text: /**
   * ds2482.c - provides i2c to w1-master bridge(s)
   * Copyright (C) 2005  Ben Gardner <bgardner@wabtec.com>
   *
   * The DS2482 is a sensor chip made by Dallas Semiconductor (Maxim).
   * It is a I2C to 1-wire bridge.
   * There are two variations: -100 and -800, which have 1 or 8 1-wire ports.
   * The complete datasheet can be obtained from MAXIM's website at:
   *   http://www.maxim-ic.com/quick_view2.cfm/qv_pk/4382
   *
   * 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.
   */
  
  #include <linux/module.h>
  #include <linux/init.h>
  #include <linux/slab.h>
  #include <linux/i2c.h>
  #include <linux/delay.h>
  #include <linux/gpio.h>
  #include <linux/platform_data/ds2482.h>
  #include <asm/delay.h>
  
  #include <linux/w1.h>
  
  /**
   * Allow the active pullup to be disabled, default is enabled.
   *
   * Note from the DS2482 datasheet:
   * The APU bit controls whether an active pullup (controlled slew-rate
   * transistor) or a passive pullup (Rwpu resistor) will be used to drive
   * a 1-Wire line from low to high. When APU = 0, active pullup is disabled
   * (resistor mode). Active Pullup should always be selected unless there is
   * only a single slave on the 1-Wire line.
   */
  static int ds2482_active_pullup = 1;
  module_param_named(active_pullup, ds2482_active_pullup, int, 0644);
  MODULE_PARM_DESC(active_pullup, "Active pullup (apply to all buses): " \
  				"0-disable, 1-enable (default)");
  
  /**
   * The DS2482 registers - there are 3 registers that are addressed by a read
   * pointer. The read pointer is set by the last command executed.
   *
   * To read the data, issue a register read for any address
   */
  #define DS2482_CMD_RESET		0xF0	/* No param */
  #define DS2482_CMD_SET_READ_PTR		0xE1	/* Param: DS2482_PTR_CODE_xxx */
  #define DS2482_CMD_CHANNEL_SELECT	0xC3	/* Param: Channel byte - DS2482-800 only */
  #define DS2482_CMD_WRITE_CONFIG		0xD2	/* Param: Config byte */
  #define DS2482_CMD_1WIRE_RESET		0xB4	/* Param: None */
  #define DS2482_CMD_1WIRE_SINGLE_BIT	0x87	/* Param: Bit byte (bit7) */
  #define DS2482_CMD_1WIRE_WRITE_BYTE	0xA5	/* Param: Data byte */
  #define DS2482_CMD_1WIRE_READ_BYTE	0x96	/* Param: None */
  /* Note to read the byte, Set the ReadPtr to Data then read (any addr) */
  #define DS2482_CMD_1WIRE_TRIPLET	0x78	/* Param: Dir byte (bit7) */
  
  /* Values for DS2482_CMD_SET_READ_PTR */
  #define DS2482_PTR_CODE_STATUS		0xF0
  #define DS2482_PTR_CODE_DATA		0xE1
  #define DS2482_PTR_CODE_CHANNEL		0xD2	/* DS2482-800 only */
  #define DS2482_PTR_CODE_CONFIG		0xC3
  
  /**
   * Configure Register bit definitions
   * The top 4 bits always read 0.
   * To write, the top nibble must be the 1's compl. of the low nibble.
   */
  #define DS2482_REG_CFG_1WS		0x08	/* 1-wire speed */
  #define DS2482_REG_CFG_SPU		0x04	/* strong pull-up */
  #define DS2482_REG_CFG_PPM		0x02	/* presence pulse masking */
  #define DS2482_REG_CFG_APU		0x01	/* active pull-up */
  
  /* extra configurations - e.g. 1WS */
  int extra_config;
  
  /**
   * Write and verify codes for the CHANNEL_SELECT command (DS2482-800 only).
   * To set the channel, write the value at the index of the channel.
   * Read and compare against the corresponding value to verify the change.
   */
  static const u8 ds2482_chan_wr[8] =
  	{ 0xF0, 0xE1, 0xD2, 0xC3, 0xB4, 0xA5, 0x96, 0x87 };
  static const u8 ds2482_chan_rd[8] =
  	{ 0xB8, 0xB1, 0xAA, 0xA3, 0x9C, 0x95, 0x8E, 0x87 };
  
  
  /**
   * Status Register bit definitions (read only)
   */
  #define DS2482_REG_STS_DIR		0x80
  #define DS2482_REG_STS_TSB		0x40
  #define DS2482_REG_STS_SBR		0x20
  #define DS2482_REG_STS_RST		0x10
  #define DS2482_REG_STS_LL		0x08
  #define DS2482_REG_STS_SD		0x04
  #define DS2482_REG_STS_PPD		0x02
  #define DS2482_REG_STS_1WB		0x01
  
