/*
 * Driver for Linear Technology LTC4245 I2C Multiple Supply Hot Swap Controller
 *
 * Copyright (C) 2008 Ira W. Snyder <iws@ovro.caltech.edu>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; version 2 of the License.
 *
 * This driver is based on the ds1621 and ina209 drivers.
 *
 * Datasheet:
 * http://www.linear.com/pc/downloadDocument.do?navId=H0,C1,C1003,C1006,C1140,P19392,D13517
 */

#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/init.h>
#include <linux/bitops.h>
#include <linux/err.h>
#include <linux/slab.h>
#include <linux/i2c.h>
#include <linux/hwmon.h>
#include <linux/hwmon-sysfs.h>
#include <linux/jiffies.h>
#include <linux/platform_data/ltc4245.h>

/* Here are names of the chip's registers (a.k.a. commands) */
enum ltc4245_cmd {
        LTC4245_STATUS                  = 0x00, /* readonly */
        LTC4245_ALERT                   = 0x01,
        LTC4245_CONTROL                 = 0x02,
        LTC4245_ON                      = 0x03,
        LTC4245_FAULT1                  = 0x04,
        LTC4245_FAULT2                  = 0x05,
        LTC4245_GPIO                    = 0x06,
        LTC4245_ADCADR                  = 0x07,

        LTC4245_12VIN                   = 0x10,
        LTC4245_12VSENSE                = 0x11,
        LTC4245_12VOUT                  = 0x12,
        LTC4245_5VIN                    = 0x13,
        LTC4245_5VSENSE                 = 0x14,
        LTC4245_5VOUT                   = 0x15,
        LTC4245_3VIN                    = 0x16,
        LTC4245_3VSENSE                 = 0x17,
        LTC4245_3VOUT                   = 0x18,
        LTC4245_VEEIN                   = 0x19,
        LTC4245_VEESENSE                = 0x1a,
        LTC4245_VEEOUT                  = 0x1b,
        LTC4245_GPIOADC                 = 0x1c,
};

struct ltc4245_data {
        struct i2c_client *client;

        struct mutex update_lock;
        bool valid;
        unsigned long last_updated; /* in jiffies */

        /* Control registers */
        u8 cregs[0x08];

        /* Voltage registers */
        u8 vregs[0x0d];

        /* GPIO ADC registers */
        bool use_extra_gpios;
        int gpios[3];
};

/*
 * Update the readings from the GPIO pins. If the driver has been configured to
 * sample all GPIO's as analog voltages, a round-robin sampling method is used.
 * Otherwise, only the configured GPIO pin is sampled.
 *
 * LOCKING: must hold data->update_lock
 */
static void ltc4245_update_gpios(struct device *dev)
{
        struct ltc4245_data *data = dev_get_drvdata(dev);
        struct i2c_client *client = data->client;
        u8 gpio_curr, gpio_next, gpio_reg;
        int i;

        /* no extra gpio support, we're basically done */
        if (!data->use_extra_gpios) {
                data->gpios[0] = data->vregs[LTC4245_GPIOADC - 0x10];
                return;
        }

        /*
         * If the last reading was too long ago, then we mark all old GPIO
         * readings as stale by setting them to -EAGAIN
         */
        if (time_after(jiffies, data->last_updated + 5 * HZ)) {
                for (i = 0; i < ARRAY_SIZE(data->gpios); i++)
                        data->gpios[i] = -EAGAIN;
        }

        /*
         * Get the current GPIO pin
         *
         * The datasheet calls these GPIO[1-3], but we'll calculate the zero
         * based array index instead, and call them GPIO[0-2]. This is much
         * easier to think about.
         */
        gpio_curr = (data->cregs[LTC4245_GPIO] & 0xc0) >> 6;
        if (gpio_curr > 0)
                gpio_curr -= 1;

        /* Read the GPIO voltage from the GPIOADC register */
        data->gpios[gpio_curr] = data->vregs[LTC4245_GPIOADC - 0x10];

        /* Find the next GPIO pin to read */
        gpio_next = (gpio_curr + 1) % ARRAY_SIZE(data->gpios);

