/*
 * g760a - Driver for the Global Mixed-mode Technology Inc. G760A
 *         fan speed PWM controller chip
 *
 * Copyright (C) 2007  Herbert Valerio Riedel <hvr@gnu.org>
 *
 * Complete datasheet is available at GMT's website:
 * http://www.gmt.com.tw/product/datasheet/EDS-760A.pdf
 *
 * 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.
 */

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

enum g760a_regs {
        G760A_REG_SET_CNT = 0x00,
        G760A_REG_ACT_CNT = 0x01,
        G760A_REG_FAN_STA = 0x02
};

#define G760A_REG_FAN_STA_RPM_OFF 0x1 /* +/-20% off */
#define G760A_REG_FAN_STA_RPM_LOW 0x2 /* below 1920rpm */

/* register data is read (and cached) at most once per second */
#define G760A_UPDATE_INTERVAL (HZ)

struct g760a_data {
        struct i2c_client *client;
        struct mutex update_lock;

        /* board specific parameters */
        u32 clk; /* default 32kHz */
        u16 fan_div; /* default P=2 */

        /* g760a register cache */
        unsigned int valid:1;
        unsigned long last_updated; /* In jiffies */

        u8 set_cnt; /* PWM (period) count number; 0xff stops fan */
        u8 act_cnt; /*   formula: cnt = (CLK * 30)/(rpm * P) */
        u8 fan_sta; /* bit 0: set when actual fan speed more than 20%
                     *   outside requested fan speed
                     * bit 1: set when fan speed below 1920 rpm
                     */
};

#define G760A_DEFAULT_CLK 32768
#define G760A_DEFAULT_FAN_DIV 2

#define PWM_FROM_CNT(cnt)       (0xff-(cnt))
#define PWM_TO_CNT(pwm)         (0xff-(pwm))

static inline unsigned int rpm_from_cnt(u8 val, u32 clk, u16 div)
{
        return ((val == 0x00) ? 0 : ((clk*30)/(val*div)));
}

/* read/write wrappers */
static int g760a_read_value(struct i2c_client *client, enum g760a_regs reg)
{
        return i2c_smbus_read_byte_data(client, reg);
}

static int g760a_write_value(struct i2c_client *client, enum g760a_regs reg,
                             u16 value)
{
        return i2c_smbus_write_byte_data(client, reg, value);
}

/*
 * sysfs attributes
 */

static struct g760a_data *g760a_update_client(struct device *dev)
{
        struct g760a_data *data = dev_get_drvdata(dev);
        struct i2c_client *client = data->client;

        mutex_lock(&data->update_lock);

        if (time_after(jiffies, data->last_updated + G760A_UPDATE_INTERVAL)
            || !data->valid) {
                dev_dbg(&client->dev, "Starting g760a update\n");

                data->set_cnt = g760a_read_value(client, G760A_REG_SET_CNT);
                data->act_cnt = g760a_read_value(client, G760A_REG_ACT_CNT);
                data->fan_sta = g760a_read_value(client, G760A_REG_FAN_STA);

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

        mutex_unlock(&data->update_lock);

        return data;
}

static ssize_t show_fan(struct device *dev, struct device_attribute *da,
                        char *buf)
{
        struct g760a_data *data = g760a_update_client(dev);
        unsigned int rpm = 0;

        mutex_lock(&data->update_lock);
        if (!(data->fan_sta & G760A_REG_FAN_STA_RPM_LOW))
                rpm = rpm_from_cnt(data->act_cnt, data->clk, data->fan_div);
        mutex_unlock(&data->update_lock);

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

static ssize_t show_fan_alarm(struct device *dev, struct device_attribute *da,
                              char *buf)
{
        struct g760a_data *data = g760a_update_client(dev);

        int fan_alarm = (data->fan_sta & G760A_REG_FAN_STA_RPM_OFF) ? 1 : 0;

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

static ssize_t get_pwm(struct device *dev, struct device_attribute *da,
                       char *buf)
{
        struct g760a_data *data = g760a_update_client(dev);

        return sprintf(buf, "%d\n", PWM_FROM_CNT(data->set_cnt));
}

static ssize_t set_pwm(struct device *dev, struct device_attribute *da,
                       const char *buf, size_t count)
{
        struct g760a_data *data = g760a_update_client(dev);
        struct i2c_client *client = data->client;
        unsigned long val;

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

        mutex_lock(&data->update_lock);
        data->set_cnt = PWM_TO_CNT(clamp_val(val, 0, 255));
        g760a_write_value(client, G760A_REG_SET_CNT, data->set_cnt);
        mutex_unlock(&data->update_lock);

        return count;
}

static DEVICE_ATTR(pwm1, S_IWUSR | S_IRUGO, get_pwm, set_pwm);
static DEVICE_ATTR(fan1_input, S_IRUGO, show_fan, NULL);
static DEVICE_ATTR(fan1_alarm, S_IRUGO, show_fan_alarm, NULL);

static struct attribute *g760a_attrs[] = {
        &dev_attr_pwm1.attr,
        &dev_attr_fan1_input.attr,
        &dev_attr_fan1_alarm.attr,
        NULL
};

ATTRIBUTE_GROUPS(g760a);

/*
 * new-style driver model code
 */

static int g760a_probe(struct i2c_client *client,
                        const struct i2c_device_id *id)
{
        struct device *dev = &client->dev;
        struct g760a_data *data;
        struct device *hwmon_dev;

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

        data = devm_kzalloc(dev, sizeof(struct g760a_data), GFP_KERNEL);
        if (!data)
                return -ENOMEM;

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

        /* setup default configuration for now */
        data->fan_div = G760A_DEFAULT_FAN_DIV;
        data->clk = G760A_DEFAULT_CLK;

        hwmon_dev = devm_hwmon_device_register_with_groups(dev, client->name,
                                                           data,
                                                           g760a_groups);
        return PTR_ERR_OR_ZERO(hwmon_dev);
}

static const struct i2c_device_id g760a_id[] = {
        { "g760a", 0 },
        { }
};
MODULE_DEVICE_TABLE(i2c, g760a_id);

static struct i2c_driver g760a_driver = {
        .driver = {
                .name   = "g760a",
        },
        .probe    = g760a_probe,
        .id_table = g760a_id,
};

module_i2c_driver(g760a_driver);

MODULE_AUTHOR("Herbert Valerio Riedel <hvr@gnu.org>");
MODULE_DESCRIPTION("GMT G760A driver");
MODULE_LICENSE("GPL");