iio: sps30: separate core and interface specific code

Move code responsible for handling i2c communication to a separate file.
Rationale for this change is preparation for adding support for serial
communication.
Signed-off-by: Tomasz Duszynski <tomasz.duszynski@octakon.com>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

MAINTAINERS

@@ -16484,6 +16484,7 @@ M:	Tomasz Duszynski <tduszyns@gmail.com>
 S:	Maintained
 F:	Documentation/devicetree/bindings/iio/chemical/sensirion,sps30.yaml
 F:	drivers/iio/chemical/sps30.c
+F:	drivers/iio/chemical/sps30_i2c.c
 
 SERIAL DEVICE BUS
 M:	Rob Herring <robh@kernel.org>

drivers/iio/chemical/Kconfig

@@ -132,17 +132,21 @@ config SENSIRION_SGP30
 	  module will be called sgp30.
 
 config SPS30
-	tristate "SPS30 particulate matter sensor"
-	depends on I2C
-	select CRC8
+	tristate
 	select IIO_BUFFER
 	select IIO_TRIGGERED_BUFFER
+
+config SPS30_I2C
+	tristate "SPS30 particulate matter sensor I2C driver"
+	depends on I2C
+	select SPS30
+	select CRC8
 	help
-	  Say Y here to build support for the Sensirion SPS30 particulate
-	  matter sensor.
+	  Say Y here to build support for the Sensirion SPS30 I2C interface
+	  driver.
 
 	  To compile this driver as a module, choose M here: the module will
-	  be called sps30.
+	  be called sps30_i2c.
 
 config VZ89X
 	tristate "SGX Sensortech MiCS VZ89X VOC sensor"

drivers/iio/chemical/Makefile

@@ -17,4 +17,5 @@ obj-$(CONFIG_SCD30_I2C) += scd30_i2c.o
 obj-$(CONFIG_SCD30_SERIAL) += scd30_serial.o
 obj-$(CONFIG_SENSIRION_SGP30)	+= sgp30.o
 obj-$(CONFIG_SPS30) += sps30.o
+obj-$(CONFIG_SPS30_I2C) += sps30_i2c.o
 obj-$(CONFIG_VZ89X)		+= vz89x.o

drivers/iio/chemical/sps30.h

+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _SPS30_H
+#define _SPS30_H
+
+#include <linux/types.h>
+
+struct sps30_state;
+struct sps30_ops {
+	int (*start_meas)(struct sps30_state *state);
+	int (*stop_meas)(struct sps30_state *state);
+	int (*read_meas)(struct sps30_state *state, __be32 *meas, size_t num);
+	int (*reset)(struct sps30_state *state);
+	int (*clean_fan)(struct sps30_state *state);
+	int (*read_cleaning_period)(struct sps30_state *state, __be32 *period);
+	int (*write_cleaning_period)(struct sps30_state *state, __be32 period);
+	int (*show_info)(struct sps30_state *state);
+};
+
+struct sps30_state {
+	/* serialize access to the device */
+	struct mutex lock;
+	struct device *dev;
+	int state;
+	/*
+	 * priv pointer is solely for serdev driver private data. We keep it
+	 * here because driver_data inside dev has been already used for iio and
+	 * struct serdev_device doesn't have one.
+	 */
+	void *priv;
+	const struct sps30_ops *ops;
+};
+
+int sps30_probe(struct device *dev, const char *name, void *priv, const struct sps30_ops *ops);
+
+#endif