  /*
   * Client data (each client gets its own)
   */
  
  struct ds2482_data;
  
  struct ds2482_w1_chan {
  	struct ds2482_data	*pdev;
  	u8			channel;
  	struct w1_bus_master	w1_bm;
  };
  
  struct ds2482_data {
  	struct i2c_client	*client;
  	struct mutex		access_lock;
  	int			slpz_gpio;
  
  	/* 1-wire interface(s) */
  	int			w1_count;	/* 1 or 8 */
  	struct ds2482_w1_chan	w1_ch[8];
  
  	/* per-device values */
  	u8			channel;
  	u8			read_prt;	/* see DS2482_PTR_CODE_xxx */
  	u8			reg_config;
  };
  
  
  /**
   * Helper to calculate values for configuration register
   * @param conf the raw config value
   * @return the value w/ complements that can be written to register
   */
  static inline u8 ds2482_calculate_config(u8 conf)
  {
  	if (ds2482_active_pullup)
  		conf |= DS2482_REG_CFG_APU;
  
  	return conf | ((~conf & 0x0f) << 4);
  }
  
  
  /**
   * Sets the read pointer.
   * @param pdev		The ds2482 client pointer
   * @param read_ptr	see DS2482_PTR_CODE_xxx above
   * @return -1 on failure, 0 on success
   */
  static inline int ds2482_select_register(struct ds2482_data *pdev, u8 read_ptr)
  {
  	if (pdev->read_prt != read_ptr) {
  		if (i2c_smbus_write_byte_data(pdev->client,
  					      DS2482_CMD_SET_READ_PTR,
  					      read_ptr) < 0)
  			return -1;
  
  		pdev->read_prt = read_ptr;
  	}
  	return 0;
  }
  
  /**
   * Sends a command without a parameter
   * @param pdev	The ds2482 client pointer
   * @param cmd	DS2482_CMD_RESET,
   *		DS2482_CMD_1WIRE_RESET,
   *		DS2482_CMD_1WIRE_READ_BYTE
   * @return -1 on failure, 0 on success
   */
  static inline int ds2482_send_cmd(struct ds2482_data *pdev, u8 cmd)
  {
  	if (i2c_smbus_write_byte(pdev->client, cmd) < 0)
  		return -1;
  
  	pdev->read_prt = DS2482_PTR_CODE_STATUS;
  	return 0;
  }
  
  /**
   * Sends a command with a parameter
   * @param pdev	The ds2482 client pointer
   * @param cmd	DS2482_CMD_WRITE_CONFIG,
   *		DS2482_CMD_1WIRE_SINGLE_BIT,
   *		DS2482_CMD_1WIRE_WRITE_BYTE,
   *		DS2482_CMD_1WIRE_TRIPLET
   * @param byte	The data to send
   * @return -1 on failure, 0 on success
   */
  static inline int ds2482_send_cmd_data(struct ds2482_data *pdev,
  				       u8 cmd, u8 byte)
  {
  	if (i2c_smbus_write_byte_data(pdev->client, cmd, byte) < 0)
  		return -1;
  
  	/* all cmds leave in STATUS, except CONFIG */
  	pdev->read_prt = (cmd != DS2482_CMD_WRITE_CONFIG) ?
  			 DS2482_PTR_CODE_STATUS : DS2482_PTR_CODE_CONFIG;
  	return 0;
  }
  
  
  /*
   * 1-Wire interface code
   */
  
  #define DS2482_WAIT_IDLE_TIMEOUT	100
  
  /**
   * Waits until the 1-wire interface is idle (not busy)
   *
   * @param pdev Pointer to the device structure
   * @return the last value read from status or -1 (failure)
   */
  static int ds2482_wait_1wire_idle(struct ds2482_data *pdev)
  {
  	int temp = -1;
  	int retries = 0;
  
  	if (!ds2482_select_register(pdev, DS2482_PTR_CODE_STATUS)) {
  		do {
  			temp = i2c_smbus_read_byte(pdev->client);
  		} while ((temp >= 0) && (temp & DS2482_REG_STS_1WB) &&
  			 (++retries < DS2482_WAIT_IDLE_TIMEOUT));
  	}
  
  	if (retries >= DS2482_WAIT_IDLE_TIMEOUT)
  		pr_err("%s: timeout on channel %d\n",
  		       __func__, pdev->channel);
  
