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Subject[PATCH v2 3/4] iio: chemical: scd30: add serial interface driver
Date
Add serial interface driver for the SCD30 sensor.

Signed-off-by: Tomasz Duszynski <tomasz.duszynski@octakon.com>
---
MAINTAINERS | 1 +
drivers/iio/chemical/Kconfig | 11 ++
drivers/iio/chemical/Makefile | 1 +
drivers/iio/chemical/scd30_serial.c | 266 ++++++++++++++++++++++++++++
4 files changed, 279 insertions(+)
create mode 100644 drivers/iio/chemical/scd30_serial.c

diff --git a/MAINTAINERS b/MAINTAINERS
index 13aed3473b7e..5db4b446c8ba 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -15143,6 +15143,7 @@ S: Maintained
F: drivers/iio/chemical/scd30.h
F: drivers/iio/chemical/scd30_core.c
F: drivers/iio/chemical/scd30_i2c.c
+F: drivers/iio/chemical/scd30_serial.c

SENSIRION SPS30 AIR POLLUTION SENSOR DRIVER
M: Tomasz Duszynski <tduszyns@gmail.com>
diff --git a/drivers/iio/chemical/Kconfig b/drivers/iio/chemical/Kconfig
index 970d34888c2e..10bb431bc3ce 100644
--- a/drivers/iio/chemical/Kconfig
+++ b/drivers/iio/chemical/Kconfig
@@ -107,6 +107,17 @@ config SCD30_I2C
To compile this driver as a module, choose M here: the module will
be called scd30_i2c.

+config SCD30_SERIAL
+ tristate "SCD30 carbon dioxide sensor serial driver"
+ depends on SCD30_CORE && SERIAL_DEV_BUS
+ select CRC16
+ help
+ Say Y here to build support for the Sensirion SCD30 serial interface
+ driver.
+
+ To compile this driver as a module, choose M here: the module will
+ be called scd30_serial.
+
config SENSIRION_SGP30
tristate "Sensirion SGPxx gas sensors"
depends on I2C
diff --git a/drivers/iio/chemical/Makefile b/drivers/iio/chemical/Makefile
index 0966ca34e34b..fef63dd5bf92 100644
--- a/drivers/iio/chemical/Makefile
+++ b/drivers/iio/chemical/Makefile
@@ -14,6 +14,7 @@ obj-$(CONFIG_IAQCORE) += ams-iaq-core.o
obj-$(CONFIG_PMS7003) += pms7003.o
obj-$(CONFIG_SCD30_CORE) += scd30_core.o
obj-$(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_VZ89X) += vz89x.o
diff --git a/drivers/iio/chemical/scd30_serial.c b/drivers/iio/chemical/scd30_serial.c
new file mode 100644
index 000000000000..07d7d3110fe0
--- /dev/null
+++ b/drivers/iio/chemical/scd30_serial.c
@@ -0,0 +1,266 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Sensirion SCD30 carbon dioxide sensor serial driver
+ *
+ * Copyright (c) 2020 Tomasz Duszynski <tomasz.duszynski@octakon.com>
+ */
+#include <linux/crc16.h>
+#include <linux/device.h>
+#include <linux/errno.h>
+#include <linux/iio/iio.h>
+#include <linux/jiffies.h>
+#include <linux/mod_devicetable.h>
+#include <linux/module.h>
+#include <linux/property.h>
+#include <linux/serdev.h>
+#include <linux/string.h>
+#include <linux/types.h>
+#include <asm/unaligned.h>
+
+#include "scd30.h"
+
+#define SCD30_SERDEV_ADDR 0x61
+#define SCD30_SERDEV_WRITE 0x06
+#define SCD30_SERDEV_READ 0x03
+#define SCD30_SERDEV_MAX_BUF_SIZE 17
+#define SCD30_SERDEV_RX_HEADER_SIZE 3
+#define SCD30_SERDEV_CRC_SIZE 2
+#define SCD30_SERDEV_TIMEOUT msecs_to_jiffies(200)
+
+struct scd30_serdev_priv {
+ struct completion meas_ready;
+ char *buf;
+ int num_expected;
+ int num;
+};
+
+static u16 scd30_serdev_cmd_lookup_tbl[] = {
