/*
 * tc654.c - Linux kernel modules for fan speed controller
 *
 * Copyright (C) 2016 Allied Telesis Labs NZ
 *
 * 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; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 */

#include <linux/bitops.h>
#include <linux/err.h>
#include <linux/hwmon.h>
#include <linux/hwmon-sysfs.h>
#include <linux/i2c.h>
#include <linux/init.h>
#include <linux/jiffies.h>
#include <linux/module.h>
#include <linux/mutex.h>
#include <linux/slab.h>
#include <linux/util_macros.h>

enum tc654_regs {
        TC654_REG_RPM1 = 0x00,  /* RPM Output 1 */
        TC654_REG_RPM2 = 0x01,  /* RPM Output 2 */
        TC654_REG_FAN_FAULT1 = 0x02,    /* Fan Fault 1 Threshold */
        TC654_REG_FAN_FAULT2 = 0x03,    /* Fan Fault 2 Threshold */
        TC654_REG_CONFIG = 0x04,        /* Configuration */
        TC654_REG_STATUS = 0x05,        /* Status */
        TC654_REG_DUTY_CYCLE = 0x06,    /* Fan Speed Duty Cycle */
        TC654_REG_MFR_ID = 0x07,        /* Manufacturer Identification */
        TC654_REG_VER_ID = 0x08,        /* Version Identification */
};

/* Macros to easily index the registers */
#define TC654_REG_RPM(idx)              (TC654_REG_RPM1 + (idx))
#define TC654_REG_FAN_FAULT(idx)        (TC654_REG_FAN_FAULT1 + (idx))

/* Config register bits */
#define TC654_REG_CONFIG_RES            BIT(6)  /* Resolution Selection */
#define TC654_REG_CONFIG_DUTYC          BIT(5)  /* Duty Cycle Control */
#define TC654_REG_CONFIG_SDM            BIT(0)  /* Shutdown Mode */

/* Status register bits */
#define TC654_REG_STATUS_F2F            BIT(1)  /* Fan 2 Fault */
#define TC654_REG_STATUS_F1F            BIT(0)  /* Fan 1 Fault */

/* RPM resolution for RPM Output registers */
#define TC654_HIGH_RPM_RESOLUTION       25      /* 25 RPM resolution */
#define TC654_LOW_RPM_RESOLUTION        50      /* 50 RPM resolution */

/* Convert to the fan fault RPM threshold from register value */
#define TC654_FAN_FAULT_FROM_REG(val)   ((val) * 50)    /* 50 RPM resolution */

/* Convert to register value from the fan fault RPM threshold */
#define TC654_FAN_FAULT_TO_REG(val)     (((val) / 50) & 0xff)

/* Register data is read (and cached) at most once per second. */
#define TC654_UPDATE_INTERVAL           HZ

struct tc654_data {
        struct i2c_client *client;

        /* update mutex */
        struct mutex update_lock;

        /* tc654 register cache */
        bool valid;
        unsigned long last_updated;     /* in jiffies */

        u8 rpm_output[2];       /* The fan RPM data for fans 1 and 2 is then
                                 * written to registers RPM1 and RPM2
                                 */
        u8 fan_fault[2];        /* The Fan Fault Threshold Registers are used to
                                 * set the fan fault threshold levels for fan 1
                                 * and fan 2
                                 */
        u8 config;      /* The Configuration Register is an 8-bit read/
                         * writable multi-function control register
                         *   7: Fan Fault Clear
                         *      1 = Clear Fan Fault
                         *      0 = Normal Operation (default)
                         *   6: Resolution Selection for RPM Output Registers
                         *      RPM Output Registers (RPM1 and RPM2) will be
                         *      set for
                         *      1 = 25 RPM (9-bit) resolution
                         *      0 = 50 RPM (8-bit) resolution (default)
                         *   5: Duty Cycle Control Method
                         *      The V OUT duty cycle will be controlled via
                         *      1 = the SMBus interface.
                         *      0 = via the V IN analog input pin. (default)
                         * 4,3: Fan 2 Pulses Per Rotation
                         *      00 = 1
                         *      01 = 2 (default)
                         *      10 = 4
                         *      11 = 8
                         * 2,1: Fan 1 Pulses Per Rotation
                         *      00 = 1
                         *      01 = 2 (default)
                         *      10 = 4
                         *      11 = 8
                         *   0: Shutdown Mode
                         *      1 = Shutdown mode.
                         *      0 = Normal operation. (default)
                         */
        u8 status;      /* The Status register provides all the information
                         * about what is going on within the TC654/TC655
                         * devices.
                         * 7,6: Unimplemented, Read as '0'
                         *   5: Over-Temperature Fault Condition
                         *      1 = Over-Temperature condition has occurred
                         *      0 = Normal operation. V IN is less than 2.6V
                         *   4: RPM2 Counter Overflow
                         *      1 = Fault condition
                         *      0 = Normal operation
                         *   3: RPM1 Counter Overflow
                         *      1 = Fault condition
                         *      0 = Normal operation
                         *   2: V IN Input Status
                         *      1 = V IN is open
                         *      0 = Normal operation. voltage present at V IN
                         *   1: Fan 2 Fault
                         *      1 = Fault condition
                         *      0 = Normal operation
                         *   0: Fan 1 Fault
                         *      1 = Fault condition
                         *      0 = Normal operation
                         */
        u8 duty_cycle;  /* The DUTY_CYCLE register is a 4-bit read/
                         * writable register used to control the duty
                         * cycle of the V OUT output.
                         */
};