  	return temp;
  }
  
  /**
   * Selects a w1 channel.
   * The 1-wire interface must be idle before calling this function.
   *
   * @param pdev		The ds2482 client pointer
   * @param channel	0-7
   * @return		-1 (failure) or 0 (success)
   */
  static int ds2482_set_channel(struct ds2482_data *pdev, u8 channel)
  {
  	if (i2c_smbus_write_byte_data(pdev->client, DS2482_CMD_CHANNEL_SELECT,
  				      ds2482_chan_wr[channel]) < 0)
  		return -1;
  
  	pdev->read_prt = DS2482_PTR_CODE_CHANNEL;
  	pdev->channel = -1;
  	if (i2c_smbus_read_byte(pdev->client) == ds2482_chan_rd[channel]) {
  		pdev->channel = channel;
  		return 0;
  	}
  	return -1;
  }
  
  
  /**
   * Performs the touch-bit function, which writes a 0 or 1 and reads the level.
   *
   * @param data	The ds2482 channel pointer
   * @param bit	The level to write: 0 or non-zero
   * @return	The level read: 0 or 1
   */
  static u8 ds2482_w1_touch_bit(void *data, u8 bit)
  {
  	struct ds2482_w1_chan *pchan = data;
  	struct ds2482_data    *pdev = pchan->pdev;
  	int status = -1;
  
  	mutex_lock(&pdev->access_lock);
  
  	/* Select the channel */
  	ds2482_wait_1wire_idle(pdev);
  	if (pdev->w1_count > 1)
  		ds2482_set_channel(pdev, pchan->channel);
  
  	/* Send the touch command, wait until 1WB == 0, return the status */
  	if (!ds2482_send_cmd_data(pdev, DS2482_CMD_1WIRE_SINGLE_BIT,
  				  bit ? 0xFF : 0))
  		status = ds2482_wait_1wire_idle(pdev);
  
  	mutex_unlock(&pdev->access_lock);
  
  	return (status & DS2482_REG_STS_SBR) ? 1 : 0;
  }
  
  /**
   * Performs the triplet function, which reads two bits and writes a bit.
   * The bit written is determined by the two reads:
   *   00 => dbit, 01 => 0, 10 => 1
   *
   * @param data	The ds2482 channel pointer
   * @param dbit	The direction to choose if both branches are valid
   * @return	b0=read1 b1=read2 b3=bit written
   */
  static u8 ds2482_w1_triplet(void *data, u8 dbit)
  {
  	struct ds2482_w1_chan *pchan = data;
  	struct ds2482_data    *pdev = pchan->pdev;
  	int status = (3 << 5);
  
  	mutex_lock(&pdev->access_lock);
  
  	/* Select the channel */
  	ds2482_wait_1wire_idle(pdev);
  	if (pdev->w1_count > 1)
  		ds2482_set_channel(pdev, pchan->channel);
  
  	/* Send the triplet command, wait until 1WB == 0, return the status */
  	if (!ds2482_send_cmd_data(pdev, DS2482_CMD_1WIRE_TRIPLET,
  				  dbit ? 0xFF : 0))
  		status = ds2482_wait_1wire_idle(pdev);
  
  	mutex_unlock(&pdev->access_lock);
  
  	/* Decode the status */
  	return (status >> 5);
  }
  
  /**
   * Performs the write byte function.
   *
   * @param data	The ds2482 channel pointer
   * @param byte	The value to write
   */
  static void ds2482_w1_write_byte(void *data, u8 byte)
  {
  	struct ds2482_w1_chan *pchan = data;
  	struct ds2482_data    *pdev = pchan->pdev;
  
  	mutex_lock(&pdev->access_lock);
  
  	/* Select the channel */
  	ds2482_wait_1wire_idle(pdev);
  	if (pdev->w1_count > 1)
  		ds2482_set_channel(pdev, pchan->channel);
  
  	/* Send the write byte command */
  	ds2482_send_cmd_data(pdev, DS2482_CMD_1WIRE_WRITE_BYTE, byte);
  
  	mutex_unlock(&pdev->access_lock);
  }
  
  /**
   * Performs the read byte function.
   *
   * @param data	The ds2482 channel pointer
   * @return	The value read
   */
  static u8 ds2482_w1_read_byte(void *data)
  {
  	struct ds2482_w1_chan *pchan = data;
  	struct ds2482_data    *pdev = pchan->pdev;
  	int result;
  
  	mutex_lock(&pdev->access_lock);
  
  	/* Select the channel */
  	ds2482_wait_1wire_idle(pdev);
  	if (pdev->w1_count > 1)
  		ds2482_set_channel(pdev, pchan->channel);
  
