// SPDX-License-Identifier: GPL-2.0-or-later

  /*
   * Driver for Linear Technology LTC4261 I2C Negative Voltage Hot Swap Controller
   *
   * Copyright (C) 2010 Ericsson AB.
   *
   * Derived from:
   *
   *  Driver for Linear Technology LTC4245 I2C Multiple Supply Hot Swap Controller
   *  Copyright (C) 2008 Ira W. Snyder <iws@ovro.caltech.edu>
   *
   * Datasheet: http://cds.linear.com/docs/Datasheet/42612fb.pdf

   */
  
  #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>

  
  /* chip registers */
  #define LTC4261_STATUS	0x00	/* readonly */
  #define LTC4261_FAULT	0x01
  #define LTC4261_ALERT	0x02
  #define LTC4261_CONTROL	0x03
  #define LTC4261_SENSE_H	0x04
  #define LTC4261_SENSE_L	0x05
  #define LTC4261_ADIN2_H	0x06
  #define LTC4261_ADIN2_L	0x07
  #define LTC4261_ADIN_H	0x08
  #define LTC4261_ADIN_L	0x09
  
  /*
   * Fault register bits
   */
  #define FAULT_OV	(1<<0)
  #define FAULT_UV	(1<<1)
  #define FAULT_OC	(1<<2)
  
  struct ltc4261_data {

  	struct i2c_client *client;

  
  	struct mutex update_lock;
  	bool valid;
  	unsigned long last_updated;	/* in jiffies */
  
  	/* Registers */
  	u8 regs[10];
  };
  
  static struct ltc4261_data *ltc4261_update_device(struct device *dev)
  {

  	struct ltc4261_data *data = dev_get_drvdata(dev);
  	struct i2c_client *client = data->client;

  	struct ltc4261_data *ret = data;
  
  	mutex_lock(&data->update_lock);
  
  	if (time_after(jiffies, data->last_updated + HZ / 4) || !data->valid) {
  		int i;
  
  		/* Read registers -- 0x00 to 0x09 */
  		for (i = 0; i < ARRAY_SIZE(data->regs); i++) {
  			int val;
  
  			val = i2c_smbus_read_byte_data(client, i);
  			if (unlikely(val < 0)) {
  				dev_dbg(dev,

  					"Failed to read ADC value: error %d
  ",

  					val);
  				ret = ERR_PTR(val);

  				data->valid = 0;

  				goto abort;
  			}
  			data->regs[i] = val;
  		}
  		data->last_updated = jiffies;
  		data->valid = 1;
  	}
  abort:
  	mutex_unlock(&data->update_lock);
  	return ret;
  }
  
  /* Return the voltage from the given register in mV or mA */
  static int ltc4261_get_value(struct ltc4261_data *data, u8 reg)
  {
  	u32 val;
  
  	val = (data->regs[reg] << 2) + (data->regs[reg + 1] >> 6);
  
  	switch (reg) {
  	case LTC4261_ADIN_H:
  	case LTC4261_ADIN2_H:
  		/* 2.5mV resolution. Convert to mV. */
  		val = val * 25 / 10;
  		break;
  	case LTC4261_SENSE_H:
  		/*
  		 * 62.5uV resolution. Convert to current as measured with
  		 * an 1 mOhm sense resistor, in mA. If a different sense
  		 * resistor is installed, calculate the actual current by
  		 * dividing the reported current by the sense resistor value
  		 * in mOhm.
  		 */
  		val = val * 625 / 10;
  		break;
  	default:
  		/* If we get here, the developer messed up */
  		WARN_ON_ONCE(1);
  		val = 0;
  		break;
  	}
  
  	return val;
  }

  static ssize_t ltc4261_value_show(struct device *dev,

  				  struct device_attribute *da, char *buf)
  {
  	struct sensor_device_attribute *attr = to_sensor_dev_attr(da);
  	struct ltc4261_data *data = ltc4261_update_device(dev);
  	int value;
  
  	if (IS_ERR(data))
  		return PTR_ERR(data);
  
  	value = ltc4261_get_value(data, attr->index);
  	return snprintf(buf, PAGE_SIZE, "%d
  ", value);
  }

  static ssize_t ltc4261_bool_show(struct device *dev,

  				 struct device_attribute *da, char *buf)
  {
  	struct sensor_device_attribute *attr = to_sensor_dev_attr(da);

  	struct ltc4261_data *data = ltc4261_update_device(dev);
  	u8 fault;
  
  	if (IS_ERR(data))
  		return PTR_ERR(data);
  
  	fault = data->regs[LTC4261_FAULT] & attr->index;
  	if (fault)		/* Clear reported faults in chip register */

  		i2c_smbus_write_byte_data(data->client, LTC4261_FAULT, ~fault);

  
  	return snprintf(buf, PAGE_SIZE, "%d
  ", fault ? 1 : 0);
  }
  
  /*

   * Input voltages.
   */

  static SENSOR_DEVICE_ATTR_RO(in1_input, ltc4261_value, LTC4261_ADIN_H);
  static SENSOR_DEVICE_ATTR_RO(in2_input, ltc4261_value, LTC4261_ADIN2_H);