        /*
         * Calculate the correct setting for the GPIO register so it will
         * sample the next GPIO pin
         */
        gpio_reg = (data->cregs[LTC4245_GPIO] & 0x3f) | ((gpio_next + 1) << 6);

        /* Update the GPIO register */
        i2c_smbus_write_byte_data(client, LTC4245_GPIO, gpio_reg);

        /* Update saved data */
        data->cregs[LTC4245_GPIO] = gpio_reg;
}

static struct ltc4245_data *ltc4245_update_device(struct device *dev)
{
        struct ltc4245_data *data = dev_get_drvdata(dev);
        struct i2c_client *client = data->client;
        s32 val;
        int i;

        mutex_lock(&data->update_lock);

        if (time_after(jiffies, data->last_updated + HZ) || !data->valid) {

                /* Read control registers -- 0x00 to 0x07 */
                for (i = 0; i < ARRAY_SIZE(data->cregs); i++) {
                        val = i2c_smbus_read_byte_data(client, i);
                        if (unlikely(val < 0))
                                data->cregs[i] = 0;
                        else
                                data->cregs[i] = val;
                }

                /* Read voltage registers -- 0x10 to 0x1c */
                for (i = 0; i < ARRAY_SIZE(data->vregs); i++) {
                        val = i2c_smbus_read_byte_data(client, i+0x10);
                        if (unlikely(val < 0))
                                data->vregs[i] = 0;
                        else
                                data->vregs[i] = val;
                }

                /* Update GPIO readings */
                ltc4245_update_gpios(dev);

                data->last_updated = jiffies;
                data->valid = true;
        }

        mutex_unlock(&data->update_lock);

        return data;
}

/* Return the voltage from the given register in millivolts */
static int ltc4245_get_voltage(struct device *dev, u8 reg)
{
        struct ltc4245_data *data = ltc4245_update_device(dev);
        const u8 regval = data->vregs[reg - 0x10];
        u32 voltage = 0;

        switch (reg) {
        case LTC4245_12VIN:
        case LTC4245_12VOUT:
                voltage = regval * 55;
                break;
        case LTC4245_5VIN:
        case LTC4245_5VOUT:
                voltage = regval * 22;
                break;
        case LTC4245_3VIN:
        case LTC4245_3VOUT:
                voltage = regval * 15;
                break;
        case LTC4245_VEEIN:
        case LTC4245_VEEOUT:
                voltage = regval * -55;
                break;
        case LTC4245_GPIOADC:
                voltage = regval * 10;
                break;
        default:
                /* If we get here, the developer messed up */
                WARN_ON_ONCE(1);
                break;
        }

        return voltage;
}

/* Return the current in the given sense register in milliAmperes */
static unsigned int ltc4245_get_current(struct device *dev, u8 reg)
{
        struct ltc4245_data *data = ltc4245_update_device(dev);
        const u8 regval = data->vregs[reg - 0x10];
        unsigned int voltage;
        unsigned int curr;

        /*
         * The strange looking conversions that follow are fixed-point
         * math, since we cannot do floating point in the kernel.
         *
         * Step 1: convert sense register to microVolts
         * Step 2: convert voltage to milliAmperes
         *
         * If you play around with the V=IR equation, you come up with
         * the following: X uV / Y mOhm == Z mA
         *
         * With the resistors that are fractions of a milliOhm, we multiply
         * the voltage and resistance by 10, to shift the decimal point.
         * Now we can use the normal division operator again.
         */

        switch (reg) {
        case LTC4245_12VSENSE:
                voltage = regval * 250; /* voltage in uV */
                curr = voltage / 50; /* sense resistor 50 mOhm */
                break;
        case LTC4245_5VSENSE:
                voltage = regval * 125; /* voltage in uV */
                curr = (voltage * 10) / 35; /* sense resistor 3.5 mOhm */
                break;
        case LTC4245_3VSENSE:
                voltage = regval * 125; /* voltage in uV */
                curr = (voltage * 10) / 25; /* sense resistor 2.5 mOhm */
                break;
        case LTC4245_VEESENSE:
                voltage = regval * 250; /* voltage in uV */
                curr = voltage / 100; /* sense resistor 100 mOhm */
                break;
        default:
                /* If we get here, the developer messed up */
                WARN_ON_ONCE(1);
                curr = 0;
                break;
        }

        return curr;
}

/* Map from voltage channel index to voltage register */

static const s8 ltc4245_in_regs[] = {
        LTC4245_12VIN, LTC4245_5VIN, LTC4245_3VIN, LTC4245_VEEIN,
        LTC4245_12VOUT, LTC4245_5VOUT, LTC4245_3VOUT, LTC4245_VEEOUT,
};