drivers/iio/chemical/sps30_i2c.c

+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Sensirion SPS30 particulate matter sensor i2c driver
+ *
+ * Copyright (c) 2020 Tomasz Duszynski <tomasz.duszynski@octakon.com>
+ *
+ * I2C slave address: 0x69
+ */
+#include <asm/unaligned.h>
+#include <linux/crc8.h>
+#include <linux/delay.h>
+#include <linux/device.h>
+#include <linux/errno.h>
+#include <linux/i2c.h>
+#include <linux/mod_devicetable.h>
+#include <linux/module.h>
+#include <linux/types.h>
+
+#include "sps30.h"
+
+#define SPS30_I2C_CRC8_POLYNOMIAL 0x31
+/* max number of bytes needed to store PM measurements or serial string */
+#define SPS30_I2C_MAX_BUF_SIZE 48
+
+DECLARE_CRC8_TABLE(sps30_i2c_crc8_table);
+
+#define SPS30_I2C_START_MEAS 0x0010
+#define SPS30_I2C_STOP_MEAS 0x0104
+#define SPS30_I2C_READ_MEAS 0x0300
+#define SPS30_I2C_MEAS_READY 0x0202
+#define SPS30_I2C_RESET 0xd304
+#define SPS30_I2C_CLEAN_FAN 0x5607
+#define SPS30_I2C_PERIOD 0x8004
+#define SPS30_I2C_READ_SERIAL 0xd033
+#define SPS30_I2C_READ_VERSION 0xd100
+
+static int sps30_i2c_xfer(struct sps30_state *state, unsigned char *txbuf, size_t txsize,
+			  unsigned char *rxbuf, size_t rxsize)
+{
+	struct i2c_client *client = to_i2c_client(state->dev);
+	int ret;
+
+	/*
+	 * 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(client, txbuf, txsize);
+	if (ret < 0)
+		return ret;
+	if (ret != txsize)
+		return -EIO;
+
+	if (!rxsize)
+		return 0;
+
+	ret = i2c_master_recv(client, rxbuf, rxsize);
+	if (ret < 0)
+		return ret;
+	if (ret != rxsize)
+		return -EIO;
+
+	return 0;
+}
+
+static int sps30_i2c_command(struct sps30_state *state, u16 cmd, void *arg, size_t arg_size,
+			     void *rsp, size_t rsp_size)
+{
+	/*
+	 * Internally sensor stores measurements in a following manner:
+	 *
+	 * PM1: upper two bytes, crc8, lower two bytes, crc8
+	 * PM2P5: upper two bytes, crc8, lower two bytes, crc8
+	 * PM4: 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 which we omit.
+	 */
+	unsigned char buf[SPS30_I2C_MAX_BUF_SIZE];
+	unsigned char *tmp;
+	unsigned char crc;
+	size_t i;
+	int ret;
+
+	put_unaligned_be16(cmd, buf);
+	i = 2;
+
+	if (rsp) {
+		/* each two bytes are followed by a crc8 */
+		rsp_size += rsp_size / 2;
+	} else {
+		tmp = arg;
+
+		while (arg_size) {
+			buf[i] = *tmp++;
+			buf[i + 1] = *tmp++;
+			buf[i + 2] = crc8(sps30_i2c_crc8_table, buf + i, 2, CRC8_INIT_VALUE);
+			arg_size -= 2;
+			i += 3;
+		}
+	}
+
+	ret = sps30_i2c_xfer(state, buf, i, buf, rsp_size);
+	if (ret)
+		return ret;
+
+	/* validate received data and strip off crc bytes */
+	tmp = rsp;
+	for (i = 0; i < rsp_size; i += 3) {
+		crc = crc8(sps30_i2c_crc8_table, buf + i, 2, CRC8_INIT_VALUE);
+		if (crc != buf[i + 2]) {
+			dev_err(state->dev, "data integrity check failed\n");
+			return -EIO;
+		}
+
+		*tmp++ = buf[i];
+		*tmp++ = buf[i + 1];
+	}
+
+	return 0;
+}
+
+static int sps30_i2c_start_meas(struct sps30_state *state)
+{
+	/* request BE IEEE754 formatted data */
+	unsigned char buf[] = { 0x03, 0x00 };
+
+	return sps30_i2c_command(state, SPS30_I2C_START_MEAS, buf, sizeof(buf), NULL, 0);
+}
+
+static int sps30_i2c_stop_meas(struct sps30_state *state)
+{
+	return sps30_i2c_command(state, SPS30_I2C_STOP_MEAS, NULL, 0, NULL, 0);
+}
+
+static int sps30_i2c_reset(struct sps30_state *state)
+{
+	int ret;
+
