/*
 * 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/err.h>
#include <linux/slab.h>
#include <linux/i2c.h>
#include <linux/hwmon.h>
#include <linux/hwmon-sysfs.h>

/* Valid addresses are 0x20 - 0x3f
 *
 * For now, we do not probe, since some of these addresses
 * are known to be unfriendly to probing */
static const unsigned short normal_i2c[] = { I2C_CLIENT_END };

/* Insmod parameters */
I2C_CLIENT_INSMOD_1(ltc4245);

/* 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_GPIOADC1                = 0x1c,
        LTC4245_GPIOADC2                = 0x1d,
        LTC4245_GPIOADC3                = 0x1e,
};

struct ltc4245_data {
        struct device *hwmon_dev;

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

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

        /* Voltage registers */
        u8 vregs[0x0f];
};

static struct ltc4245_data *ltc4245_update_device(struct device *dev)
{
        struct i2c_client *client = to_i2c_client(dev);
        struct ltc4245_data *data = i2c_get_clientdata(client);
        s32 val;
        int i;

        mutex_lock(&data->update_lock);

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

                dev_dbg(&client->dev, "Starting ltc4245 update\n");

                /* 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 0x1f */
                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;
                }

                data->last_updated = jiffies;
                data->valid = 1;
        }

        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_GPIOADC1:
        case LTC4245_GPIOADC2:
        case LTC4245_GPIOADC3:
                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;
}

static ssize_t ltc4245_show_voltage(struct device *dev,
                                    struct device_attribute *da,
                                    char *buf)
{
        struct sensor_device_attribute *attr = to_sensor_dev_attr(da);
        const int voltage = ltc4245_get_voltage(dev, attr->index);

        return snprintf(buf, PAGE_SIZE, "%d\n", voltage);
}

static ssize_t ltc4245_show_current(struct device *dev,
                                    struct device_attribute *da,
                                    char *buf)
{
        struct sensor_device_attribute *attr = to_sensor_dev_attr(da);
        const unsigned int curr = ltc4245_get_current(dev, attr->index);

        return snprintf(buf, PAGE_SIZE, "%u\n", curr);
}

static ssize_t ltc4245_show_power(struct device *dev,
                                  struct device_attribute *da,
                                  char *buf)
{
        struct sensor_device_attribute *attr = to_sensor_dev_attr(da);
        const unsigned int curr = ltc4245_get_current(dev, attr->index);
        const int output_voltage = ltc4245_get_voltage(dev, attr->index+1);

        /* current in mA * voltage in mV == power in uW */
        const unsigned int power = abs(output_voltage * curr);

        return snprintf(buf, PAGE_SIZE, "%u\n", power);
}

static ssize_t ltc4245_show_alarm(struct device *dev,
                                          struct device_attribute *da,
                                          char *buf)
{
        struct sensor_device_attribute_2 *attr = to_sensor_dev_attr_2(da);
        struct ltc4245_data *data = ltc4245_update_device(dev);
        const u8 reg = data->cregs[attr->index];
        const u32 mask = attr->nr;

        return snprintf(buf, PAGE_SIZE, "%u\n", (reg & mask) ? 1 : 0);
}

/* These macros are used below in constructing device attribute objects
 * for use with sysfs_create_group() to make a sysfs device file
 * for each register.
 */

#define LTC4245_VOLTAGE(name, ltc4245_cmd_idx) \
        static SENSOR_DEVICE_ATTR(name, S_IRUGO, \
        ltc4245_show_voltage, NULL, ltc4245_cmd_idx)

#define LTC4245_CURRENT(name, ltc4245_cmd_idx) \
        static SENSOR_DEVICE_ATTR(name, S_IRUGO, \
        ltc4245_show_current, NULL, ltc4245_cmd_idx)

#define LTC4245_POWER(name, ltc4245_cmd_idx) \
        static SENSOR_DEVICE_ATTR(name, S_IRUGO, \
        ltc4245_show_power, NULL, ltc4245_cmd_idx)