/* Map from current channel index to current register */

static const s8 ltc4245_curr_regs[] = {
        LTC4245_12VSENSE, LTC4245_5VSENSE, LTC4245_3VSENSE, LTC4245_VEESENSE,
};

static int ltc4245_read_curr(struct device *dev, u32 attr, int channel,
                             long *val)
{
        struct ltc4245_data *data = ltc4245_update_device(dev);

        switch (attr) {
        case hwmon_curr_input:
                *val = ltc4245_get_current(dev, ltc4245_curr_regs[channel]);
                return 0;
        case hwmon_curr_max_alarm:
                *val = !!(data->cregs[LTC4245_FAULT1] & BIT(channel + 4));
                return 0;
        default:
                return -EOPNOTSUPP;
        }
}

static int ltc4245_read_in(struct device *dev, u32 attr, int channel, long *val)
{
        struct ltc4245_data *data = ltc4245_update_device(dev);

        switch (attr) {
        case hwmon_in_input:
                if (channel < 8) {
                        *val = ltc4245_get_voltage(dev,
                                                ltc4245_in_regs[channel]);
                } else {
                        int regval = data->gpios[channel - 8];

                        if (regval < 0)
                                return regval;
                        *val = regval * 10;
                }
                return 0;
        case hwmon_in_min_alarm:
                if (channel < 4)
                        *val = !!(data->cregs[LTC4245_FAULT1] & BIT(channel));
                else
                        *val = !!(data->cregs[LTC4245_FAULT2] &
                                  BIT(channel - 4));
                return 0;
        default:
                return -EOPNOTSUPP;
        }
}

static int ltc4245_read_power(struct device *dev, u32 attr, int channel,
                              long *val)
{
        unsigned long curr;
        long voltage;

        switch (attr) {
        case hwmon_power_input:
                (void)ltc4245_update_device(dev);
                curr = ltc4245_get_current(dev, ltc4245_curr_regs[channel]);
                voltage = ltc4245_get_voltage(dev, ltc4245_in_regs[channel]);
                *val = abs(curr * voltage);
                return 0;
        default:
                return -EOPNOTSUPP;
        }
}

static int ltc4245_read(struct device *dev, enum hwmon_sensor_types type,
                        u32 attr, int channel, long *val)
{

        switch (type) {
        case hwmon_curr:
                return ltc4245_read_curr(dev, attr, channel, val);
        case hwmon_power:
                return ltc4245_read_power(dev, attr, channel, val);
        case hwmon_in:
                return ltc4245_read_in(dev, attr, channel - 1, val);
        default:
                return -EOPNOTSUPP;
        }
}

static umode_t ltc4245_is_visible(const void *_data,
                                  enum hwmon_sensor_types type,
                                  u32 attr, int channel)
{
        const struct ltc4245_data *data = _data;

        switch (type) {
        case hwmon_in:
                if (channel == 0)
                        return 0;
                switch (attr) {
                case hwmon_in_input:
                        if (channel > 9 && !data->use_extra_gpios)
                                return 0;
                        return S_IRUGO;
                case hwmon_in_min_alarm:
                        if (channel > 8)
                                return 0;
                        return S_IRUGO;
                default:
                        return 0;
                }
        case hwmon_curr:
                switch (attr) {
                case hwmon_curr_input:
                case hwmon_curr_max_alarm:
                        return S_IRUGO;
                default:
                        return 0;
                }
        case hwmon_power:
                switch (attr) {
                case hwmon_power_input:
                        return S_IRUGO;
                default:
                        return 0;
                }
        default:
                return 0;
        }
}