  
  /*
   * Voltage alarms. The chip has only one set of voltage alarm status bits,
   * triggered by input voltage alarms. In many designs, those alarms are
   * associated with the ADIN2 sensor, due to the proximity of the ADIN2 pin
   * to the OV pin. ADIN2 is, however, not available on all chip variants.
   * To ensure that the alarm condition is reported to the user, report it
   * with both voltage sensors.
   */

  static SENSOR_DEVICE_ATTR_RO(in1_min_alarm, ltc4261_bool, FAULT_UV);
  static SENSOR_DEVICE_ATTR_RO(in1_max_alarm, ltc4261_bool, FAULT_OV);
  static SENSOR_DEVICE_ATTR_RO(in2_min_alarm, ltc4261_bool, FAULT_UV);
  static SENSOR_DEVICE_ATTR_RO(in2_max_alarm, ltc4261_bool, FAULT_OV);

  
  /* Currents (via sense resistor) */

  static SENSOR_DEVICE_ATTR_RO(curr1_input, ltc4261_value, LTC4261_SENSE_H);

  
  /* Overcurrent alarm */

  static SENSOR_DEVICE_ATTR_RO(curr1_max_alarm, ltc4261_bool, FAULT_OC);

  static struct attribute *ltc4261_attrs[] = {

  	&sensor_dev_attr_in1_input.dev_attr.attr,
  	&sensor_dev_attr_in1_min_alarm.dev_attr.attr,
  	&sensor_dev_attr_in1_max_alarm.dev_attr.attr,
  	&sensor_dev_attr_in2_input.dev_attr.attr,
  	&sensor_dev_attr_in2_min_alarm.dev_attr.attr,
  	&sensor_dev_attr_in2_max_alarm.dev_attr.attr,
  
  	&sensor_dev_attr_curr1_input.dev_attr.attr,
  	&sensor_dev_attr_curr1_max_alarm.dev_attr.attr,
  
  	NULL,
  };

  ATTRIBUTE_GROUPS(ltc4261);

  static int ltc4261_probe(struct i2c_client *client)

  {
  	struct i2c_adapter *adapter = client->adapter;

  	struct device *dev = &client->dev;

  	struct ltc4261_data *data;

  	struct device *hwmon_dev;

  
  	if (!i2c_check_functionality(adapter, I2C_FUNC_SMBUS_BYTE_DATA))
  		return -ENODEV;
  
  	if (i2c_smbus_read_byte_data(client, LTC4261_STATUS) < 0) {

  		dev_err(dev, "Failed to read status register
  ");

  		return -ENODEV;
  	}

  	data = devm_kzalloc(dev, sizeof(*data), GFP_KERNEL);

  	if (!data)
  		return -ENOMEM;

  	data->client = client;

  	mutex_init(&data->update_lock);
  
  	/* Clear faults */
  	i2c_smbus_write_byte_data(client, LTC4261_FAULT, 0x00);

  	hwmon_dev = devm_hwmon_device_register_with_groups(dev, client->name,
  							   data,
  							   ltc4261_groups);

  	return PTR_ERR_OR_ZERO(hwmon_dev);

  }
  
  static const struct i2c_device_id ltc4261_id[] = {
  	{"ltc4261", 0},
  	{}
  };
  
  MODULE_DEVICE_TABLE(i2c, ltc4261_id);
  
  /* This is the driver that will be inserted */
  static struct i2c_driver ltc4261_driver = {
  	.driver = {
  		   .name = "ltc4261",
  		   },

  	.probe_new = ltc4261_probe,

  	.id_table = ltc4261_id,
  };

  module_i2c_driver(ltc4261_driver);

  MODULE_AUTHOR("Guenter Roeck <linux@roeck-us.net>");

  MODULE_DESCRIPTION("LTC4261 driver");
  MODULE_LICENSE("GPL");