/*
 * AD5421 Digital to analog converters  driver
 *
 * Copyright 2011 Analog Devices Inc.
 *
 * Licensed under the GPL-2.
 */

#include <linux/device.h>
#include <linux/delay.h>
#include <linux/err.h>
#include <linux/module.h>
#include <linux/interrupt.h>
#include <linux/kernel.h>
#include <linux/spi/spi.h>
#include <linux/slab.h>
#include <linux/sysfs.h>

#include <linux/iio/iio.h>
#include <linux/iio/sysfs.h>
#include <linux/iio/events.h>
#include <linux/iio/dac/ad5421.h>


#define AD5421_REG_DAC_DATA             0x1
#define AD5421_REG_CTRL                 0x2
#define AD5421_REG_OFFSET               0x3
#define AD5421_REG_GAIN                 0x4
/* load dac and fault shared the same register number. Writing to it will cause
 * a dac load command, reading from it will return the fault status register */
#define AD5421_REG_LOAD_DAC             0x5
#define AD5421_REG_FAULT                0x5
#define AD5421_REG_FORCE_ALARM_CURRENT  0x6
#define AD5421_REG_RESET                0x7
#define AD5421_REG_START_CONVERSION     0x8
#define AD5421_REG_NOOP                 0x9

#define AD5421_CTRL_WATCHDOG_DISABLE    BIT(12)
#define AD5421_CTRL_AUTO_FAULT_READBACK BIT(11)
#define AD5421_CTRL_MIN_CURRENT         BIT(9)
#define AD5421_CTRL_ADC_SOURCE_TEMP     BIT(8)
#define AD5421_CTRL_ADC_ENABLE          BIT(7)
#define AD5421_CTRL_PWR_DOWN_INT_VREF   BIT(6)

#define AD5421_FAULT_SPI                        BIT(15)
#define AD5421_FAULT_PEC                        BIT(14)
#define AD5421_FAULT_OVER_CURRENT               BIT(13)
#define AD5421_FAULT_UNDER_CURRENT              BIT(12)
#define AD5421_FAULT_TEMP_OVER_140              BIT(11)
#define AD5421_FAULT_TEMP_OVER_100              BIT(10)
#define AD5421_FAULT_UNDER_VOLTAGE_6V           BIT(9)
#define AD5421_FAULT_UNDER_VOLTAGE_12V          BIT(8)

/* These bits will cause the fault pin to go high */
#define AD5421_FAULT_TRIGGER_IRQ \
        (AD5421_FAULT_SPI | AD5421_FAULT_PEC | AD5421_FAULT_OVER_CURRENT | \
        AD5421_FAULT_UNDER_CURRENT | AD5421_FAULT_TEMP_OVER_140)

/**
 * struct ad5421_state - driver instance specific data
 * @spi:                spi_device
 * @ctrl:               control register cache
 * @current_range:      current range which the device is configured for
 * @data:               spi transfer buffers
 * @fault_mask:         software masking of events
 */
struct ad5421_state {
        struct spi_device               *spi;
        unsigned int                    ctrl;
        enum ad5421_current_range       current_range;
        unsigned int                    fault_mask;

        /*
         * DMA (thus cache coherency maintenance) requires the
         * transfer buffers to live in their own cache lines.
         */
        union {
                __be32 d32;
                u8 d8[4];
        } data[2] ____cacheline_aligned;
};

static const struct iio_event_spec ad5421_current_event[] = {
        {
                .type = IIO_EV_TYPE_THRESH,
                .dir = IIO_EV_DIR_RISING,
                .mask_separate = BIT(IIO_EV_INFO_VALUE) |
                        BIT(IIO_EV_INFO_ENABLE),
        }, {
                .type = IIO_EV_TYPE_THRESH,
                .dir = IIO_EV_DIR_FALLING,
                .mask_separate = BIT(IIO_EV_INFO_VALUE) |
                        BIT(IIO_EV_INFO_ENABLE),
        },
};

static const struct iio_event_spec ad5421_temp_event[] = {
        {
                .type = IIO_EV_TYPE_THRESH,
                .dir = IIO_EV_DIR_RISING,
                .mask_separate = BIT(IIO_EV_INFO_VALUE) |
                        BIT(IIO_EV_INFO_ENABLE),
        },
};