  	/* Send the read byte command */
  	ds2482_send_cmd(pdev, DS2482_CMD_1WIRE_READ_BYTE);
  
  	/* Wait until 1WB == 0 */
  	ds2482_wait_1wire_idle(pdev);
  
  	/* Select the data register */
  	ds2482_select_register(pdev, DS2482_PTR_CODE_DATA);
  
  	/* Read the data byte */
  	result = i2c_smbus_read_byte(pdev->client);
  
  	mutex_unlock(&pdev->access_lock);
  
  	return result;
  }
  
  
  /**
   * Sends a reset on the 1-wire interface
   *
   * @param data	The ds2482 channel pointer
   * @return	0=Device present, 1=No device present or error
   */
  static u8 ds2482_w1_reset_bus(void *data)
  {
  	struct ds2482_w1_chan *pchan = data;
  	struct ds2482_data    *pdev = pchan->pdev;
  	int err;
  	u8 retval = 1;
  
  	mutex_lock(&pdev->access_lock);
  
  	/* Select the channel */
  	ds2482_wait_1wire_idle(pdev);
  	if (pdev->w1_count > 1)
  		ds2482_set_channel(pdev, pchan->channel);
  
  	/* Send the reset command */
  	err = ds2482_send_cmd(pdev, DS2482_CMD_1WIRE_RESET);
  	if (err >= 0) {
  		/* Wait until the reset is complete */
  		err = ds2482_wait_1wire_idle(pdev);
  		retval = !(err & DS2482_REG_STS_PPD);
  
  		/* If the chip did reset since detect, re-config it */
  		if (err & DS2482_REG_STS_RST)
  			ds2482_send_cmd_data(pdev, DS2482_CMD_WRITE_CONFIG,
  					ds2482_calculate_config(extra_config));
  	}
  
  	mutex_unlock(&pdev->access_lock);
  
  	return retval;
  }
  
  static u8 ds2482_w1_set_pullup(void *data, int delay)
  {
  	struct ds2482_w1_chan *pchan = data;
  	struct ds2482_data    *pdev = pchan->pdev;
  	u8 retval = 1;
  
  	/* if delay is non-zero activate the pullup,
  	 * the strong pullup will be automatically deactivated
  	 * by the master, so do not explicitly deactive it
  	 */
  	if (delay) {
  		/* both waits are crucial, otherwise devices might not be
  		 * powered long enough, causing e.g. a w1_therm sensor to
  		 * provide wrong conversion results
  		 */
  		ds2482_wait_1wire_idle(pdev);
  		/* note: it seems like both SPU and APU have to be set! */
  		retval = ds2482_send_cmd_data(pdev, DS2482_CMD_WRITE_CONFIG,
  			ds2482_calculate_config(extra_config|DS2482_REG_CFG_SPU|DS2482_REG_CFG_APU));
  		ds2482_wait_1wire_idle(pdev);
  	}
  
  	return retval;
  }
  
  static int ds2482_suspend(struct device *dev)
  {
  	struct i2c_client *client = to_i2c_client(dev);
  	struct ds2482_data *data = i2c_get_clientdata(client);
  
  	if (data->slpz_gpio >= 0)
  		gpio_set_value(data->slpz_gpio, 0);
  	return 0;
  }
  
  static int ds2482_resume(struct device *dev)
  {
  	struct i2c_client *client = to_i2c_client(dev);
  	struct ds2482_data *data = i2c_get_clientdata(client);
  
  	if (data->slpz_gpio >= 0)
  		gpio_set_value(data->slpz_gpio, 1);
  	return 0;
  }
  
  static int ds2482_probe(struct i2c_client *client,
  			const struct i2c_device_id *id)
  {
  	struct ds2482_data *data;
  	struct ds2482_platform_data *pdata;
  	int err = -ENODEV;
  	int temp1;
  	int idx;
  
  	if (!i2c_check_functionality(client->adapter,
  				     I2C_FUNC_SMBUS_WRITE_BYTE_DATA |
  				     I2C_FUNC_SMBUS_BYTE))
  		return -ENODEV;
  
  	if (!(data = kzalloc(sizeof(struct ds2482_data), GFP_KERNEL))) {
  		err = -ENOMEM;
  		goto exit;
  	}
  
  	data->client = client;
  	i2c_set_clientdata(client, data);
  
  	/* Reset the device (sets the read_ptr to status) */
  	if (ds2482_send_cmd(data, DS2482_CMD_RESET) < 0) {
  		dev_warn(&client->dev, "DS2482 reset failed.\n");
  		goto exit_free;
  	}
  
