[PATCH 2/3] iio: chemical: add support for Sensirion SPS30 sensor

[Tomasz Duszynski]

Add support for Sensirion SPS30 particulate matter sensor.

Signed-off-by: Tomasz Duszynski <tduszyns@xxxxxxxxx>
---
 drivers/iio/chemical/Kconfig  |  11 ++
 drivers/iio/chemical/Makefile |   1 +
 drivers/iio/chemical/sps30.c  | 359 ++++++++++++++++++++++++++++++++++
 3 files changed, 371 insertions(+)
 create mode 100644 drivers/iio/chemical/sps30.c

diff --git a/drivers/iio/chemical/Kconfig b/drivers/iio/chemical/Kconfig
index b8e005be4f87..40057ecf8130 100644
--- a/drivers/iio/chemical/Kconfig
+++ b/drivers/iio/chemical/Kconfig
@@ -61,6 +61,17 @@ config IAQCORE
 	  iAQ-Core Continuous/Pulsed VOC (Volatile Organic Compounds)
 	  sensors
 
+config SPS30
+	tristate "SPS30 Particulate Matter sensor"
+	depends on I2C
+	select CRC8
+	help
+	  Say Y here to build support for the Sensirion SPS30 Particulate
+	  Matter sensor.
+
+	  To compile this driver as a module, choose M here: the module will
+	  be called sps30.
+
 config VZ89X
 	tristate "SGX Sensortech MiCS VZ89X VOC sensor"
 	depends on I2C
diff --git a/drivers/iio/chemical/Makefile b/drivers/iio/chemical/Makefile
index 2f4c4ba4d781..9f42f4252151 100644
--- a/drivers/iio/chemical/Makefile
+++ b/drivers/iio/chemical/Makefile
@@ -9,4 +9,5 @@ obj-$(CONFIG_BME680_I2C) += bme680_i2c.o
 obj-$(CONFIG_BME680_SPI) += bme680_spi.o
 obj-$(CONFIG_CCS811)		+= ccs811.o
 obj-$(CONFIG_IAQCORE)		+= ams-iaq-core.o
+obj-$(CONFIG_SPS30) += sps30.o
 obj-$(CONFIG_VZ89X)		+= vz89x.o
diff --git a/drivers/iio/chemical/sps30.c b/drivers/iio/chemical/sps30.c
new file mode 100644
index 000000000000..bf802621ae7f
--- /dev/null
+++ b/drivers/iio/chemical/sps30.c
@@ -0,0 +1,359 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Sensirion SPS30 Particulate Matter sensor driver
+ *
+ * Copyright (c) Tomasz Duszynski <tduszyns@xxxxxxxxx>
+ *
+ * I2C slave address: 0x69
+ *
+ * TODO:
+ *  - support for turning on fan cleaning
+ *  - support for reading/setting auto cleaning interval
+ */
+
+#define pr_fmt(fmt) "sps30: " fmt
+
+#include <linux/crc8.h>
+#include <linux/delay.h>
+#include <linux/i2c.h>
+#include <linux/iio/buffer.h>
+#include <linux/iio/iio.h>
+#include <linux/iio/sysfs.h>
+#include <linux/iio/trigger_consumer.h>
+#include <linux/iio/triggered_buffer.h>
+#include <linux/module.h>
+
+#define SPS30_CRC8_POLYNOMIAL 0x31
+
+/* SPS30 commands */
+#define SPS30_START_MEAS 0x0010
+#define SPS30_STOP_MEAS 0x0104
+#define SPS30_RESET 0xd304
+#define SPS30_READ_DATA_READY_FLAG 0x0202
+#define SPS30_READ_DATA 0x0300
+#define SPS30_READ_SERIAL 0xD033
+
+#define SPS30_CHAN(_index, _mod) { \
+	.type = IIO_MASSCONCENTRATION, \
+	.modified = 1, \
+	.channel2 = IIO_MOD_ ## _mod, \
+	.info_mask_separate = BIT(IIO_CHAN_INFO_PROCESSED), \
+	.scan_index = _index, \
+	.scan_type = { \
+		.sign = 'u', \
+		.realbits = 12, \
+		.storagebits = 32, \
+		.endianness = IIO_CPU, \
+	}, \
+}
+
+enum {
+	PM1p0, /* just a placeholder */
+	PM2p5,
+	PM4p0, /* just a placeholder */
+	PM10,
+};
+
+struct sps30_state {
+	struct i2c_client *client;
+	/* guards against concurrent access to sensor registers */
+	struct mutex lock;
+};
+
+DECLARE_CRC8_TABLE(sps30_crc8_table);
+
+static int sps30_write_then_read(struct sps30_state *state, u8 *buf,
+				 int buf_size, u8 *data, int data_size)
+{
+	/* every two received data bytes are checksummed */
+	u8 tmp[data_size + data_size / 2];
+	int ret, i;
+
+	/*
+	 * Sensor does not support repeated start so instead of
+	 * sending two i2c messages in a row we just send one by one.
+	 */