static const struct iio_chan_spec ad5421_channels[] = {
        {
                .type = IIO_CURRENT,
                .indexed = 1,
                .output = 1,
                .channel = 0,
                .info_mask_separate = BIT(IIO_CHAN_INFO_RAW) |
                        BIT(IIO_CHAN_INFO_CALIBSCALE) |
                        BIT(IIO_CHAN_INFO_CALIBBIAS),
                .info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE) |
                        BIT(IIO_CHAN_INFO_OFFSET),
                .scan_type = {
                        .sign = 'u',
                        .realbits = 16,
                        .storagebits = 16,
                },
                .event_spec = ad5421_current_event,
                .num_event_specs = ARRAY_SIZE(ad5421_current_event),
        },
        {
                .type = IIO_TEMP,
                .channel = -1,
                .event_spec = ad5421_temp_event,
                .num_event_specs = ARRAY_SIZE(ad5421_temp_event),
        },
};

static int ad5421_write_unlocked(struct iio_dev *indio_dev,
        unsigned int reg, unsigned int val)
{
        struct ad5421_state *st = iio_priv(indio_dev);

        st->data[0].d32 = cpu_to_be32((reg << 16) | val);

        return spi_write(st->spi, &st->data[0].d8[1], 3);
}

static int ad5421_write(struct iio_dev *indio_dev, unsigned int reg,
        unsigned int val)
{
        int ret;

        mutex_lock(&indio_dev->mlock);
        ret = ad5421_write_unlocked(indio_dev, reg, val);
        mutex_unlock(&indio_dev->mlock);

        return ret;
}

static int ad5421_read(struct iio_dev *indio_dev, unsigned int reg)
{
        struct ad5421_state *st = iio_priv(indio_dev);
        int ret;
        struct spi_transfer t[] = {
                {
                        .tx_buf = &st->data[0].d8[1],
                        .len = 3,
                        .cs_change = 1,
                }, {
                        .rx_buf = &st->data[1].d8[1],
                        .len = 3,
                },
        };

        mutex_lock(&indio_dev->mlock);

        st->data[0].d32 = cpu_to_be32((1 << 23) | (reg << 16));

        ret = spi_sync_transfer(st->spi, t, ARRAY_SIZE(t));
        if (ret >= 0)
                ret = be32_to_cpu(st->data[1].d32) & 0xffff;

        mutex_unlock(&indio_dev->mlock);

        return ret;
}

static int ad5421_update_ctrl(struct iio_dev *indio_dev, unsigned int set,
        unsigned int clr)
{
        struct ad5421_state *st = iio_priv(indio_dev);
        unsigned int ret;

        mutex_lock(&indio_dev->mlock);

        st->ctrl &= ~clr;
        st->ctrl |= set;

        ret = ad5421_write_unlocked(indio_dev, AD5421_REG_CTRL, st->ctrl);

        mutex_unlock(&indio_dev->mlock);

        return ret;
}

static irqreturn_t ad5421_fault_handler(int irq, void *data)
{
        struct iio_dev *indio_dev = data;
        struct ad5421_state *st = iio_priv(indio_dev);
        unsigned int fault;
        unsigned int old_fault = 0;
        unsigned int events;

        fault = ad5421_read(indio_dev, AD5421_REG_FAULT);
        if (!fault)
                return IRQ_NONE;

        /* If we had a fault, this might mean that the DAC has lost its state
         * and has been reset. Make sure that the control register actually
         * contains what we expect it to contain. Otherwise the watchdog might
         * be enabled and we get watchdog timeout faults, which will render the
         * DAC unusable. */
        ad5421_update_ctrl(indio_dev, 0, 0);


        /* The fault pin stays high as long as a fault condition is present and
         * it is not possible to mask fault conditions. For certain fault
         * conditions for example like over-temperature it takes some time
         * until the fault condition disappears. If we would exit the interrupt
         * handler immediately after handling the event it would be entered
         * again instantly. Thus we fall back to polling in case we detect that
         * a interrupt condition is still present.
         */
        do {
                /* 0xffff is a invalid value for the register and will only be
                 * read if there has been a communication error */
                if (fault == 0xffff)
                        fault = 0;