static const u32 ltc4245_in_config[] = {
        HWMON_I_INPUT,                  /* dummy, skipped in is_visible */
        HWMON_I_INPUT | HWMON_I_MIN_ALARM,
        HWMON_I_INPUT | HWMON_I_MIN_ALARM,
        HWMON_I_INPUT | HWMON_I_MIN_ALARM,
        HWMON_I_INPUT | HWMON_I_MIN_ALARM,
        HWMON_I_INPUT | HWMON_I_MIN_ALARM,
        HWMON_I_INPUT | HWMON_I_MIN_ALARM,
        HWMON_I_INPUT | HWMON_I_MIN_ALARM,
        HWMON_I_INPUT | HWMON_I_MIN_ALARM,
        HWMON_I_INPUT,
        HWMON_I_INPUT,
        HWMON_I_INPUT,
        0
};

static const struct hwmon_channel_info ltc4245_in = {
        .type = hwmon_in,
        .config = ltc4245_in_config,
};

static const u32 ltc4245_curr_config[] = {
        HWMON_C_INPUT | HWMON_C_MAX_ALARM,
        HWMON_C_INPUT | HWMON_C_MAX_ALARM,
        HWMON_C_INPUT | HWMON_C_MAX_ALARM,
        HWMON_C_INPUT | HWMON_C_MAX_ALARM,
        0
};

static const struct hwmon_channel_info ltc4245_curr = {
        .type = hwmon_curr,
        .config = ltc4245_curr_config,
};

static const u32 ltc4245_power_config[] = {
        HWMON_P_INPUT,
        HWMON_P_INPUT,
        HWMON_P_INPUT,
        HWMON_P_INPUT,
        0
};

static const struct hwmon_channel_info ltc4245_power = {
        .type = hwmon_power,
        .config = ltc4245_power_config,
};

static const struct hwmon_channel_info *ltc4245_info[] = {
        &ltc4245_in,
        &ltc4245_curr,
        &ltc4245_power,
        NULL
};

static const struct hwmon_ops ltc4245_hwmon_ops = {
        .is_visible = ltc4245_is_visible,
        .read = ltc4245_read,
};

static const struct hwmon_chip_info ltc4245_chip_info = {
        .ops = &ltc4245_hwmon_ops,
        .info = ltc4245_info,
};

static bool ltc4245_use_extra_gpios(struct i2c_client *client)
{
        struct ltc4245_platform_data *pdata = dev_get_platdata(&client->dev);
        struct device_node *np = client->dev.of_node;

        /* prefer platform data */
        if (pdata)
                return pdata->use_extra_gpios;

        /* fallback on OF */
        if (of_find_property(np, "ltc4245,use-extra-gpios", NULL))
                return true;

        return false;
}

static int ltc4245_probe(struct i2c_client *client,
                         const struct i2c_device_id *id)
{
        struct i2c_adapter *adapter = client->adapter;
        struct ltc4245_data *data;
        struct device *hwmon_dev;

        if (!i2c_check_functionality(adapter, I2C_FUNC_SMBUS_BYTE_DATA))
                return -ENODEV;

        data = devm_kzalloc(&client->dev, sizeof(*data), GFP_KERNEL);
        if (!data)
                return -ENOMEM;

        data->client = client;
        mutex_init(&data->update_lock);
        data->use_extra_gpios = ltc4245_use_extra_gpios(client);

        /* Initialize the LTC4245 chip */
        i2c_smbus_write_byte_data(client, LTC4245_FAULT1, 0x00);
        i2c_smbus_write_byte_data(client, LTC4245_FAULT2, 0x00);

        hwmon_dev = devm_hwmon_device_register_with_info(&client->dev,
                                                         client->name, data,
                                                         &ltc4245_chip_info,
                                                         NULL);
        return PTR_ERR_OR_ZERO(hwmon_dev);
}

static const struct i2c_device_id ltc4245_id[] = {
        { "ltc4245", 0 },
        { }
};
MODULE_DEVICE_TABLE(i2c, ltc4245_id);

/* This is the driver that will be inserted */
static struct i2c_driver ltc4245_driver = {
        .driver = {
                .name   = "ltc4245",
        },
        .probe          = ltc4245_probe,
        .id_table       = ltc4245_id,
};

module_i2c_driver(ltc4245_driver);

MODULE_AUTHOR("Ira W. Snyder <iws@ovro.caltech.edu>");
MODULE_DESCRIPTION("LTC4245 driver");
MODULE_LICENSE("GPL");