#define LTC4245_ALARM(name, mask, reg) \
        static SENSOR_DEVICE_ATTR_2(name, S_IRUGO, \
        ltc4245_show_alarm, NULL, (mask), reg)

/* Construct a sensor_device_attribute structure for each register */

/* Input voltages */
LTC4245_VOLTAGE(in1_input,                      LTC4245_12VIN);
LTC4245_VOLTAGE(in2_input,                      LTC4245_5VIN);
LTC4245_VOLTAGE(in3_input,                      LTC4245_3VIN);
LTC4245_VOLTAGE(in4_input,                      LTC4245_VEEIN);

/* Input undervoltage alarms */
LTC4245_ALARM(in1_min_alarm,    (1 << 0),       LTC4245_FAULT1);
LTC4245_ALARM(in2_min_alarm,    (1 << 1),       LTC4245_FAULT1);
LTC4245_ALARM(in3_min_alarm,    (1 << 2),       LTC4245_FAULT1);
LTC4245_ALARM(in4_min_alarm,    (1 << 3),       LTC4245_FAULT1);

/* Currents (via sense resistor) */
LTC4245_CURRENT(curr1_input,                    LTC4245_12VSENSE);
LTC4245_CURRENT(curr2_input,                    LTC4245_5VSENSE);
LTC4245_CURRENT(curr3_input,                    LTC4245_3VSENSE);
LTC4245_CURRENT(curr4_input,                    LTC4245_VEESENSE);

/* Overcurrent alarms */
LTC4245_ALARM(curr1_max_alarm,  (1 << 4),       LTC4245_FAULT1);
LTC4245_ALARM(curr2_max_alarm,  (1 << 5),       LTC4245_FAULT1);
LTC4245_ALARM(curr3_max_alarm,  (1 << 6),       LTC4245_FAULT1);
LTC4245_ALARM(curr4_max_alarm,  (1 << 7),       LTC4245_FAULT1);

/* Output voltages */
LTC4245_VOLTAGE(in5_input,                      LTC4245_12VOUT);
LTC4245_VOLTAGE(in6_input,                      LTC4245_5VOUT);
LTC4245_VOLTAGE(in7_input,                      LTC4245_3VOUT);
LTC4245_VOLTAGE(in8_input,                      LTC4245_VEEOUT);

/* Power Bad alarms */
LTC4245_ALARM(in5_min_alarm,    (1 << 0),       LTC4245_FAULT2);
LTC4245_ALARM(in6_min_alarm,    (1 << 1),       LTC4245_FAULT2);
LTC4245_ALARM(in7_min_alarm,    (1 << 2),       LTC4245_FAULT2);
LTC4245_ALARM(in8_min_alarm,    (1 << 3),       LTC4245_FAULT2);

/* GPIO voltages */
LTC4245_VOLTAGE(in9_input,                      LTC4245_GPIOADC1);
LTC4245_VOLTAGE(in10_input,                     LTC4245_GPIOADC2);
LTC4245_VOLTAGE(in11_input,                     LTC4245_GPIOADC3);

/* Power Consumption (virtual) */
LTC4245_POWER(power1_input,                     LTC4245_12VSENSE);
LTC4245_POWER(power2_input,                     LTC4245_5VSENSE);
LTC4245_POWER(power3_input,                     LTC4245_3VSENSE);
LTC4245_POWER(power4_input,                     LTC4245_VEESENSE);

/* Finally, construct an array of pointers to members of the above objects,
 * as required for sysfs_create_group()
 */
static struct attribute *ltc4245_attributes[] = {
        &sensor_dev_attr_in1_input.dev_attr.attr,
        &sensor_dev_attr_in2_input.dev_attr.attr,
        &sensor_dev_attr_in3_input.dev_attr.attr,
        &sensor_dev_attr_in4_input.dev_attr.attr,