  	/* Sleep at least 525ns to allow the reset to complete */
  	ndelay(525);
  
  	/* Read the status byte - only reset bit and line should be set */
  	temp1 = i2c_smbus_read_byte(client);
  	if (temp1 != (DS2482_REG_STS_LL | DS2482_REG_STS_RST)) {
  		dev_warn(&client->dev, "DS2482 reset status "
  			 "0x%02X - not a DS2482\n", temp1);
  		goto exit_free;
  	}
  
  	/* Detect the 8-port version */
  	data->w1_count = 1;
  	if (ds2482_set_channel(data, 7) == 0)
  		data->w1_count = 8;
  
  	/* Set all config items to 0 (off) */
  	ds2482_send_cmd_data(data, DS2482_CMD_WRITE_CONFIG,
  		ds2482_calculate_config(extra_config));
  
  	mutex_init(&data->access_lock);
  
  	/* Register 1-wire interface(s) */
  	for (idx = 0; idx < data->w1_count; idx++) {
  		data->w1_ch[idx].pdev = data;
  		data->w1_ch[idx].channel = idx;
  
  		/* Populate all the w1 bus master stuff */
  		data->w1_ch[idx].w1_bm.data       = &data->w1_ch[idx];
  		data->w1_ch[idx].w1_bm.read_byte  = ds2482_w1_read_byte;
  		data->w1_ch[idx].w1_bm.write_byte = ds2482_w1_write_byte;
  		data->w1_ch[idx].w1_bm.touch_bit  = ds2482_w1_touch_bit;
  		data->w1_ch[idx].w1_bm.triplet    = ds2482_w1_triplet;
  		data->w1_ch[idx].w1_bm.reset_bus  = ds2482_w1_reset_bus;
  		data->w1_ch[idx].w1_bm.set_pullup = ds2482_w1_set_pullup;
  
  		err = w1_add_master_device(&data->w1_ch[idx].w1_bm);
  		if (err) {
  			data->w1_ch[idx].pdev = NULL;
  			goto exit_w1_remove;
  		}
  	}
  
  	pdata = client->dev.platform_data;
  	data->slpz_gpio = pdata ? pdata->slpz_gpio : -1;
  
  	if (data->slpz_gpio >= 0) {
  		err = gpio_request_one(data->slpz_gpio, GPIOF_OUT_INIT_HIGH,
  				       "ds2482.slpz");
  		if (err < 0)
  			goto exit_w1_remove;
  	}
  
  	return 0;
  
  exit_w1_remove:
  	for (idx = 0; idx < data->w1_count; idx++) {
  		if (data->w1_ch[idx].pdev != NULL)
  			w1_remove_master_device(&data->w1_ch[idx].w1_bm);
  	}
  exit_free:
  	kfree(data);
  exit:
  	return err;
  }
  
  static int ds2482_remove(struct i2c_client *client)
  {
  	struct ds2482_data   *data = i2c_get_clientdata(client);
  	int idx;
  
  	/* Unregister the 1-wire bridge(s) */
  	for (idx = 0; idx < data->w1_count; idx++) {
  		if (data->w1_ch[idx].pdev != NULL)
  			w1_remove_master_device(&data->w1_ch[idx].w1_bm);
  	}
  
  	if (data->slpz_gpio >= 0) {
  		gpio_set_value(data->slpz_gpio, 0);
  		gpio_free(data->slpz_gpio);
  	}
  
  	/* Free the memory */
  	kfree(data);
  	return 0;
  }
  
  /**
   * Driver data (common to all clients)
   */
  static const struct i2c_device_id ds2482_id[] = {
  	{ "ds2482", 0 },
  	{ }
  };
  MODULE_DEVICE_TABLE(i2c, ds2482_id);
  
  static const struct dev_pm_ops ds2482_pm_ops = {
  	.suspend = ds2482_suspend,
  	.resume = ds2482_resume,
  };
  
  static struct i2c_driver ds2482_driver = {
  	.driver = {
  		.name	= "ds2482",
  		.pm = &ds2482_pm_ops,
  	},
  	.probe		= ds2482_probe,
  	.remove		= ds2482_remove,
  	.id_table	= ds2482_id,
  };
  module_i2c_driver(ds2482_driver);
  
  MODULE_AUTHOR("Ben Gardner <bgardner@wabtec.com>");
  MODULE_DESCRIPTION("DS2482 driver");
  module_param(extra_config, int, S_IRUGO | S_IWUSR);
  MODULE_PARM_DESC(extra_config, "Extra Configuration settings 1=APU,2=PPM,3=SPU,8=1WS");
  
  MODULE_LICENSE("GPL");
  