--- /dev/null
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Sensirion SPS30 particulate matter sensor serial driver
+ *
+ * Copyright (c) 2021 Tomasz Duszynski <tomasz.duszynski@octakon.com>
+ */
+#include <linux/completion.h>
+#include <linux/device.h>
+#include <linux/errno.h>
+#include <linux/iio/iio.h>
+#include <linux/minmax.h>
+#include <linux/mod_devicetable.h>
+#include <linux/module.h>
+#include <linux/serdev.h>
+#include <linux/types.h>
+
+#include "sps30.h"
+
+#define SPS30_SERIAL_DEV_NAME "sps30"
+
+#define SPS30_SERIAL_SOF_EOF 0x7e
+#define SPS30_SERIAL_TIMEOUT msecs_to_jiffies(20)
+#define SPS30_SERIAL_MAX_BUF_SIZE 263
+#define SPS30_SERIAL_ESCAPE_CHAR 0x7d
+
+#define SPS30_SERIAL_FRAME_MIN_SIZE 7
+#define SPS30_SERIAL_FRAME_ADR_OFFSET 1
+#define SPS30_SERIAL_FRAME_CMD_OFFSET 2
+#define SPS30_SERIAL_FRAME_MOSI_LEN_OFFSET 3
+#define SPS30_SERIAL_FRAME_MISO_STATE_OFFSET 3
+#define SPS30_SERIAL_FRAME_MISO_LEN_OFFSET 4
+#define SPS30_SERIAL_FRAME_MISO_DATA_OFFSET 5
+
+#define SPS30_SERIAL_START_MEAS 0x00
+#define SPS30_SERIAL_STOP_MEAS 0x01
+#define SPS30_SERIAL_READ_MEAS 0x03
+#define SPS30_SERIAL_RESET 0xd3
+#define SPS30_SERIAL_CLEAN_FAN 0x56
+#define SPS30_SERIAL_PERIOD 0x80
+#define SPS30_SERIAL_DEV_INFO 0xd0
+#define SPS30_SERIAL_READ_VERSION 0xd1
+
+struct sps30_serial_priv {
+ struct completion new_frame;
+ unsigned char buf[SPS30_SERIAL_MAX_BUF_SIZE];
+ size_t num;
+ bool escaped;
+ bool done;
+};
+
+static int sps30_serial_xfer(struct sps30_state *state, const unsigned char *buf, size_t size)
+{
+ struct serdev_device *serdev = to_serdev_device(state->dev);
+ struct sps30_serial_priv *priv = state->priv;
+ int ret;
+
+ priv->num = 0;
+ priv->escaped = false;
+ priv->done = false;
+
+ ret = serdev_device_write(serdev, buf, size, SPS30_SERIAL_TIMEOUT);
+ if (ret < 0)
+ return ret;
+ if (ret != size)
+ return -EIO;
+
+ ret = wait_for_completion_interruptible_timeout(&priv->new_frame, SPS30_SERIAL_TIMEOUT);
+ if (ret < 0)
+ return ret;
+ if (!ret)
+ return -ETIMEDOUT;
+
+ return 0;
+}
+
+static const struct {
+ unsigned char byte;
+ unsigned char byte2;
+} sps30_serial_bytes[] = {
+ { 0x11, 0x31 },
+ { 0x13, 0x33 },
+ { 0x7e, 0x5e },
+ { 0x7d, 0x5d },
+};
+
+static int sps30_serial_put_byte(unsigned char *buf, unsigned char byte)
+{
+ int i;
+
+ for (i = 0; i < ARRAY_SIZE(sps30_serial_bytes); i++) {
+ if (sps30_serial_bytes[i].byte != byte)
+ continue;
+
+ buf[0] = SPS30_SERIAL_ESCAPE_CHAR;
+ buf[1] = sps30_serial_bytes[i].byte2;
+
+ return 2;
+ }
+
+ buf[0] = byte;
+
+ return 1;
+}
+
+static char sps30_serial_get_byte(bool escaped, unsigned char byte2)
+{
+ int i;
+
+ if (!escaped)
+ return byte2;
+
+ for (i = 0; i < ARRAY_SIZE(sps30_serial_bytes); i++) {
+ if (sps30_serial_bytes[i].byte2 != byte2)
+ continue;
+
