// SPDX-License-Identifier: GPL-2.0 /* * Sensirion SCD30 carbon dioxide sensor serial driver * * Copyright (c) 2020 Tomasz Duszynski */ #include #include #include #include #include #include #include #include #include #include #include #include #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 = serdev_device_get_drvdata(serdev); 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 = pm_sleep_ptr(&scd30_pm_ops), }, .probe = scd30_serdev_probe, }; module_serdev_device_driver(scd30_serdev_driver); MODULE_AUTHOR("Tomasz Duszynski "); MODULE_DESCRIPTION("Sensirion SCD30 carbon dioxide sensor serial driver"); MODULE_LICENSE("GPL v2"); MODULE_IMPORT_NS(IIO_SCD30);