/*
   * I2C multiplexer
   *
   * Copyright (c) 2008-2009 Rodolfo Giometti <giometti@linux.it>
   * Copyright (c) 2008-2009 Eurotech S.p.A. <info@eurotech.it>
   *
   * This module supports the PCA954x series of I2C multiplexer/switch chips
   * made by Philips Semiconductors.
   * This includes the:
   *	 PCA9540, PCA9542, PCA9543, PCA9544, PCA9545, PCA9546, PCA9547
   *	 and PCA9548.
   *
   * These chips are all controlled via the I2C bus itself, and all have a
   * single 8-bit register. The upstream "parent" bus fans out to two,
   * four, or eight downstream busses or channels; which of these
   * are selected is determined by the chip type and register contents. A
   * mux can select only one sub-bus at a time; a switch can select any
   * combination simultaneously.
   *
   * Based on:
   *	pca954x.c from Kumar Gala <galak@kernel.crashing.org>
   * Copyright (C) 2006
   *
   * Based on:
   *	pca954x.c from Ken Harrenstien
   * Copyright (C) 2004 Google, Inc. (Ken Harrenstien)
   *
   * Based on:
   *	i2c-virtual_cb.c from Brian Kuschak <bkuschak@yahoo.com>
   * and

   *	pca9540.c from Jean Delvare <jdelvare@suse.de>.

   *
   * This file is licensed under the terms of the GNU General Public
   * License version 2. This program is licensed "as is" without any
   * warranty of any kind, whether express or implied.
   */

  #include <linux/device.h>

  #include <linux/gpio/consumer.h>

  #include <linux/i2c.h>
  #include <linux/i2c-mux.h>

  #include <linux/i2c/pca954x.h>

  #include <linux/module.h>

  #include <linux/of.h>

  #include <linux/pm.h>

  #include <linux/slab.h>

  
  #define PCA954X_MAX_NCHANS 8
  
  enum pca_type {
  	pca_9540,
  	pca_9542,
  	pca_9543,
  	pca_9544,
  	pca_9545,
  	pca_9546,
  	pca_9547,
  	pca_9548,
  };
  
  struct pca954x {
  	enum pca_type type;
  	struct i2c_adapter *virt_adaps[PCA954X_MAX_NCHANS];
  
  	u8 last_chan;		/* last register value */
  };
  
  struct chip_desc {
  	u8 nchans;
  	u8 enable;	/* used for muxes only */
  	enum muxtype {
  		pca954x_ismux = 0,
  		pca954x_isswi
  	} muxtype;
  };
  
  /* Provide specs for the PCA954x types we know about */
  static const struct chip_desc chips[] = {
  	[pca_9540] = {
  		.nchans = 2,
  		.enable = 0x4,
  		.muxtype = pca954x_ismux,
  	},
  	[pca_9543] = {
  		.nchans = 2,
  		.muxtype = pca954x_isswi,
  	},
  	[pca_9544] = {
  		.nchans = 4,
  		.enable = 0x4,
  		.muxtype = pca954x_ismux,
  	},
  	[pca_9545] = {
  		.nchans = 4,
  		.muxtype = pca954x_isswi,
  	},
  	[pca_9547] = {
  		.nchans = 8,
  		.enable = 0x8,
  		.muxtype = pca954x_ismux,
  	},
  	[pca_9548] = {
  		.nchans = 8,
  		.muxtype = pca954x_isswi,
  	},
  };
  
  static const struct i2c_device_id pca954x_id[] = {
  	{ "pca9540", pca_9540 },
  	{ "pca9542", pca_9540 },
  	{ "pca9543", pca_9543 },
  	{ "pca9544", pca_9544 },
  	{ "pca9545", pca_9545 },
  	{ "pca9546", pca_9545 },
  	{ "pca9547", pca_9547 },
  	{ "pca9548", pca_9548 },
  	{ }
  };
  MODULE_DEVICE_TABLE(i2c, pca954x_id);
  