        &sensor_dev_attr_in1_min_alarm.dev_attr.attr,
        &sensor_dev_attr_in2_min_alarm.dev_attr.attr,
        &sensor_dev_attr_in3_min_alarm.dev_attr.attr,
        &sensor_dev_attr_in4_min_alarm.dev_attr.attr,

        &sensor_dev_attr_curr1_input.dev_attr.attr,
        &sensor_dev_attr_curr2_input.dev_attr.attr,
        &sensor_dev_attr_curr3_input.dev_attr.attr,
        &sensor_dev_attr_curr4_input.dev_attr.attr,

        &sensor_dev_attr_curr1_max_alarm.dev_attr.attr,
        &sensor_dev_attr_curr2_max_alarm.dev_attr.attr,
        &sensor_dev_attr_curr3_max_alarm.dev_attr.attr,
        &sensor_dev_attr_curr4_max_alarm.dev_attr.attr,

        &sensor_dev_attr_in5_input.dev_attr.attr,
        &sensor_dev_attr_in6_input.dev_attr.attr,
        &sensor_dev_attr_in7_input.dev_attr.attr,
        &sensor_dev_attr_in8_input.dev_attr.attr,

        &sensor_dev_attr_in5_min_alarm.dev_attr.attr,
        &sensor_dev_attr_in6_min_alarm.dev_attr.attr,
        &sensor_dev_attr_in7_min_alarm.dev_attr.attr,
        &sensor_dev_attr_in8_min_alarm.dev_attr.attr,

        &sensor_dev_attr_in9_input.dev_attr.attr,
        &sensor_dev_attr_in10_input.dev_attr.attr,
        &sensor_dev_attr_in11_input.dev_attr.attr,

        &sensor_dev_attr_power1_input.dev_attr.attr,
        &sensor_dev_attr_power2_input.dev_attr.attr,
        &sensor_dev_attr_power3_input.dev_attr.attr,
        &sensor_dev_attr_power4_input.dev_attr.attr,

        NULL,
};

static const struct attribute_group ltc4245_group = {
        .attrs = ltc4245_attributes,
};

static int ltc4245_probe(struct i2c_client *client,
                         const struct i2c_device_id *id)
{
        struct ltc4245_data *data;
        int ret;

        data = kzalloc(sizeof(*data), GFP_KERNEL);
        if (!data) {
                ret = -ENOMEM;
                goto out_kzalloc;
        }

        i2c_set_clientdata(client, data);
        mutex_init(&data->update_lock);

        /* Initialize the LTC4245 chip */
        /* TODO */

        /* Register sysfs hooks */
        ret = sysfs_create_group(&client->dev.kobj, &ltc4245_group);
        if (ret)
                goto out_sysfs_create_group;

        data->hwmon_dev = hwmon_device_register(&client->dev);
        if (IS_ERR(data->hwmon_dev)) {
                ret = PTR_ERR(data->hwmon_dev);
                goto out_hwmon_device_register;
        }

        return 0;

out_hwmon_device_register:
        sysfs_remove_group(&client->dev.kobj, &ltc4245_group);
out_sysfs_create_group:
        kfree(data);
out_kzalloc:
        return ret;
}

static int ltc4245_remove(struct i2c_client *client)
{
        struct ltc4245_data *data = i2c_get_clientdata(client);

        hwmon_device_unregister(data->hwmon_dev);
        sysfs_remove_group(&client->dev.kobj, &ltc4245_group);

        kfree(data);

        return 0;
}

/* Check that some bits in a control register appear at all possible
 * locations without changing value
 *
 * @client: the i2c client to use
 * @reg: the register to read
 * @bits: the bits to check (0xff checks all bits,
 *                           0x03 checks only the last two bits)
 *
 * return -ERRNO if the register read failed
 * return -ENODEV if the register value doesn't stay constant at all
 * possible addresses
 *
 * return 0 for success
 */
static int ltc4245_check_control_reg(struct i2c_client *client, u8 reg, u8 bits)
{
        int i;
        s32 v, voff1, voff2;

