximity/vl53l0x.txt
+
 STABLE BRANCH
 M:	Greg Kroah-Hartman <gregkh@linuxfoundation.org>
 L:	stable@vger.kernel.org

drivers/iio/proximity/Kconfig

@@ -92,4 +92,15 @@ config SRF08
 	  To compile this driver as a module, choose M here: the
 	  module will be called srf08.
 
+config VL53L0X_I2C
+	tristate "STMicroelectronics VL53L0X ToF ranger sensor (I2C)"
+	depends on I2C
+	help
+	  Say Y here to build a driver for STMicroelectronics VL53L0X
+	  ToF ranger sensors with i2c interface.
+	  This driver can be used to measure the distance of objects.
+
+	  To compile this driver as a module, choose M here: the
+	  module will be called vl53l0x-i2c.
+
 endmenu

drivers/iio/proximity/Makefile

@@ -11,3 +11,5 @@ obj-$(CONFIG_RFD77402)		+= rfd77402.o
 obj-$(CONFIG_SRF04)		+= srf04.o
 obj-$(CONFIG_SRF08)		+= srf08.o
 obj-$(CONFIG_SX9500)		+= sx9500.o
+obj-$(CONFIG_VL53L0X_I2C)	+= vl53l0x-i2c.o
+

drivers/iio/proximity/vl53l0x-i2c.c

@@ -0,0 +1,164 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Support for ST VL53L0X FlightSense ToF Ranging Sensor on a i2c bus.
+ *
+ * Copyright (C) 2016 STMicroelectronics Imaging Division.
+ * Copyright (C) 2018 Song Qiang <songqiang1304521@gmail.com>
+ *
+ * Datasheet available at
+ * <https://www.st.com/resource/en/datasheet/vl53l0x.pdf>
+ *
+ * Default 7-bit i2c slave address 0x29.
+ *
+ * TODO: FIFO buffer, continuous mode, interrupts, range selection,
+ * sensor ID check.
+ */
+
+#include <linux/delay.h>
+#include <linux/i2c.h>
+#include <linux/module.h>
+
+#include <linux/iio/iio.h>
+
+#define VL_REG_SYSRANGE_START				0x00
+
+#define VL_REG_SYSRANGE_MODE_MASK			GENMASK(3, 0)
+#define VL_REG_SYSRANGE_MODE_SINGLESHOT			0x00
+#define VL_REG_SYSRANGE_MODE_START_STOP			BIT(0)
+#define VL_REG_SYSRANGE_MODE_BACKTOBACK			BIT(1)
+#define VL_REG_SYSRANGE_MODE_TIMED			BIT(2)
+#define VL_REG_SYSRANGE_MODE_HISTOGRAM			BIT(3)
+
+#define VL_REG_RESULT_INT_STATUS			0x13
+#define VL_REG_RESULT_RANGE_STATUS			0x14
+#define VL_REG_RESULT_RANGE_STATUS_COMPLETE		BIT(0)
+
+struct vl53l0x_data {
+	struct i2c_client *client;
+};
+
+static int vl53l0x_read_proximity(struct vl53l0x_data *data,
+				  const struct iio_chan_spec *chan,
+				  int *val)
+{
+	struct i2c_client *client = data->client;
+	u16 tries = 20;
+	u8 buffer[12];
+	int ret;
+
+	ret = i2c_smbus_write_byte_data(client, VL_REG_SYSRANGE_START, 1);
+	if (ret < 0)
+		return ret;
+
+	do {
+		ret = i2c_smbus_read_byte_data(client,
+					       VL_REG_RESULT_RANGE_STATUS);
+		if (ret < 0)
+			return ret;
+
+		if (ret & VL_REG_RESULT_RANGE_STATUS_COMPLETE)
+			break;
+
+		usleep_range(1000, 5000);
+	} while (--tries);
+	if (!tries)
+		return -ETIMEDOUT;
+
+	ret = i2c_smbus_read_i2c_block_data(client, VL_REG_RESULT_RANGE_STATUS,
+					    12, buffer);
+	if (ret < 0)
+		return ret;
+	else if (ret != 12)
+		return -EREMOTEIO;
+
+	/* Values should be between 30~1200 in millimeters. */
+	*val = (buffer[10] << 8) + buffer[11];
+
+	return 0;
+}
+
+static const struct iio_chan_spec vl53l0x_channels[] = {
+	{
+		.type = IIO_DISTANCE,
+		.info_mask_separate = BIT(IIO_CHAN_INFO_RAW) |
+				      BIT(IIO_CHAN_INFO_SCALE),
+	},
+};
+
+static int vl53l0x_read_raw(struct iio_dev *indio_dev,
+			    const struct iio_chan_spec *chan,
+			    int *val, int *val2, long mask)
+{
+	struct vl53l0x_data *data = iio_priv(indio_dev);
+	int ret;
+
+	if (chan->type != IIO_DISTANCE)
+		return -EINVAL;
+
+	switch (mask) {
+	case IIO_CHAN_INFO_RAW:
+		ret = vl53l0x_read_proximity(data, chan, val);
+		if (ret < 0)
+			return ret;
+
+		return IIO_VAL_INT;
+	case IIO_CHAN_INFO_SCALE:
+		*val = 0;
+		*val2 = 1000;
+
+		return IIO_VAL_INT_PLUS_MICRO;
+	default:
+		return -EINVAL;
+	}
+}
+
+static const struct iio_info vl53l0x_info = {
+	.read_raw = vl53l0x_read_raw,
+};
+
+static int vl53l0x_probe(struct i2c_client *client)
+{
+	struct vl53l0x_data *data;
+	struct iio_dev *indio_dev;
+
+	indio_dev = devm_iio_device_alloc(&client->dev, sizeof(*data));
+	if (!indio_dev)
+		return -ENOMEM;
+
+	data = iio_priv(indio_dev);
+	data->client = client;
+	i2c_set_clientdata(client, indio_dev);
+
+	if (!i2c_check_functionality(client->adapter,
+				     I2C_FUNC_SMBUS_READ_I2C_BLOCK |
+				     I2C_FUNC_SMBUS_BYTE_DATA))
+		return -EOPNOTSUPP;
+
+	indio_dev->dev.parent = &client->dev;
+	indio_dev->name = "vl53l0x";
+	indio_dev->info = &vl53l0x_info;
+	indio_dev->channels = vl53l0x_channels;
+	indio_dev->num_channels = ARRAY_SIZE(vl53l0x_channels);
+	indio_dev->modes = INDIO_DIRECT_MODE;
+
+	return devm_iio_device_register(&client->dev, indio_dev);
+}
+
+static const struct of_device_id st_vl53l0x_dt_match[] = {
+	{ .compatible = "st,vl53l0x", },
+	{ }
+};
+MODULE_DEVICE_TABLE(of, st_vl53l0x_dt_match);
+
+static struct i2c_driver vl53l0x_driver = {
+	.driver = {
+		.name = "vl53l0x-i2c",
+		.of_match_table = st_vl53l0x_dt_match,
+	},
+	.probe_new = vl53l0x_probe,
+};
+module_i2c_driver(vl53l0x_driver);
+
+MODULE_AUTHOR("Song Qiang <songqiang1304521@gmail.com>");
+MODULE_DESCRIPTION("ST vl53l0x ToF ranging sensor driver");
+MODULE_LICENSE("GPL v2");