                /* we are only interested in new events */
                events = (old_fault ^ fault) & fault;
                events &= st->fault_mask;

                if (events & AD5421_FAULT_OVER_CURRENT) {
                        iio_push_event(indio_dev,
                                IIO_UNMOD_EVENT_CODE(IIO_CURRENT,
                                        0,
                                        IIO_EV_TYPE_THRESH,
                                        IIO_EV_DIR_RISING),
                        iio_get_time_ns(indio_dev));
                }

                if (events & AD5421_FAULT_UNDER_CURRENT) {
                        iio_push_event(indio_dev,
                                IIO_UNMOD_EVENT_CODE(IIO_CURRENT,
                                        0,
                                        IIO_EV_TYPE_THRESH,
                                        IIO_EV_DIR_FALLING),
                                iio_get_time_ns(indio_dev));
                }

                if (events & AD5421_FAULT_TEMP_OVER_140) {
                        iio_push_event(indio_dev,
                                IIO_UNMOD_EVENT_CODE(IIO_TEMP,
                                        0,
                                        IIO_EV_TYPE_MAG,
                                        IIO_EV_DIR_RISING),
                                iio_get_time_ns(indio_dev));
                }

                old_fault = fault;
                fault = ad5421_read(indio_dev, AD5421_REG_FAULT);

                /* still active? go to sleep for some time */
                if (fault & AD5421_FAULT_TRIGGER_IRQ)
                        msleep(1000);

        } while (fault & AD5421_FAULT_TRIGGER_IRQ);


        return IRQ_HANDLED;
}

static void ad5421_get_current_min_max(struct ad5421_state *st,
        unsigned int *min, unsigned int *max)
{
        /* The current range is configured using external pins, which are
         * usually hard-wired and not run-time switchable. */
        switch (st->current_range) {
        case AD5421_CURRENT_RANGE_4mA_20mA:
                *min = 4000;
                *max = 20000;
                break;
        case AD5421_CURRENT_RANGE_3mA8_21mA:
                *min = 3800;
                *max = 21000;
                break;
        case AD5421_CURRENT_RANGE_3mA2_24mA:
                *min = 3200;
                *max = 24000;
                break;
        default:
                *min = 0;
                *max = 1;
                break;
        }
}

static inline unsigned int ad5421_get_offset(struct ad5421_state *st)
{
        unsigned int min, max;

        ad5421_get_current_min_max(st, &min, &max);
        return (min * (1 << 16)) / (max - min);
}

static int ad5421_read_raw(struct iio_dev *indio_dev,
        struct iio_chan_spec const *chan, int *val, int *val2, long m)
{
        struct ad5421_state *st = iio_priv(indio_dev);
        unsigned int min, max;
        int ret;

        if (chan->type != IIO_CURRENT)
                return -EINVAL;

        switch (m) {
        case IIO_CHAN_INFO_RAW:
                ret = ad5421_read(indio_dev, AD5421_REG_DAC_DATA);
                if (ret < 0)
                        return ret;
                *val = ret;
                return IIO_VAL_INT;
        case IIO_CHAN_INFO_SCALE:
                ad5421_get_current_min_max(st, &min, &max);
                *val = max - min;
                *val2 = (1 << 16) * 1000;
                return IIO_VAL_FRACTIONAL;
        case IIO_CHAN_INFO_OFFSET:
                *val = ad5421_get_offset(st);
                return IIO_VAL_INT;
        case IIO_CHAN_INFO_CALIBBIAS:
                ret = ad5421_read(indio_dev, AD5421_REG_OFFSET);
                if (ret < 0)
                        return ret;
                *val = ret - 32768;
                return IIO_VAL_INT;
        case IIO_CHAN_INFO_CALIBSCALE:
                ret = ad5421_read(indio_dev, AD5421_REG_GAIN);
                if (ret < 0)
                        return ret;
                *val = ret;
                return IIO_VAL_INT;
        }

        return -EINVAL;
}

static int ad5421_write_raw(struct iio_dev *indio_dev,
        struct iio_chan_spec const *chan, int val, int val2, long mask)
{
        const unsigned int max_val = 1 << 16;

        switch (mask) {
        case IIO_CHAN_INFO_RAW:
                if (val >= max_val || val < 0)
                        return -EINVAL;

                return ad5421_write(indio_dev, AD5421_REG_DAC_DATA, val);
        case IIO_CHAN_INFO_CALIBBIAS:
                val += 32768;
                if (val >= max_val || val < 0)
                        return -EINVAL;

                return ad5421_write(indio_dev, AD5421_REG_OFFSET, val);
        case IIO_CHAN_INFO_CALIBSCALE:
                if (val >= max_val || val < 0)
                        return -EINVAL;

                return ad5421_write(indio_dev, AD5421_REG_GAIN, val);
        default:
                break;
        }

        return -EINVAL;
}

static int ad5421_write_event_config(struct iio_dev *indio_dev,
        const struct iio_chan_spec *chan, enum iio_event_type type,
        enum iio_event_direction dir, int state)
{
        struct ad5421_state *st = iio_priv(indio_dev);
        unsigned int mask;