        /* Read register and check for error */
        v = i2c_smbus_read_byte_data(client, reg);
        if (v < 0)
                return v;

        v &= bits;

        for (i = 0x00; i < 0xff; i += 0x20) {

                voff1 = i2c_smbus_read_byte_data(client, reg + i);
                if (voff1 < 0)
                        return voff1;

                voff2 = i2c_smbus_read_byte_data(client, reg + i + 0x08);
                if (voff2 < 0)
                        return voff2;

                voff1 &= bits;
                voff2 &= bits;

                if (v != voff1 || v != voff2)
                        return -ENODEV;
        }

        return 0;
}

static int ltc4245_detect(struct i2c_client *client,
                          int kind,
                          struct i2c_board_info *info)
{
        struct i2c_adapter *adapter = client->adapter;

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

        if (kind < 0) {         /* probed detection - check the chip type */
                s32 v;          /* 8 bits from the chip, or -ERRNO */

                /* Chip registers 0x00-0x07 are control registers
                 * Chip registers 0x10-0x1f are data registers
                 *
                 * Address bits b7-b5 are ignored. This makes the chip "repeat"
                 * in steps of 0x20. Any control registers should appear with
                 * the same values across all duplicated addresses.
                 *
                 * Register 0x02 bit b2 is reserved, expect 0
                 * Register 0x07 bits b7 to b4 are reserved, expect 0
                 *
                 * Registers 0x01, 0x02 are control registers and should not
                 * change on their own.
                 *
                 * Register 0x06 bits b6 and b7 are control bits, and should
                 * not change on their own.
                 *
                 * Register 0x07 bits b3 to b0 are control bits, and should
                 * not change on their own.
                 */

                /* read register 0x02 reserved bit, expect 0 */
                v = i2c_smbus_read_byte_data(client, LTC4245_CONTROL);
                if (v < 0 || (v & 0x04) != 0)
                        return -ENODEV;

                /* read register 0x07 reserved bits, expect 0 */
                v = i2c_smbus_read_byte_data(client, LTC4245_ADCADR);
                if (v < 0 || (v & 0xf0) != 0)
                        return -ENODEV;

                /* check that the alert register appears at all locations */
                if (ltc4245_check_control_reg(client, LTC4245_ALERT, 0xff))
                        return -ENODEV;

                /* check that the control register appears at all locations */
                if (ltc4245_check_control_reg(client, LTC4245_CONTROL, 0xff))
                        return -ENODEV;

                /* check that register 0x06 bits b6 and b7 stay constant */
                if (ltc4245_check_control_reg(client, LTC4245_GPIO, 0xc0))
                        return -ENODEV;

                /* check that register 0x07 bits b3-b0 stay constant */
                if (ltc4245_check_control_reg(client, LTC4245_ADCADR, 0x0f))
                        return -ENODEV;
        }

        strlcpy(info->type, "ltc4245", I2C_NAME_SIZE);
        dev_info(&adapter->dev, "ltc4245 %s at address 0x%02x\n",
                        kind < 0 ? "probed" : "forced",
                        client->addr);

        return 0;
}

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

/* This is the driver that will be inserted */
static struct i2c_driver ltc4245_driver = {
        .class          = I2C_CLASS_HWMON,
        .driver = {
                .name   = "ltc4245",
        },
        .probe          = ltc4245_probe,
        .remove         = ltc4245_remove,
        .id_table       = ltc4245_id,
        .detect         = ltc4245_detect,
        .address_data   = &addr_data,
};

static int __init ltc4245_init(void)
{
        return i2c_add_driver(&ltc4245_driver);
}

static void __exit ltc4245_exit(void)
{
        i2c_del_driver(&ltc4245_driver);
}

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

module_init(ltc4245_init);
module_exit(ltc4245_exit);