Re: [PATCH v4 3/4] iio: chemical: scd30: add serial interface driver

[Andy Shevchenko]

On Wed, Jun 3, 2020 at 11:47 AM Tomasz Duszynski
<tomasz.duszynski@xxxxxxxxxxx> wrote:
>
> Add serial interface driver for the SCD30 sensor.

FWIW,
Reviewed-by: Andy Shevchenko <andy.shevchenko@xxxxxxxxx>

> Signed-off-by: Tomasz Duszynski <tomasz.duszynski@xxxxxxxxxxx>
> ---
>  MAINTAINERS                         |   1 +
>  drivers/iio/chemical/Kconfig        |  11 ++
>  drivers/iio/chemical/Makefile       |   1 +
>  drivers/iio/chemical/scd30_serial.c | 263 ++++++++++++++++++++++++++++
>  4 files changed, 276 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@xxxxxxxxx>
> 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..06f85eb1a4dd
> --- /dev/null
> +++ b/drivers/iio/chemical/scd30_serial.c
> @@ -0,0 +1,263 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Sensirion SCD30 carbon dioxide sensor serial driver
> + *
> + * Copyright (c) 2020 Tomasz Duszynski <tomasz.duszynski@xxxxxxxxxxx>
> + */
> +#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 < 0)
> +               return ret;
> +       if (ret != txsize)
> +               return -EIO;
> +
> +       ret = wait_for_completion_interruptible_timeout(&priv->meas_ready, SCD30_SERDEV_TIMEOUT);
> +       if (ret < 0)
> +               return ret;
> +       if (!ret)
> +               return -ETIMEDOUT;
> +
> +       return 0;
> +}
> +
> +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];
> +       int ret, rxsize, txsize = 2;
> +       char *rsp = response;
> +       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, rxbuf, 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@xxxxxxxxxxx>");
> +MODULE_DESCRIPTION("Sensirion SCD30 carbon dioxide sensor serial driver");
> +MODULE_LICENSE("GPL v2");
> --
> 2.27.0
>


-- 
With Best Regards,
Andy Shevchenko