// SPDX-License-Identifier: GPL-2.0-or-later
/*
 *  ads7871 - driver for TI ADS7871 A/D converter
 *
 *  Copyright (c) 2010 Paul Thomas <pthomas8589@gmail.com>
 *
 *      You need to have something like this in struct spi_board_info
 *      {
 *              .modalias       = "ads7871",
 *              .max_speed_hz   = 2*1000*1000,
 *              .chip_select    = 0,
 *              .bus_num        = 1,
 *      },
 */

/*From figure 18 in the datasheet*/
/*Register addresses*/
#define REG_LS_BYTE     0 /*A/D Output Data, LS Byte*/
#define REG_MS_BYTE     1 /*A/D Output Data, MS Byte*/
#define REG_PGA_VALID   2 /*PGA Valid Register*/
#define REG_AD_CONTROL  3 /*A/D Control Register*/
#define REG_GAIN_MUX    4 /*Gain/Mux Register*/
#define REG_IO_STATE    5 /*Digital I/O State Register*/
#define REG_IO_CONTROL  6 /*Digital I/O Control Register*/
#define REG_OSC_CONTROL 7 /*Rev/Oscillator Control Register*/
#define REG_SER_CONTROL 24 /*Serial Interface Control Register*/
#define REG_ID          31 /*ID Register*/

/*
 * From figure 17 in the datasheet
 * These bits get ORed with the address to form
 * the instruction byte
 */
/*Instruction Bit masks*/
#define INST_MODE_BM    (1 << 7)
#define INST_READ_BM    (1 << 6)
#define INST_16BIT_BM   (1 << 5)

/*From figure 18 in the datasheet*/
/*bit masks for Rev/Oscillator Control Register*/
#define MUX_CNV_BV      7
#define MUX_CNV_BM      (1 << MUX_CNV_BV)
#define MUX_M3_BM       (1 << 3) /*M3 selects single ended*/
#define MUX_G_BV        4 /*allows for reg = (gain << MUX_G_BV) | ...*/

/*From figure 18 in the datasheet*/
/*bit masks for Rev/Oscillator Control Register*/
#define OSC_OSCR_BM     (1 << 5)
#define OSC_OSCE_BM     (1 << 4)
#define OSC_REFE_BM     (1 << 3)
#define OSC_BUFE_BM     (1 << 2)
#define OSC_R2V_BM      (1 << 1)
#define OSC_RBG_BM      (1 << 0)

#include <linux/module.h>
#include <linux/init.h>
#include <linux/spi/spi.h>
#include <linux/hwmon.h>
#include <linux/err.h>
#include <linux/delay.h>

#define DEVICE_NAME     "ads7871"

struct ads7871_data {
        struct spi_device *spi;
        u8 tx_buf[2] ____cacheline_aligned;
};

static umode_t ads7871_is_visible(const void *data,
                                  enum hwmon_sensor_types type,
                                  u32 attr, int channel)
{
        if (type == hwmon_in && attr == hwmon_in_input)
                return 0444;

        return 0;
}

static int ads7871_read_reg8(struct spi_device *spi, int reg)
{
        int ret;
        reg = reg | INST_READ_BM;
        ret = spi_w8r8(spi, reg);
        return ret;
}

static int ads7871_read_reg16(struct spi_device *spi, int reg)
{
        int ret;

        reg = reg | INST_READ_BM | INST_16BIT_BM;
        ret = spi_w8r16(spi, reg);
        if (ret < 0)
                return ret;

        return le16_to_cpu((__force __le16)ret);
}

static int ads7871_write_reg8(struct ads7871_data *pdata, int reg, u8 val)
{
        pdata->tx_buf[0] = reg;
        pdata->tx_buf[1] = val;

        return spi_write(pdata->spi, pdata->tx_buf, 2);
}

static int ads7871_read(struct device *dev, enum hwmon_sensor_types type,
                        u32 attr, int channel, long *val)
{
        struct ads7871_data *pdata = dev_get_drvdata(dev);
        struct spi_device *spi = pdata->spi;
        int ret, raw_val, i = 0;
        u8 mux_cnv;