+	ret = i2c_master_send(state->client, buf, buf_size);
+	if (ret != buf_size)
+		return ret < 0 ? ret : -EIO;
+
+	if (!data)
+		return 0;
+
+	ret = i2c_master_recv(state->client, tmp, sizeof(tmp));
+	if (ret != sizeof(tmp))
+		return ret < 0 ? ret : -EIO;
+
+	for (i = 0; i < sizeof(tmp); i += 3) {
+		u8 crc = crc8(sps30_crc8_table, &tmp[i], 2, CRC8_INIT_VALUE);
+
+		if (crc != tmp[i + 2]) {
+			dev_err(&state->client->dev,
+				"data integrity check failed\n");
+			return -EIO;
+		}
+
+		*data++ = tmp[i];
+		*data++ = tmp[i + 1];
+	}
+
+	return 0;
+}
+
+static int sps30_do_cmd(struct sps30_state *state, u16 cmd, u8 *data, int size)
+{
+	/* depending on the command up to 3 bytes may be needed for argument */
+	u8 buf[sizeof(cmd) + 3] = { cmd >> 8, cmd };
+
+	switch (cmd) {
+	case SPS30_START_MEAS:
+		buf[2] = 0x03;
+		buf[3] = 0x00;
+		buf[4] = 0xac; /* precomputed crc */
+		return sps30_write_then_read(state, buf, 5, NULL, 0);
+	case SPS30_STOP_MEAS:
+	case SPS30_RESET:
+		return sps30_write_then_read(state, buf, 2, NULL, 0);
+	case SPS30_READ_DATA_READY_FLAG:
+	case SPS30_READ_DATA:
+	case SPS30_READ_SERIAL:
+		return sps30_write_then_read(state, buf, 2, data, size);
+	default:
+		return -EINVAL;
+	};
+}
+
+static int sps30_ieee754_to_int(const u8 *data)
+{
+	u32 val = ((u32)data[0] << 24) | ((u32)data[1] << 16) |
+		  ((u32)data[2] << 8) | (u32)data[3],
+	    mantissa = (val << 9) >> 9;
+	int exp = (val >> 23) - 127;
+
+	if (!exp && !mantissa)
+		return 0;
+
+	if (exp < 0)
+		return 0;
+
+	return (1 << exp) + (mantissa >> (23 - exp));
+}
+
+static int sps30_do_meas(struct sps30_state *state, int *pm2p5, int *pm10)
+{
+	/*
+	 * Internally sensor stores measurements in a following manner:
+	 *
+	 * PM1p0: upper two bytes, crc8, lower two bytes, crc8
+	 * PM2p5: upper two bytes, crc8, lower two bytes, crc8
+	 * PM4p0: upper two bytes, crc8, lower two bytes, crc8
+	 * PM10:  upper two bytes, crc8, lower two bytes, crc8
+	 *
+	 * What follows next are number concentration measurements and
+	 * typical particle size measurement.
+	 *
+	 * Once data is read from sensor crc bytes are stripped off
+	 * hence we need 16 bytes of buffer space.
+	 */
+	int ret, tries = 5;
+	u8 buf[16];
+
+	while (tries--) {
+		ret = sps30_do_cmd(state, SPS30_READ_DATA_READY_FLAG, buf, 2);
+		if (ret)
+			return -EIO;
+
+		/* new measurements ready to be read */
+		if (buf[1] == 1)
+			break;
+
+		usleep_range(300000, 400000);
+	}
+
+	if (!tries)
+		return -ETIMEDOUT;
+
+	ret = sps30_do_cmd(state, SPS30_READ_DATA, buf, sizeof(buf));
+	if (ret)
+		return ret;
+
+	/*
+	 * All measurements come in IEEE754 single precision floating point
+	 * format but sensor itself is not precise enough (-+ 10% error)
+	 * to take full advantage of it. Hence converting result to int
+	 * to keep things simple.
+	 */
+	*pm2p5 = sps30_ieee754_to_int(&buf[PM2p5 * 4]);
+	*pm10 = sps30_ieee754_to_int(&buf[PM10 * 4]);
+
+	return 0;
+}
+
+static irqreturn_t sps30_trigger_handler(int irq, void *p)
+{
+	struct iio_poll_func *pf = p;
+	struct iio_dev *indio_dev = pf->indio_dev;
+	struct sps30_state *state = iio_priv(indio_dev);
+	u32 buf[4]; /* PM2p5, PM10, timestamp */
+	int ret;
+
+	mutex_lock(&state->lock);
+	ret = sps30_do_meas(state, &buf[0], &buf[1]);
+	mutex_unlock(&state->lock);
+	if (ret < 0)
+		goto err;
+
+	iio_push_to_buffers_with_timestamp(indio_dev, buf,
+					   iio_get_time_ns(indio_dev));
+err:
+	iio_trigger_notify_done(indio_dev->trig);
+
+	return IRQ_HANDLED;
+}
+
+static int sps30_read_raw(struct iio_dev *indio_dev,
+			  struct iio_chan_spec const *chan,
+			  int *val, int *val2, long mask)