        switch (chan->type) {
        case IIO_CURRENT:
                if (dir == IIO_EV_DIR_RISING)
                        mask = AD5421_FAULT_OVER_CURRENT;
                else
                        mask = AD5421_FAULT_UNDER_CURRENT;
                break;
        case IIO_TEMP:
                mask = AD5421_FAULT_TEMP_OVER_140;
                break;
        default:
                return -EINVAL;
        }

        mutex_lock(&indio_dev->mlock);
        if (state)
                st->fault_mask |= mask;
        else
                st->fault_mask &= ~mask;
        mutex_unlock(&indio_dev->mlock);

        return 0;
}

static int ad5421_read_event_config(struct iio_dev *indio_dev,
        const struct iio_chan_spec *chan, enum iio_event_type type,
        enum iio_event_direction dir)
{
        struct ad5421_state *st = iio_priv(indio_dev);
        unsigned int mask;

        switch (chan->type) {
        case IIO_CURRENT:
                if (dir == IIO_EV_DIR_RISING)
                        mask = AD5421_FAULT_OVER_CURRENT;
                else
                        mask = AD5421_FAULT_UNDER_CURRENT;
                break;
        case IIO_TEMP:
                mask = AD5421_FAULT_TEMP_OVER_140;
                break;
        default:
                return -EINVAL;
        }

        return (bool)(st->fault_mask & mask);
}

static int ad5421_read_event_value(struct iio_dev *indio_dev,
        const struct iio_chan_spec *chan, enum iio_event_type type,
        enum iio_event_direction dir, enum iio_event_info info, int *val,
        int *val2)
{
        int ret;

        switch (chan->type) {
        case IIO_CURRENT:
                ret = ad5421_read(indio_dev, AD5421_REG_DAC_DATA);
                if (ret < 0)
                        return ret;
                *val = ret;
                break;
        case IIO_TEMP:
                *val = 140000;
                break;
        default:
                return -EINVAL;
        }

        return IIO_VAL_INT;
}

static const struct iio_info ad5421_info = {
        .read_raw =             ad5421_read_raw,
        .write_raw =            ad5421_write_raw,
        .read_event_config =    ad5421_read_event_config,
        .write_event_config =   ad5421_write_event_config,
        .read_event_value =     ad5421_read_event_value,
};

static int ad5421_probe(struct spi_device *spi)
{
        struct ad5421_platform_data *pdata = dev_get_platdata(&spi->dev);
        struct iio_dev *indio_dev;
        struct ad5421_state *st;
        int ret;

        indio_dev = devm_iio_device_alloc(&spi->dev, sizeof(*st));
        if (indio_dev == NULL) {
                dev_err(&spi->dev, "Failed to allocate iio device\n");
                return  -ENOMEM;
        }

        st = iio_priv(indio_dev);
        spi_set_drvdata(spi, indio_dev);

        st->spi = spi;

        indio_dev->dev.parent = &spi->dev;
        indio_dev->name = "ad5421";
        indio_dev->info = &ad5421_info;
        indio_dev->modes = INDIO_DIRECT_MODE;
        indio_dev->channels = ad5421_channels;
        indio_dev->num_channels = ARRAY_SIZE(ad5421_channels);

        st->ctrl = AD5421_CTRL_WATCHDOG_DISABLE |
                        AD5421_CTRL_AUTO_FAULT_READBACK;

        if (pdata) {
                st->current_range = pdata->current_range;
                if (pdata->external_vref)
                        st->ctrl |= AD5421_CTRL_PWR_DOWN_INT_VREF;
        } else {
                st->current_range = AD5421_CURRENT_RANGE_4mA_20mA;
        }

        /* write initial ctrl register value */
        ad5421_update_ctrl(indio_dev, 0, 0);

        if (spi->irq) {
                ret = devm_request_threaded_irq(&spi->dev, spi->irq,
                                           NULL,
                                           ad5421_fault_handler,
                                           IRQF_TRIGGER_HIGH | IRQF_ONESHOT,
                                           "ad5421 fault",
                                           indio_dev);
                if (ret)
                        return ret;
        }

        return devm_iio_device_register(&spi->dev, indio_dev);
}

static struct spi_driver ad5421_driver = {
        .driver = {
                   .name = "ad5421",
        },
        .probe = ad5421_probe,
};
module_spi_driver(ad5421_driver);

MODULE_AUTHOR("Lars-Peter Clausen <lars@metafoo.de>");
MODULE_DESCRIPTION("Analog Devices AD5421 DAC");
MODULE_LICENSE("GPL v2");
MODULE_ALIAS("spi:ad5421");