/* helper to grab and cache data, at most one time per second */
static struct tc654_data *tc654_update_client(struct device *dev)
{
        struct tc654_data *data = dev_get_drvdata(dev);
        struct i2c_client *client = data->client;
        int ret = 0;

        mutex_lock(&data->update_lock);
        if (time_before(jiffies, data->last_updated + TC654_UPDATE_INTERVAL) &&
            likely(data->valid))
                goto out;

        ret = i2c_smbus_read_byte_data(client, TC654_REG_RPM(0));
        if (ret < 0)
                goto out;
        data->rpm_output[0] = ret;

        ret = i2c_smbus_read_byte_data(client, TC654_REG_RPM(1));
        if (ret < 0)
                goto out;
        data->rpm_output[1] = ret;

        ret = i2c_smbus_read_byte_data(client, TC654_REG_FAN_FAULT(0));
        if (ret < 0)
                goto out;
        data->fan_fault[0] = ret;

        ret = i2c_smbus_read_byte_data(client, TC654_REG_FAN_FAULT(1));
        if (ret < 0)
                goto out;
        data->fan_fault[1] = ret;

        ret = i2c_smbus_read_byte_data(client, TC654_REG_CONFIG);
        if (ret < 0)
                goto out;
        data->config = ret;

        ret = i2c_smbus_read_byte_data(client, TC654_REG_STATUS);
        if (ret < 0)
                goto out;
        data->status = ret;

        ret = i2c_smbus_read_byte_data(client, TC654_REG_DUTY_CYCLE);
        if (ret < 0)
                goto out;
        data->duty_cycle = ret & 0x0f;

        data->last_updated = jiffies;
        data->valid = true;
out:
        mutex_unlock(&data->update_lock);

        if (ret < 0)            /* upon error, encode it in return value */
                data = ERR_PTR(ret);

        return data;
}

/*
 * sysfs attributes
 */

static ssize_t show_fan(struct device *dev, struct device_attribute *da,
                        char *buf)
{
        int nr = to_sensor_dev_attr(da)->index;
        struct tc654_data *data = tc654_update_client(dev);
        int val;

        if (IS_ERR(data))
                return PTR_ERR(data);

        if (data->config & TC654_REG_CONFIG_RES)
                val = data->rpm_output[nr] * TC654_HIGH_RPM_RESOLUTION;
        else
                val = data->rpm_output[nr] * TC654_LOW_RPM_RESOLUTION;

        return sprintf(buf, "%d\n", val);
}

static ssize_t show_fan_min(struct device *dev, struct device_attribute *da,
                            char *buf)
{
        int nr = to_sensor_dev_attr(da)->index;
        struct tc654_data *data = tc654_update_client(dev);

        if (IS_ERR(data))
                return PTR_ERR(data);

        return sprintf(buf, "%d\n",
                       TC654_FAN_FAULT_FROM_REG(data->fan_fault[nr]));
}

static ssize_t set_fan_min(struct device *dev, struct device_attribute *da,
                           const char *buf, size_t count)
{
        int nr = to_sensor_dev_attr(da)->index;
        struct tc654_data *data = dev_get_drvdata(dev);
        struct i2c_client *client = data->client;
        unsigned long val;
        int ret;

        if (kstrtoul(buf, 10, &val))
                return -EINVAL;

        val = clamp_val(val, 0, 12750);

        mutex_lock(&data->update_lock);

