/*
   * 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>
  
  static const struct i2c_device_id g760a_id[] = {
  	{ "g760a", 0 },
  	{ }
  };
  MODULE_DEVICE_TABLE(i2c, g760a_id);
  
  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 device *hwmon_dev;
  	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)));
  }
  
  /* new-style driver model */
  static int g760a_probe(struct i2c_client *client,
  			const struct i2c_device_id *id);
  static int g760a_remove(struct i2c_client *client);
  
  static struct i2c_driver g760a_driver = {
  	.driver = {
  		.name	= "g760a",
  	},
  	.probe	  = g760a_probe,
  	.remove	  = g760a_remove,
  	.id_table = g760a_id,
  };
  
  /* 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 i2c_client *client = to_i2c_client(dev);
  	struct g760a_data *data = i2c_get_clientdata(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
  ");
  
  		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
  ", 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
  ", 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
  ", 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 i2c_client *client = to_i2c_client(dev);
  	struct g760a_data *data = g760a_update_client(dev);
  	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_attributes[] = {
  	&dev_attr_pwm1.attr,
  	&dev_attr_fan1_input.attr,
  	&dev_attr_fan1_alarm.attr,
  	NULL
  };
  
  static const struct attribute_group g760a_group = {
  	.attrs = g760a_attributes,
  };
  
  /*
   * new-style driver model code
   */
  
  static int g760a_probe(struct i2c_client *client,
  			const struct i2c_device_id *id)
  {
  	struct g760a_data *data;
  	int err;
  
  	if (!i2c_check_functionality(client->adapter,
  				     I2C_FUNC_SMBUS_BYTE_DATA))
  		return -EIO;
  
  	data = devm_kzalloc(&client->dev, sizeof(struct g760a_data),
  			    GFP_KERNEL);
  	if (!data)
  		return -ENOMEM;
  
  	i2c_set_clientdata(client, data);
  
  	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;
  
  	/* Register sysfs hooks */
  	err = sysfs_create_group(&client->dev.kobj, &g760a_group);
  	if (err)
  		return err;
  
  	data->hwmon_dev = hwmon_device_register(&client->dev);
  	if (IS_ERR(data->hwmon_dev)) {
  		err = PTR_ERR(data->hwmon_dev);
  		goto error_hwmon_device_register;
  	}
  
  	return 0;
  
  error_hwmon_device_register:
  	sysfs_remove_group(&client->dev.kobj, &g760a_group);
  	return err;
  }
  
  static int g760a_remove(struct i2c_client *client)
  {
  	struct g760a_data *data = i2c_get_clientdata(client);
  	hwmon_device_unregister(data->hwmon_dev);
  	sysfs_remove_group(&client->dev.kobj, &g760a_group);
  	return 0;
  }
  
  module_i2c_driver(g760a_driver);
  
  MODULE_AUTHOR("Herbert Valerio Riedel <hvr@gnu.org>");
  MODULE_DESCRIPTION("GMT G760A driver");
  MODULE_LICENSE("GPL");