/*
   * 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>
  #include <linux/jiffies.h>
  #include <linux/i2c/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;
  
  	const struct attribute_group *groups[3];
  
  	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)) {
  		dev_dbg(&client->dev, "Marking GPIOs invalid
  ");
  		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) {
  
  		dev_dbg(&client->dev, "Starting ltc4245 update
  ");
  
  		/* 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 = 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_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;
  }
  
  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
  ", 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
  ", 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
  ", 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
  ", (reg & mask) ? 1 : 0);
  }
  
  static ssize_t ltc4245_show_gpio(struct device *dev,
  				 struct device_attribute *da,
  				 char *buf)
  {
  	struct sensor_device_attribute *attr = to_sensor_dev_attr(da);
  	struct ltc4245_data *data = ltc4245_update_device(dev);
  	int val = data->gpios[attr->index];
  
  	/* handle stale GPIO's */
  	if (val < 0)
  		return val;
  
  	/* Convert to millivolts and print */
  	return snprintf(buf, PAGE_SIZE, "%u
  ", val * 10);
  }
  
  /* Construct a sensor_device_attribute structure for each register */
  
  /* Input voltages */
  static SENSOR_DEVICE_ATTR(in1_input, S_IRUGO, ltc4245_show_voltage, NULL,
  			  LTC4245_12VIN);
  static SENSOR_DEVICE_ATTR(in2_input, S_IRUGO, ltc4245_show_voltage, NULL,
  			  LTC4245_5VIN);
  static SENSOR_DEVICE_ATTR(in3_input, S_IRUGO, ltc4245_show_voltage, NULL,
  			  LTC4245_3VIN);
  static SENSOR_DEVICE_ATTR(in4_input, S_IRUGO, ltc4245_show_voltage, NULL,
  			  LTC4245_VEEIN);
  
  /* Input undervoltage alarms */
  static SENSOR_DEVICE_ATTR_2(in1_min_alarm, S_IRUGO, ltc4245_show_alarm, NULL,
  			    1 << 0, LTC4245_FAULT1);
  static SENSOR_DEVICE_ATTR_2(in2_min_alarm, S_IRUGO, ltc4245_show_alarm, NULL,
  			    1 << 1, LTC4245_FAULT1);
  static SENSOR_DEVICE_ATTR_2(in3_min_alarm, S_IRUGO, ltc4245_show_alarm, NULL,
  			    1 << 2, LTC4245_FAULT1);
  static SENSOR_DEVICE_ATTR_2(in4_min_alarm, S_IRUGO, ltc4245_show_alarm, NULL,
  			    1 << 3, LTC4245_FAULT1);
  
  /* Currents (via sense resistor) */
  static SENSOR_DEVICE_ATTR(curr1_input, S_IRUGO, ltc4245_show_current, NULL,
  			  LTC4245_12VSENSE);
  static SENSOR_DEVICE_ATTR(curr2_input, S_IRUGO, ltc4245_show_current, NULL,
  			  LTC4245_5VSENSE);
  static SENSOR_DEVICE_ATTR(curr3_input, S_IRUGO, ltc4245_show_current, NULL,
  			  LTC4245_3VSENSE);
  static SENSOR_DEVICE_ATTR(curr4_input, S_IRUGO, ltc4245_show_current, NULL,
  			  LTC4245_VEESENSE);
  
  /* Overcurrent alarms */
  static SENSOR_DEVICE_ATTR_2(curr1_max_alarm, S_IRUGO, ltc4245_show_alarm, NULL,
  			    1 << 4, LTC4245_FAULT1);
  static SENSOR_DEVICE_ATTR_2(curr2_max_alarm, S_IRUGO, ltc4245_show_alarm, NULL,
  			    1 << 5, LTC4245_FAULT1);
  static SENSOR_DEVICE_ATTR_2(curr3_max_alarm, S_IRUGO, ltc4245_show_alarm, NULL,
  			    1 << 6, LTC4245_FAULT1);
  static SENSOR_DEVICE_ATTR_2(curr4_max_alarm, S_IRUGO, ltc4245_show_alarm, NULL,
  			    1 << 7, LTC4245_FAULT1);
  
  /* Output voltages */
  static SENSOR_DEVICE_ATTR(in5_input, S_IRUGO, ltc4245_show_voltage, NULL,
  			  LTC4245_12VOUT);
  static SENSOR_DEVICE_ATTR(in6_input, S_IRUGO, ltc4245_show_voltage, NULL,
  			  LTC4245_5VOUT);
  static SENSOR_DEVICE_ATTR(in7_input, S_IRUGO, ltc4245_show_voltage, NULL,
  			  LTC4245_3VOUT);
  static SENSOR_DEVICE_ATTR(in8_input, S_IRUGO, ltc4245_show_voltage, NULL,
  			  LTC4245_VEEOUT);
  