+ return sps30_serial_bytes[i].byte;
+ }
+
+ return 0;
+}
+
+static unsigned char sps30_serial_calc_chksum(const unsigned char *buf, size_t num)
+{
+ unsigned int chksum = 0;
+ size_t i;
+
+ for (i = 0; i < num; i++)
+ chksum += buf[i];
+
+ return ~chksum;
+}
+
+static int sps30_serial_prep_frame(unsigned char *buf, unsigned char cmd,
+ const unsigned char *arg, size_t arg_size)
+{
+ unsigned char chksum;
+ int num = 0;
+ size_t i;
+
+ buf[num++] = SPS30_SERIAL_SOF_EOF;
+ buf[num++] = 0;
+ num += sps30_serial_put_byte(buf + num, cmd);
+ num += sps30_serial_put_byte(buf + num, arg_size);
+
+ for (i = 0; i < arg_size; i++)
+ num += sps30_serial_put_byte(buf + num, arg[i]);
+
+ /* SOF isn't checksummed */
+ chksum = sps30_serial_calc_chksum(buf + 1, num - 1);
+ num += sps30_serial_put_byte(buf + num, chksum);
+ buf[num++] = SPS30_SERIAL_SOF_EOF;
+
+ return num;
+}
+
+static bool sps30_serial_frame_valid(struct sps30_state *state, const unsigned char *buf)
+{
+ struct sps30_serial_priv *priv = state->priv;
+ unsigned char chksum;
+
+ if ((priv->num < SPS30_SERIAL_FRAME_MIN_SIZE) ||
+ (priv->num != SPS30_SERIAL_FRAME_MIN_SIZE +
+ priv->buf[SPS30_SERIAL_FRAME_MISO_LEN_OFFSET])) {
+ dev_err(state->dev, "frame has invalid number of bytes\n");
+ return false;
+ }
+
+ if ((priv->buf[SPS30_SERIAL_FRAME_ADR_OFFSET] != buf[SPS30_SERIAL_FRAME_ADR_OFFSET]) ||
+ (priv->buf[SPS30_SERIAL_FRAME_CMD_OFFSET] != buf[SPS30_SERIAL_FRAME_CMD_OFFSET])) {
+ dev_err(state->dev, "frame has wrong ADR and CMD bytes\n");
+ return false;
+ }
+
+ if (priv->buf[SPS30_SERIAL_FRAME_MISO_STATE_OFFSET]) {
+ dev_err(state->dev, "frame with non-zero state received (0x%02x)\n",
+ priv->buf[SPS30_SERIAL_FRAME_MISO_STATE_OFFSET]);
+ return false;
+ }
+
+ /* SOF, checksum and EOF are not checksummed */
+ chksum = sps30_serial_calc_chksum(priv->buf + 1, priv->num - 3);
+ if (priv->buf[priv->num - 2] != chksum) {
+ dev_err(state->dev, "frame integrity check failed\n");
+ return false;
+ }
+
+ return true;
+}
+
+static int sps30_serial_command(struct sps30_state *state, unsigned char cmd,
+ const void *arg, size_t arg_size, void *rsp, size_t rsp_size)
+{
+ struct sps30_serial_priv *priv = state->priv;
+ unsigned char buf[SPS30_SERIAL_MAX_BUF_SIZE];
+ int ret, size;
+
+ size = sps30_serial_prep_frame(buf, cmd, arg, arg_size);
+ ret = sps30_serial_xfer(state, buf, size);
+ if (ret)
+ return ret;
+
+ if (!sps30_serial_frame_valid(state, buf))
+ return -EIO;
+
+ if (rsp) {
+ rsp_size = min_t(size_t, priv->buf[SPS30_SERIAL_FRAME_MISO_LEN_OFFSET], rsp_size);
+ memcpy(rsp, &priv->buf[SPS30_SERIAL_FRAME_MISO_DATA_OFFSET], rsp_size);
+ }
+
+ return rsp_size;
+}
+
+static int sps30_serial_receive_buf(struct serdev_device *serdev,
+ const unsigned char *buf, size_t size)
+{
+ struct iio_dev *indio_dev = dev_get_drvdata(&serdev->dev);
