diff options
Diffstat (limited to 'drivers/iio/chemical/scd30_serial.c')
| -rw-r--r-- | drivers/iio/chemical/scd30_serial.c | 263 |
1 files changed, 263 insertions, 0 deletions
diff --git a/drivers/iio/chemical/scd30_serial.c b/drivers/iio/chemical/scd30_serial.c new file mode 100644 index 000000000..06f85eb1a --- /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@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 < 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@octakon.com>"); +MODULE_DESCRIPTION("Sensirion SCD30 carbon dioxide sensor serial driver"); +MODULE_LICENSE("GPL v2"); |