+	ret = sps30_i2c_command(state, SPS30_I2C_RESET, NULL, 0, NULL, 0);
+	msleep(500);
+	/*
+	 * Power-on-reset causes sensor to produce some glitch on i2c bus and
+	 * some controllers end up in error state. Recover simply by placing
+	 * some data on the bus, for example STOP_MEAS command, which
+	 * is NOP in this case.
+	 */
+	sps30_i2c_stop_meas(state);
+
+	return ret;
+}
+
+static bool sps30_i2c_meas_ready(struct sps30_state *state)
+{
+	unsigned char buf[2];
+	int ret;
+
+	ret = sps30_i2c_command(state, SPS30_I2C_MEAS_READY, NULL, 0, buf, sizeof(buf));
+	if (ret)
+		return false;
+
+	return buf[1];
+}
+
+static int sps30_i2c_read_meas(struct sps30_state *state, __be32 *meas, size_t num)
+{
+	/* measurements are ready within a second */
+	if (msleep_interruptible(1000))
+		return -EINTR;
+
+	if (!sps30_i2c_meas_ready(state))
+		return -ETIMEDOUT;
+
+	return sps30_i2c_command(state, SPS30_I2C_READ_MEAS, NULL, 0, meas, sizeof(num) * num);
+}
+
+static int sps30_i2c_clean_fan(struct sps30_state *state)
+{
+	return sps30_i2c_command(state, SPS30_I2C_CLEAN_FAN, NULL, 0, NULL, 0);
+}
+
+static int sps30_i2c_read_cleaning_period(struct sps30_state *state, __be32 *period)
+{
+	return sps30_i2c_command(state, SPS30_I2C_PERIOD, NULL, 0, period, sizeof(*period));
+}
+
+static int sps30_i2c_write_cleaning_period(struct sps30_state *state, __be32 period)
+{
+	return sps30_i2c_command(state, SPS30_I2C_PERIOD, &period, sizeof(period), NULL, 0);
+}
+
+static int sps30_i2c_show_info(struct sps30_state *state)
+{
+	/* extra nul just in case */
+	unsigned char buf[32 + 1] = { 0x00 };
+	int ret;
+
+	ret = sps30_i2c_command(state, SPS30_I2C_READ_SERIAL, NULL, 0, buf, sizeof(buf) - 1);
+	if (ret)
+		return ret;
+
+	dev_info(state->dev, "serial number: %s\n", buf);
+
+	ret = sps30_i2c_command(state, SPS30_I2C_READ_VERSION, NULL, 0, buf, 2);
+	if (ret)
+		return ret;
+
+	dev_info(state->dev, "fw version: %u.%u\n", buf[0], buf[1]);
+
+	return 0;
+}
+
+static const struct sps30_ops sps30_i2c_ops = {
+	.start_meas = sps30_i2c_start_meas,
+	.stop_meas = sps30_i2c_stop_meas,
+	.read_meas = sps30_i2c_read_meas,
+	.reset = sps30_i2c_reset,
+	.clean_fan = sps30_i2c_clean_fan,
+	.read_cleaning_period = sps30_i2c_read_cleaning_period,
+	.write_cleaning_period = sps30_i2c_write_cleaning_period,
+	.show_info = sps30_i2c_show_info,
+};
+
+static int sps30_i2c_probe(struct i2c_client *client)
+{
+	if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C))
+		return -EOPNOTSUPP;
+
+	crc8_populate_msb(sps30_i2c_crc8_table, SPS30_I2C_CRC8_POLYNOMIAL);
+
+	return sps30_probe(&client->dev, client->name, NULL, &sps30_i2c_ops);
+}
+
+static const struct i2c_device_id sps30_i2c_id[] = {
+	{ "sps30" },
+	{ }
+};
+MODULE_DEVICE_TABLE(i2c, sps30_i2c_id);
+
+static const struct of_device_id sps30_i2c_of_match[] = {
+	{ .compatible = "sensirion,sps30" },
+	{ }
+};
+MODULE_DEVICE_TABLE(of, sps30_i2c_of_match);
+
+static struct i2c_driver sps30_i2c_driver = {
+	.driver = {
+		.name = KBUILD_MODNAME,
+		.of_match_table = sps30_i2c_of_match,
+	},
+	.id_table = sps30_i2c_id,
+	.probe_new = sps30_i2c_probe,
+};
+module_i2c_driver(sps30_i2c_driver);
+
+MODULE_AUTHOR("Tomasz Duszynski <tomasz.duszynski@octakon.com>");
+MODULE_DESCRIPTION("Sensirion SPS30 particulate matter sensor i2c driver");
+MODULE_LICENSE("GPL v2");