// 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/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 {
        u8 byte;
        u8 byte2;
} sps30_serial_bytes[] = {
        { 0x11, 0x31 },
        { 0x13, 0x33 },
        { 0x7e, 0x5e },
        { 0x7d, 0x5d },
};

static int sps30_serial_put_byte(u8 *buf, u8 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 u8 sps30_serial_get_byte(bool escaped, u8 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(u8 *buf, u8 cmd, const u8 *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 size_t sps30_serial_receive_buf(struct serdev_device *serdev,
                                       const u8 *buf, size_t size)
{
        struct iio_dev *indio_dev = dev_get_drvdata(&serdev->dev);
        struct sps30_serial_priv *priv;
        struct sps30_state *state;
        size_t i;
        u8 byte;

        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(*meas));
        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");
MODULE_IMPORT_NS("IIO_SPS30");