        if (type != hwmon_in || attr != hwmon_in_input)
                return -EOPNOTSUPP;
        /*
         * TODO: add support for conversions
         * other than single ended with a gain of 1
         */
        /*MUX_M3_BM forces single ended*/
        /*This is also where the gain of the PGA would be set*/
        ret = ads7871_write_reg8(pdata, REG_GAIN_MUX,
                                 (MUX_CNV_BM | MUX_M3_BM | channel));
        if (ret < 0)
                return ret;

        ret = ads7871_read_reg8(spi, REG_GAIN_MUX);
        if (ret < 0)
                return ret;

        mux_cnv = ((ret & MUX_CNV_BM) >> MUX_CNV_BV);
        /*
         * on 400MHz arm9 platform the conversion
         * is already done when we do this test
         */
        while ((i < 2) && mux_cnv) {
                i++;
                ret = ads7871_read_reg8(spi, REG_GAIN_MUX);
                if (ret < 0)
                        return ret;
                mux_cnv = ((ret & MUX_CNV_BM) >> MUX_CNV_BV);
                msleep_interruptible(1);
        }

        if (mux_cnv == 0) {
                raw_val = ads7871_read_reg16(spi, REG_LS_BYTE);
                if (raw_val < 0)
                        return raw_val;

                /*
                 * Use (s16) to ensure the sign bit is preserved during the shift.
                 * Report millivolts (2.5V = 2500mV).
                 */
                *val = ((s16)raw_val >> 2) * 2500 / 8192;
                return 0;
        }

        return -ETIMEDOUT;
}

static const struct hwmon_channel_info * const ads7871_info[] = {
        HWMON_CHANNEL_INFO(in,
                           HWMON_I_INPUT, HWMON_I_INPUT, HWMON_I_INPUT, HWMON_I_INPUT,
                           HWMON_I_INPUT, HWMON_I_INPUT, HWMON_I_INPUT, HWMON_I_INPUT),
        NULL
};

static const struct hwmon_ops ads7871_hwmon_ops = {
        .is_visible = ads7871_is_visible,
        .read = ads7871_read,
};

static const struct hwmon_chip_info ads7871_chip_info = {
        .ops = &ads7871_hwmon_ops,
        .info = ads7871_info,
};

static int ads7871_probe(struct spi_device *spi)
{
        struct device *dev = &spi->dev;
        int ret;
        uint8_t val;
        struct ads7871_data *pdata;
        struct device *hwmon_dev;

        /* Configure the SPI bus */
        spi->mode = (SPI_MODE_0);
        spi->bits_per_word = 8;
        spi_setup(spi);

        pdata = devm_kzalloc(dev, sizeof(*pdata), GFP_KERNEL);
        if (!pdata)
                return -ENOMEM;

        pdata->spi = spi;

        ads7871_write_reg8(pdata, REG_SER_CONTROL, 0);
        ads7871_write_reg8(pdata, REG_AD_CONTROL, 0);

        val = (OSC_OSCR_BM | OSC_OSCE_BM | OSC_REFE_BM | OSC_BUFE_BM);
        ads7871_write_reg8(pdata, REG_OSC_CONTROL, val);
        ret = ads7871_read_reg8(spi, REG_OSC_CONTROL);

        dev_dbg(dev, "REG_OSC_CONTROL write:%x, read:%x\n", val, ret);
        /*
         * because there is no other error checking on an SPI bus
         * we need to make sure we really have a chip
         */
        if (val != ret)
                return -ENODEV;

        hwmon_dev = devm_hwmon_device_register_with_info(dev, spi->modalias,
                                                         pdata,
                                                         &ads7871_chip_info,
                                                         NULL);
        return PTR_ERR_OR_ZERO(hwmon_dev);
}

static struct spi_driver ads7871_driver = {
        .driver = {
                .name = DEVICE_NAME,
        },
        .probe = ads7871_probe,
};

module_spi_driver(ads7871_driver);

MODULE_AUTHOR("Paul Thomas <pthomas8589@gmail.com>");
MODULE_DESCRIPTION("TI ADS7871 A/D driver");
MODULE_LICENSE("GPL");