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// 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 <linux/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 size_t scd30_serdev_receive_buf(struct serdev_device *serdev,
const u8 *buf, size_t size)
{
struct iio_dev *indio_dev = serdev_device_get_drvdata(serdev);
struct scd30_serdev_priv *priv;
struct scd30_state *state;
size_t 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 = pm_sleep_ptr(&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");
MODULE_IMPORT_NS(IIO_SCD30);
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