  /* Power Bad alarms */
  static SENSOR_DEVICE_ATTR_2(in5_min_alarm, S_IRUGO, ltc4245_show_alarm, NULL,
  			    1 << 0, LTC4245_FAULT2);
  static SENSOR_DEVICE_ATTR_2(in6_min_alarm, S_IRUGO, ltc4245_show_alarm, NULL,
  			    1 << 1, LTC4245_FAULT2);
  static SENSOR_DEVICE_ATTR_2(in7_min_alarm, S_IRUGO, ltc4245_show_alarm, NULL,
  			    1 << 2, LTC4245_FAULT2);
  static SENSOR_DEVICE_ATTR_2(in8_min_alarm, S_IRUGO, ltc4245_show_alarm, NULL,
  			    1 << 3, LTC4245_FAULT2);
  
  /* GPIO voltages */
  static SENSOR_DEVICE_ATTR(in9_input, S_IRUGO, ltc4245_show_gpio, NULL, 0);
  static SENSOR_DEVICE_ATTR(in10_input, S_IRUGO, ltc4245_show_gpio, NULL, 1);
  static SENSOR_DEVICE_ATTR(in11_input, S_IRUGO, ltc4245_show_gpio, NULL, 2);
  
  /* Power Consumption (virtual) */
  static SENSOR_DEVICE_ATTR(power1_input, S_IRUGO, ltc4245_show_power, NULL,
  			  LTC4245_12VSENSE);
  static SENSOR_DEVICE_ATTR(power2_input, S_IRUGO, ltc4245_show_power, NULL,
  			  LTC4245_5VSENSE);
  static SENSOR_DEVICE_ATTR(power3_input, S_IRUGO, ltc4245_show_power, NULL,
  			  LTC4245_3VSENSE);
  static SENSOR_DEVICE_ATTR(power4_input, S_IRUGO, ltc4245_show_power, NULL,
  			  LTC4245_VEESENSE);
  
  /*
   * Finally, construct an array of pointers to members of the above objects,
   * as required for sysfs_create_group()
   */
  static struct attribute *ltc4245_std_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_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 struct attribute *ltc4245_gpio_attributes[] = {
  	&sensor_dev_attr_in10_input.dev_attr.attr,
  	&sensor_dev_attr_in11_input.dev_attr.attr,
  	NULL,
  };
  
  static const struct attribute_group ltc4245_std_group = {
  	.attrs = ltc4245_std_attributes,
  };
  
  static const struct attribute_group ltc4245_gpio_group = {
  	.attrs = ltc4245_gpio_attributes,
  };
  
  static void ltc4245_sysfs_add_groups(struct ltc4245_data *data)
  {
  	/* standard sysfs attributes */
  	data->groups[0] = &ltc4245_std_group;
  
  	/* if we're using the extra gpio support, register it's attributes */
  	if (data->use_extra_gpios)
  		data->groups[1] = &ltc4245_gpio_group;
  }
  
  static bool ltc4245_use_extra_gpios(struct i2c_client *client)
  {
  	struct ltc4245_platform_data *pdata = dev_get_platdata(&client->dev);
  #ifdef CONFIG_OF
  	struct device_node *np = client->dev.of_node;
  #endif
  
  	/* prefer platform data */
  	if (pdata)
  		return pdata->use_extra_gpios;
  
  #ifdef CONFIG_OF
  	/* fallback on OF */
  	if (of_find_property(np, "ltc4245,use-extra-gpios", NULL))
  		return true;
  #endif
  
  	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);
  
  	/* Add sysfs hooks */
  	ltc4245_sysfs_add_groups(data);
  
  	hwmon_dev = hwmon_device_register_with_groups(&client->dev,
  						      client->name, data,
  						      data->groups);
  	if (IS_ERR(hwmon_dev))
  		return PTR_ERR(hwmon_dev);
  
  	i2c_set_clientdata(client, hwmon_dev);
  
  	return 0;
  }
  
  static int ltc4245_remove(struct i2c_client *client)
  {
  	struct device *hwmon_dev = i2c_get_clientdata(client);
  
  	hwmon_device_unregister(hwmon_dev);
  
  	return 0;
  }
  
  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,
  	.remove		= ltc4245_remove,
  	.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");