+{
+	struct sps30_state *state = iio_priv(indio_dev);
+	int ret;
+
+	switch (mask) {
+	case IIO_CHAN_INFO_PROCESSED:
+		switch (chan->type) {
+		case IIO_MASSCONCENTRATION:
+			mutex_lock(&state->lock);
+			switch (chan->channel2) {
+			case IIO_MOD_PM2p5:
+				ret = sps30_do_meas(state, val, val2);
+				break;
+			case IIO_MOD_PM10:
+				ret = sps30_do_meas(state, val2, val);
+				break;
+			default:
+				break;
+			}
+			mutex_unlock(&state->lock);
+			if (ret)
+				return ret;
+
+			return IIO_VAL_INT;
+		default:
+			return -EINVAL;
+		}
+		break;
+	default:
+		return -EINVAL;
+	}
+}
+
+static const struct iio_info sps30_info = {
+	.read_raw = sps30_read_raw,
+};
+
+static const struct iio_chan_spec sps30_channels[] = {
+	SPS30_CHAN(0, PM2p5),
+	SPS30_CHAN(1, PM10),
+	IIO_CHAN_SOFT_TIMESTAMP(2),
+};
+
+static const unsigned long sps30_scan_masks[] = { 0x03, 0x00 };
+
+static int sps30_probe(struct i2c_client *client)
+{
+	struct iio_dev *indio_dev;
+	struct sps30_state *state;
+	u8 buf[32] = { };
+	int ret;
+
+	if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C))
+		return -EOPNOTSUPP;
+
+	indio_dev = devm_iio_device_alloc(&client->dev, sizeof(*state));
+	if (!indio_dev)
+		return -ENOMEM;
+
+	state = iio_priv(indio_dev);
+	i2c_set_clientdata(client, indio_dev);
+	state->client = client;
+	indio_dev->dev.parent = &client->dev;
+	indio_dev->info = &sps30_info;
+	indio_dev->name = client->name;
+	indio_dev->channels = sps30_channels;
+	indio_dev->num_channels = ARRAY_SIZE(sps30_channels);
+	indio_dev->modes = INDIO_DIRECT_MODE;
+	indio_dev->available_scan_masks = sps30_scan_masks;
+
+	mutex_init(&state->lock);
+	crc8_populate_msb(sps30_crc8_table, SPS30_CRC8_POLYNOMIAL);
+
+	/*
+	 * Power-on-reset causes sensor to produce some glitch on i2c bus
+	 * and some controllers end up in error state. Recover simply
+	 * by placing something on the bus.
+	 */
+	ret = sps30_do_cmd(state, SPS30_RESET, NULL, 0);
+	if (ret) {
+		dev_err(&client->dev, "failed to reset device\n");
+		return ret;
+	}
+	usleep_range(2500000, 3500000);
+	sps30_do_cmd(state, SPS30_STOP_MEAS, NULL, 0);
+
+	ret = sps30_do_cmd(state, SPS30_READ_SERIAL, buf, sizeof(buf));
+	if (ret) {
+		dev_err(&client->dev, "failed to read serial number\n");
+		return ret;
+	}
+	dev_info(&client->dev, "serial number: %s\n", buf);
+
+	ret = sps30_do_cmd(state, SPS30_START_MEAS, NULL, 0);
+	if (ret) {
+		dev_err(&client->dev, "failed to start measurement\n");
+		return ret;
+	}
+
+	ret = devm_iio_triggered_buffer_setup(&client->dev, indio_dev, NULL,
+					      sps30_trigger_handler, NULL);
+	if (ret)
+		return ret;
+
+	return devm_iio_device_register(&client->dev, indio_dev);
+}
+
+static int sps30_remove(struct i2c_client *client)
+{
+	struct iio_dev *indio_dev = i2c_get_clientdata(client);
+	struct sps30_state *state = iio_priv(indio_dev);
+
+	sps30_do_cmd(state, SPS30_STOP_MEAS, NULL, 0);
+
+	return 0;
+}
+
+static const struct i2c_device_id sps30_id[] = {
+	{ "sps30" },
+	{ }
+};
+MODULE_DEVICE_TABLE(i2c, sps30_id);
+
+static const struct of_device_id sps30_of_match[] = {
+	{ .compatible = "sensirion,sps30" },
+	{ }
+};
+MODULE_DEVICE_TABLE(of, sps30_of_match);
+
+static struct i2c_driver sps30_driver = {
+	.driver = {
+		.name = "sps30",
+		.of_match_table = sps30_of_match,
+	},
+	.id_table = sps30_id,
+	.probe_new = sps30_probe,
+	.remove = sps30_remove,
+};
+module_i2c_driver(sps30_driver);
+
+MODULE_AUTHOR("Tomasz Duszynski <tduszyns@xxxxxxxxx>");
+MODULE_DESCRIPTION("Sensirion SPS30 particulate matter sensor driver");
+MODULE_LICENSE("GPL v2");
-- 
2.19.2