+ [CMD_START_MEAS] = 0x0036,
+ [CMD_STOP_MEAS] = 0x0037,
+ [CMD_MEAS_INTERVAL] = 0x0025,
+ [CMD_MEAS_READY] = 0x0027,
+ [CMD_READ_MEAS] = 0x0028,
+ [CMD_ASC] = 0x003a,
+ [CMD_FRC] = 0x0039,
+ [CMD_TEMP_OFFSET] = 0x003b,
+ [CMD_FW_VERSION] = 0x0020,
+ [CMD_RESET] = 0x0034,
+};
+
+static u16 scd30_serdev_calc_crc(const char *buf, int size)
+{
+ return crc16(0xffff, buf, size);
+}
+
+static int scd30_serdev_xfer(struct scd30_state *state, char *txbuf, int txsize,
+ char *rxbuf, int rxsize)
+{
+ struct serdev_device *serdev = to_serdev_device(state->dev);
+ struct scd30_serdev_priv *priv = state->priv;
+ int ret;
+
+ priv->buf = rxbuf;
+ priv->num_expected = rxsize;
+ priv->num = 0;
+
+ ret = serdev_device_write(serdev, txbuf, txsize, SCD30_SERDEV_TIMEOUT);
+ if (ret < txsize)
+ return ret < 0 ? ret : -EIO;
+
+ ret = wait_for_completion_interruptible_timeout(&priv->meas_ready,
+ SCD30_SERDEV_TIMEOUT);
+ if (ret > 0)
+ ret = 0;
+ else if (!ret)
+ ret = -ETIMEDOUT;
+
+ return ret;
+}
+
+static int scd30_serdev_command(struct scd30_state *state, enum scd30_cmd cmd,
+ u16 arg, void *response, int size)
+{
+ /*
+ * Communication over serial line is based on modbus protocol (or rather
+ * its variation called modbus over serial to be precise). Upon
+ * receiving a request device should reply with response.
+ *
+ * Frame below represents a request message. Each field takes
+ * exactly one byte.
+ *
+ * +------+------+-----+-----+-------+-------+-----+-----+
+ * | dev | op | reg | reg | byte1 | byte0 | crc | crc |
+ * | addr | code | msb | lsb | | | lsb | msb |
+ * +------+------+-----+-----+-------+-------+-----+-----+
+ *
+ * The message device replies with depends on the 'op code' field from
+ * the request. In case it was set to SCD30_SERDEV_WRITE sensor should
+ * reply with unchanged request. Otherwise 'op code' was set to
+ * SCD30_SERDEV_READ and response looks like the one below. As with
+ * request, each field takes one byte.
+ *
+ * +------+------+--------+-------+-----+-------+-----+-----+
+ * | dev | op | num of | byte0 | ... | byteN | crc | crc |
+ * | addr | code | bytes | | | | lsb | msb |
+ * +------+------+--------+-------+-----+-------+-----+-----+
+ */
+ char txbuf[SCD30_SERDEV_MAX_BUF_SIZE] = { SCD30_SERDEV_ADDR },
+ rxbuf[SCD30_SERDEV_MAX_BUF_SIZE], *rsp = response;
+ int ret, rxsize, txsize = 2;
+ u16 crc;
+
+ put_unaligned_be16(scd30_serdev_cmd_lookup_tbl[cmd], txbuf + txsize);
+ txsize += 2;
+
+ if (rsp) {
+ txbuf[1] = SCD30_SERDEV_READ;
+ if (cmd == CMD_READ_MEAS)
+ /* number of u16 words to read */
+ put_unaligned_be16(size / 2, txbuf + txsize);
+ else
+ put_unaligned_be16(0x0001, txbuf + txsize);
+ txsize += 2;
+ crc = scd30_serdev_calc_crc(txbuf, txsize);
+ put_unaligned_le16(crc, txbuf + txsize);
+ txsize += 2;
+ rxsize = SCD30_SERDEV_RX_HEADER_SIZE + size +
+ SCD30_SERDEV_CRC_SIZE;
+ } else {
+ if ((cmd == CMD_STOP_MEAS) || (cmd == CMD_RESET))
+ arg = 0x0001;
+
+ txbuf[1] = SCD30_SERDEV_WRITE;
+ put_unaligned_be16(arg, txbuf + txsize);
+ txsize += 2;
+ crc = scd30_serdev_calc_crc(txbuf, txsize);
+ put_unaligned_le16(crc, txbuf + txsize);
+ txsize += 2;
+ rxsize = txsize;