+ struct sps30_serial_priv *priv;
+ struct sps30_state *state;
+ unsigned char byte;
+ size_t i;
+
+ if (!indio_dev)
+ return 0;
+
+ state = iio_priv(indio_dev);
+ priv = state->priv;
+
+ /* just in case device put some unexpected data on the bus */
+ if (priv->done)
+ return size;
+
+ /* wait for the start of frame */
+ if (!priv->num && size && buf[0] != SPS30_SERIAL_SOF_EOF)
+ return 1;
+
+ if (priv->num + size >= ARRAY_SIZE(priv->buf))
+ size = ARRAY_SIZE(priv->buf) - priv->num;
+
+ for (i = 0; i < size; i++) {
+ byte = buf[i];
+ /* remove stuffed bytes on-the-fly */
+ if (byte == SPS30_SERIAL_ESCAPE_CHAR) {
+ priv->escaped = true;
+ continue;
+ }
+
+ byte = sps30_serial_get_byte(priv->escaped, byte);
+ if (priv->escaped && !byte)
+ dev_warn(state->dev, "unrecognized escaped char (0x%02x)\n", byte);
+
+ priv->buf[priv->num++] = byte;
+
+ /* EOF received */
+ if (!priv->escaped && byte == SPS30_SERIAL_SOF_EOF) {
+ if (priv->num < SPS30_SERIAL_FRAME_MIN_SIZE)
+ continue;
+
+ priv->done = true;
+ complete(&priv->new_frame);
+ i++;
+ break;
+ }
+
+ priv->escaped = false;
+ }
+
+ return i;
+}
+
+static const struct serdev_device_ops sps30_serial_device_ops = {
+ .receive_buf = sps30_serial_receive_buf,
+ .write_wakeup = serdev_device_write_wakeup,
+};
+
+static int sps30_serial_start_meas(struct sps30_state *state)
+{
+ /* request BE IEEE754 formatted data */
+ unsigned char buf[] = { 0x01, 0x03 };
+
+ return sps30_serial_command(state, SPS30_SERIAL_START_MEAS, buf, sizeof(buf), NULL, 0);
+}
+
+static int sps30_serial_stop_meas(struct sps30_state *state)
+{
+ return sps30_serial_command(state, SPS30_SERIAL_STOP_MEAS, NULL, 0, NULL, 0);
+}
+
+static int sps30_serial_reset(struct sps30_state *state)
+{
+ int ret;
+
+ ret = sps30_serial_command(state, SPS30_SERIAL_RESET, NULL, 0, NULL, 0);
+ msleep(500);
+
+ return ret;
+}
+
+static int sps30_serial_read_meas(struct sps30_state *state, __be32 *meas, size_t num)
+{
+ int ret;
+
+ /* measurements are ready within a second */
+ if (msleep_interruptible(1000))
+ return -EINTR;
+
+ ret = sps30_serial_command(state, SPS30_SERIAL_READ_MEAS, NULL, 0, meas, num * sizeof(num));
+ if (ret < 0)
+ return ret;
+ /* if measurements aren't ready sensor returns empty frame */
+ if (ret == SPS30_SERIAL_FRAME_MIN_SIZE)
+ return -ETIMEDOUT;
+ if (ret != num * sizeof(*meas))
+ return -EIO;
+
+ return 0;
+}
+
+static int sps30_serial_clean_fan(struct sps30_state *state)
+{
+ return sps30_serial_command(state, SPS30_SERIAL_CLEAN_FAN, NULL, 0, NULL, 0);
+}
+
+static int sps30_serial_read_cleaning_period(struct sps30_state *state, __be32 *period)
+{
+ unsigned char buf[] = { 0x00 };
+ int ret;
+
+ ret = sps30_serial_command(state, SPS30_SERIAL_PERIOD, buf, sizeof(buf),
+ period, sizeof(*period));