        data->fan_fault[nr] = TC654_FAN_FAULT_TO_REG(val);
        ret = i2c_smbus_write_byte_data(client, TC654_REG_FAN_FAULT(nr),
                                        data->fan_fault[nr]);

        mutex_unlock(&data->update_lock);
        return ret < 0 ? ret : count;
}

static ssize_t show_fan_alarm(struct device *dev, struct device_attribute *da,
                              char *buf)
{
        int nr = to_sensor_dev_attr(da)->index;
        struct tc654_data *data = tc654_update_client(dev);
        int val;

        if (IS_ERR(data))
                return PTR_ERR(data);

        if (nr == 0)
                val = !!(data->status & TC654_REG_STATUS_F1F);
        else
                val = !!(data->status & TC654_REG_STATUS_F2F);

        return sprintf(buf, "%d\n", val);
}

static const u8 TC654_FAN_PULSE_SHIFT[] = { 1, 3 };

static ssize_t show_fan_pulses(struct device *dev, struct device_attribute *da,
                               char *buf)
{
        int nr = to_sensor_dev_attr(da)->index;
        struct tc654_data *data = tc654_update_client(dev);
        u8 val;

        if (IS_ERR(data))
                return PTR_ERR(data);

        val = BIT((data->config >> TC654_FAN_PULSE_SHIFT[nr]) & 0x03);
        return sprintf(buf, "%d\n", val);
}

static ssize_t set_fan_pulses(struct device *dev, struct device_attribute *da,
                              const char *buf, size_t count)
{
        int nr = to_sensor_dev_attr(da)->index;
        struct tc654_data *data = dev_get_drvdata(dev);
        struct i2c_client *client = data->client;
        u8 config;
        unsigned long val;
        int ret;

        if (kstrtoul(buf, 10, &val))
                return -EINVAL;

        switch (val) {
        case 1:
                config = 0;
                break;
        case 2:
                config = 1;
                break;
        case 4:
                config = 2;
                break;
        case 8:
                config = 3;
                break;
        default:
                return -EINVAL;
        }

        mutex_lock(&data->update_lock);

        data->config &= ~(0x03 << TC654_FAN_PULSE_SHIFT[nr]);
        data->config |= (config << TC654_FAN_PULSE_SHIFT[nr]);
        ret = i2c_smbus_write_byte_data(client, TC654_REG_CONFIG, data->config);

        mutex_unlock(&data->update_lock);
        return ret < 0 ? ret : count;
}

static ssize_t show_pwm_mode(struct device *dev,
                             struct device_attribute *da, char *buf)
{
        struct tc654_data *data = tc654_update_client(dev);

        if (IS_ERR(data))
                return PTR_ERR(data);

        return sprintf(buf, "%d\n", !!(data->config & TC654_REG_CONFIG_DUTYC));
}

static ssize_t set_pwm_mode(struct device *dev,
                            struct device_attribute *da,
                            const char *buf, size_t count)
{
        struct tc654_data *data = dev_get_drvdata(dev);
        struct i2c_client *client = data->client;
        unsigned long val;
        int ret;

        if (kstrtoul(buf, 10, &val))
                return -EINVAL;

        if (val != 0 && val != 1)
                return -EINVAL;

        mutex_lock(&data->update_lock);

        if (val)
                data->config |= TC654_REG_CONFIG_DUTYC;
        else
                data->config &= ~TC654_REG_CONFIG_DUTYC;

        ret = i2c_smbus_write_byte_data(client, TC654_REG_CONFIG, data->config);

        mutex_unlock(&data->update_lock);
        return ret < 0 ? ret : count;
}

static const int tc654_pwm_map[16] = { 77,  88, 102, 112, 124, 136, 148, 160,
                                      172, 184, 196, 207, 219, 231, 243, 255};

static ssize_t show_pwm(struct device *dev, struct device_attribute *da,
                        char *buf)
{
        struct tc654_data *data = tc654_update_client(dev);
        int pwm;

        if (IS_ERR(data))
                return PTR_ERR(data);

        if (data->config & TC654_REG_CONFIG_SDM)
                pwm = 0;
        else
                pwm = tc654_pwm_map[data->duty_cycle];

        return sprintf(buf, "%d\n", pwm);
}

static ssize_t set_pwm(struct device *dev, struct device_attribute *da,
                       const char *buf, size_t count)
{
        struct tc654_data *data = dev_get_drvdata(dev);
        struct i2c_client *client = data->client;
        unsigned long val;
        int ret;