+ }
+
+ ret = scd30_serdev_xfer(state, txbuf, txsize, rxbuf, rxsize);
+ if (ret)
+ return ret;
+
+ switch (txbuf[1]) {
+ case SCD30_SERDEV_WRITE:
+ if (memcmp(txbuf, txbuf, txsize)) {
+ dev_err(state->dev, "wrong message received\n");
+ return -EIO;
+ }
+ break;
+ case SCD30_SERDEV_READ:
+ if (rxbuf[2] != (rxsize -
+ SCD30_SERDEV_RX_HEADER_SIZE -
+ SCD30_SERDEV_CRC_SIZE)) {
+ dev_err(state->dev,
+ "received data size does not match header\n");
+ return -EIO;
+ }
+
+ rxsize -= SCD30_SERDEV_CRC_SIZE;
+ crc = get_unaligned_le16(rxbuf + rxsize);
+ if (crc != scd30_serdev_calc_crc(rxbuf, rxsize)) {
+ dev_err(state->dev, "data integrity check failed\n");
+ return -EIO;
+ }
+
+ rxsize -= SCD30_SERDEV_RX_HEADER_SIZE;
+ memcpy(rsp, rxbuf + SCD30_SERDEV_RX_HEADER_SIZE, rxsize);
+ break;
+ default:
+ dev_err(state->dev, "received unknown op code\n");
+ return -EIO;
+ }
+
+ return 0;
+}
+
+static int scd30_serdev_receive_buf(struct serdev_device *serdev,
+ const unsigned char *buf, size_t size)
+{
+ struct iio_dev *indio_dev = dev_get_drvdata(&serdev->dev);
+ struct scd30_serdev_priv *priv;
+ struct scd30_state *state;
+ int num;
+
+ if (!indio_dev)
+ return 0;
+
+ state = iio_priv(indio_dev);
+ priv = state->priv;
+
+ /* just in case sensor puts some unexpected bytes on the bus */
+ if (!priv->buf)
+ return 0;
+
+ if (priv->num + size >= priv->num_expected)
+ num = priv->num_expected - priv->num;
+ else
+ num = size;
+
+ memcpy(priv->buf + priv->num, buf, num);
+ priv->num += num;
+
+ if (priv->num == priv->num_expected) {
+ priv->buf = NULL;
+ complete(&priv->meas_ready);
+ }
+
+ return num;
+}
+
+static const struct serdev_device_ops scd30_serdev_ops = {
+ .receive_buf = scd30_serdev_receive_buf,
+ .write_wakeup = serdev_device_write_wakeup,
+};
+
+static int scd30_serdev_probe(struct serdev_device *serdev)
+{
+ struct device *dev = &serdev->dev;
+ struct scd30_serdev_priv *priv;
+ int irq, ret;
+
+ priv = devm_kzalloc(dev, sizeof(*priv), GFP_KERNEL);
+ if (!priv)
+ return -ENOMEM;
+
+ init_completion(&priv->meas_ready);
+ serdev_device_set_client_ops(serdev, &scd30_serdev_ops);
+
+ ret = devm_serdev_device_open(dev, serdev);
+ if (ret)
+ return ret;
+
+ serdev_device_set_baudrate(serdev, 19200);
+ serdev_device_set_flow_control(serdev, false);
+
+ ret = serdev_device_set_parity(serdev, SERDEV_PARITY_NONE);
+ if (ret)
+ return ret;
+
+ irq = fwnode_irq_get(dev_fwnode(dev), 0);
+
+ return scd30_probe(dev, irq, KBUILD_MODNAME, priv,
+ scd30_serdev_command);
+}
+
+static const struct of_device_id scd30_serdev_of_match[] = {
+ { .compatible = "sensirion,scd30" },
+ { }
+};
+MODULE_DEVICE_TABLE(of, scd30_serdev_of_match);
+
+static struct serdev_device_driver scd30_serdev_driver = {
+ .driver = {
+ .name = KBUILD_MODNAME,
+ .of_match_table = scd30_serdev_of_match,
+ .pm = &scd30_pm_ops,
+ },
+ .probe = scd30_serdev_probe,
+};
+module_serdev_device_driver(scd30_serdev_driver);
+
+MODULE_AUTHOR("Tomasz Duszynski <tomasz.duszynski@octakon.com>");
+MODULE_DESCRIPTION("Sensirion SCD30 carbon dioxide sensor serial driver");
+MODULE_LICENSE("GPL v2");
--
2.26.2
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