+ if (ret < 0)
+ return ret;
+ if (ret != sizeof(*period))
+ return -EIO;
+
+ return 0;
+}
+
+static int sps30_serial_write_cleaning_period(struct sps30_state *state, __be32 period)
+{
+ unsigned char buf[5] = { 0x00 };
+
+ memcpy(buf + 1, &period, sizeof(period));
+
+ return sps30_serial_command(state, SPS30_SERIAL_PERIOD, buf, sizeof(buf), NULL, 0);
+}
+
+static int sps30_serial_show_info(struct sps30_state *state)
+{
+ /*
+ * tell device do return serial number and add extra nul byte just in case
+ * serial number isn't a valid string
+ */
+ unsigned char buf[32 + 1] = { 0x03 };
+ struct device *dev = state->dev;
+ int ret;
+
+ ret = sps30_serial_command(state, SPS30_SERIAL_DEV_INFO, buf, 1, buf, sizeof(buf) - 1);
+ if (ret < 0)
+ return ret;
+ if (ret != sizeof(buf) - 1)
+ return -EIO;
+
+ dev_info(dev, "serial number: %s\n", buf);
+
+ ret = sps30_serial_command(state, SPS30_SERIAL_READ_VERSION, NULL, 0, buf, sizeof(buf) - 1);
+ if (ret < 0)
+ return ret;
+ if (ret < 2)
+ return -EIO;
+
+ dev_info(dev, "fw version: %u.%u\n", buf[0], buf[1]);
+
+ return 0;
+}
+
+static const struct sps30_ops sps30_serial_ops = {
+ .start_meas = sps30_serial_start_meas,
+ .stop_meas = sps30_serial_stop_meas,
+ .read_meas = sps30_serial_read_meas,
+ .reset = sps30_serial_reset,
+ .clean_fan = sps30_serial_clean_fan,
+ .read_cleaning_period = sps30_serial_read_cleaning_period,
+ .write_cleaning_period = sps30_serial_write_cleaning_period,
+ .show_info = sps30_serial_show_info,
+};
+
+static int sps30_serial_probe(struct serdev_device *serdev)
+{
+ struct device *dev = &serdev->dev;
+ struct sps30_serial_priv *priv;
+ int ret;
+
+ priv = devm_kzalloc(dev, sizeof(*priv), GFP_KERNEL);
+ if (!priv)
+ return -ENOMEM;
+
+ init_completion(&priv->new_frame);
+ serdev_device_set_client_ops(serdev, &sps30_serial_device_ops);
+
+ ret = devm_serdev_device_open(dev, serdev);
+ if (ret)
+ return ret;
+
+ serdev_device_set_baudrate(serdev, 115200);
+ serdev_device_set_flow_control(serdev, false);
+
+ ret = serdev_device_set_parity(serdev, SERDEV_PARITY_NONE);
+ if (ret)
+ return ret;
+
+ return sps30_probe(dev, SPS30_SERIAL_DEV_NAME, priv, &sps30_serial_ops);
+}
+
+static const struct of_device_id sps30_serial_of_match[] = {
+ { .compatible = "sensirion,sps30" },
+ { }
+};
+MODULE_DEVICE_TABLE(of, sps30_serial_of_match);
+
+static struct serdev_device_driver sps30_serial_driver = {
+ .driver = {
+ .name = KBUILD_MODNAME,
+ .of_match_table = sps30_serial_of_match,
+ },
+ .probe = sps30_serial_probe,
+};
+module_serdev_device_driver(sps30_serial_driver);
+
+MODULE_AUTHOR("Tomasz Duszynski <tomasz.duszynski@octakon.com>");
+MODULE_DESCRIPTION("Sensirion SPS30 particulate matter sensor serial driver");
+MODULE_LICENSE("GPL v2");
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