        if (kstrtoul(buf, 10, &val))
                return -EINVAL;
        if (val > 255)
                return -EINVAL;

        mutex_lock(&data->update_lock);

        if (val == 0)
                data->config |= TC654_REG_CONFIG_SDM;
        else
                data->config &= ~TC654_REG_CONFIG_SDM;

        data->duty_cycle = find_closest(val, tc654_pwm_map,
                                        ARRAY_SIZE(tc654_pwm_map));

        ret = i2c_smbus_write_byte_data(client, TC654_REG_CONFIG, data->config);
        if (ret < 0)
                goto out;

        ret = i2c_smbus_write_byte_data(client, TC654_REG_DUTY_CYCLE,
                                        data->duty_cycle);

out:
        mutex_unlock(&data->update_lock);
        return ret < 0 ? ret : count;
}

static SENSOR_DEVICE_ATTR(fan1_input, S_IRUGO, show_fan, NULL, 0);
static SENSOR_DEVICE_ATTR(fan2_input, S_IRUGO, show_fan, NULL, 1);
static SENSOR_DEVICE_ATTR(fan1_min, S_IWUSR | S_IRUGO, show_fan_min,
                          set_fan_min, 0);
static SENSOR_DEVICE_ATTR(fan2_min, S_IWUSR | S_IRUGO, show_fan_min,
                          set_fan_min, 1);
static SENSOR_DEVICE_ATTR(fan1_alarm, S_IRUGO, show_fan_alarm, NULL, 0);
static SENSOR_DEVICE_ATTR(fan2_alarm, S_IRUGO, show_fan_alarm, NULL, 1);
static SENSOR_DEVICE_ATTR(fan1_pulses, S_IWUSR | S_IRUGO, show_fan_pulses,
                          set_fan_pulses, 0);
static SENSOR_DEVICE_ATTR(fan2_pulses, S_IWUSR | S_IRUGO, show_fan_pulses,
                          set_fan_pulses, 1);
static SENSOR_DEVICE_ATTR(pwm1_mode, S_IWUSR | S_IRUGO,
                          show_pwm_mode, set_pwm_mode, 0);
static SENSOR_DEVICE_ATTR(pwm1, S_IWUSR | S_IRUGO, show_pwm,
                          set_pwm, 0);

/* Driver data */
static struct attribute *tc654_attrs[] = {
        &sensor_dev_attr_fan1_input.dev_attr.attr,
        &sensor_dev_attr_fan2_input.dev_attr.attr,
        &sensor_dev_attr_fan1_min.dev_attr.attr,
        &sensor_dev_attr_fan2_min.dev_attr.attr,
        &sensor_dev_attr_fan1_alarm.dev_attr.attr,
        &sensor_dev_attr_fan2_alarm.dev_attr.attr,
        &sensor_dev_attr_fan1_pulses.dev_attr.attr,
        &sensor_dev_attr_fan2_pulses.dev_attr.attr,
        &sensor_dev_attr_pwm1_mode.dev_attr.attr,
        &sensor_dev_attr_pwm1.dev_attr.attr,
        NULL
};

ATTRIBUTE_GROUPS(tc654);

/*
 * device probe and removal
 */

static int tc654_probe(struct i2c_client *client,
                       const struct i2c_device_id *id)
{
        struct device *dev = &client->dev;
        struct tc654_data *data;
        struct device *hwmon_dev;
        int ret;

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

        data = devm_kzalloc(dev, sizeof(struct tc654_data), GFP_KERNEL);
        if (!data)
                return -ENOMEM;

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

        ret = i2c_smbus_read_byte_data(client, TC654_REG_CONFIG);
        if (ret < 0)
                return ret;

        data->config = ret;

        hwmon_dev =
            devm_hwmon_device_register_with_groups(dev, client->name, data,
                                                   tc654_groups);
        return PTR_ERR_OR_ZERO(hwmon_dev);
}

static const struct i2c_device_id tc654_id[] = {
        {"tc654", 0},
        {"tc655", 0},
        {}
};

MODULE_DEVICE_TABLE(i2c, tc654_id);

static struct i2c_driver tc654_driver = {
        .driver = {
                   .name = "tc654",
                   },
        .probe = tc654_probe,
        .id_table = tc654_id,
};

module_i2c_driver(tc654_driver);

MODULE_AUTHOR("Allied Telesis Labs");
MODULE_DESCRIPTION("Microchip TC654/TC655 driver");
MODULE_LICENSE("GPL");