  /* Write to mux register. Don't use i2c_transfer()/i2c_smbus_xfer()
     for this as they will try to lock adapter a second time */
  static int pca954x_reg_write(struct i2c_adapter *adap,
  			     struct i2c_client *client, u8 val)
  {
  	int ret = -ENODEV;
  
  	if (adap->algo->master_xfer) {
  		struct i2c_msg msg;
  		char buf[1];
  
  		msg.addr = client->addr;
  		msg.flags = 0;
  		msg.len = 1;
  		buf[0] = val;
  		msg.buf = buf;

  		ret = __i2c_transfer(adap, &msg, 1);

  	} else {
  		union i2c_smbus_data data;
  		ret = adap->algo->smbus_xfer(adap, client->addr,
  					     client->flags,
  					     I2C_SMBUS_WRITE,
  					     val, I2C_SMBUS_BYTE, &data);
  	}
  
  	return ret;
  }
  
  static int pca954x_select_chan(struct i2c_adapter *adap,
  			       void *client, u32 chan)
  {
  	struct pca954x *data = i2c_get_clientdata(client);
  	const struct chip_desc *chip = &chips[data->type];
  	u8 regval;
  	int ret = 0;
  
  	/* we make switches look like muxes, not sure how to be smarter */
  	if (chip->muxtype == pca954x_ismux)
  		regval = chan | chip->enable;
  	else
  		regval = 1 << chan;
  
  	/* Only select the channel if its different from the last channel */
  	if (data->last_chan != regval) {
  		ret = pca954x_reg_write(adap, client, regval);
  		data->last_chan = regval;
  	}
  
  	return ret;
  }
  
  static int pca954x_deselect_mux(struct i2c_adapter *adap,
  				void *client, u32 chan)
  {
  	struct pca954x *data = i2c_get_clientdata(client);
  
  	/* Deselect active channel */
  	data->last_chan = 0;
  	return pca954x_reg_write(adap, client, data->last_chan);
  }
  
  /*
   * I2C init/probing/exit functions
   */

  static int pca954x_probe(struct i2c_client *client,
  			 const struct i2c_device_id *id)

  {
  	struct i2c_adapter *adap = to_i2c_adapter(client->dev.parent);

  	struct pca954x_platform_data *pdata = dev_get_platdata(&client->dev);

  	struct device_node *of_node = client->dev.of_node;
  	bool idle_disconnect_dt;

  	struct gpio_desc *gpio;

  	int num, force, class;

  	struct pca954x *data;

  	int ret;

  
  	if (!i2c_check_functionality(adap, I2C_FUNC_SMBUS_BYTE))

  		return -ENODEV;

  	data = devm_kzalloc(&client->dev, sizeof(struct pca954x), GFP_KERNEL);
  	if (!data)
  		return -ENOMEM;

  
  	i2c_set_clientdata(client, data);

  	/* Get the mux out of reset if a reset GPIO is specified. */

  	gpio = devm_gpiod_get_optional(&client->dev, "reset", GPIOD_OUT_LOW);
  	if (IS_ERR(gpio))
  		return PTR_ERR(gpio);

  	/* Write the mux register at addr to verify
  	 * that the mux is in fact present. This also
  	 * initializes the mux to disconnected state.

  	 */

  	if (i2c_smbus_write_byte(client, 0) < 0) {

  		dev_warn(&client->dev, "probe failed
  ");

  		return -ENODEV;

  	}
  
  	data->type = id->driver_data;
  	data->last_chan = 0;		   /* force the first selection */

  	idle_disconnect_dt = of_node &&
  		of_property_read_bool(of_node, "i2c-mux-idle-disconnect");

  	/* Now create an adapter for each channel */
  	for (num = 0; num < chips[data->type].nchans; num++) {

  		bool idle_disconnect_pd = false;

  		force = 0;			  /* dynamic adap number */

  		class = 0;			  /* no class by default */

  		if (pdata) {

  			if (num < pdata->num_modes) {

  				/* force static number */
  				force = pdata->modes[num].adap_id;

  				class = pdata->modes[num].class;
  			} else

  				/* discard unconfigured channels */
  				break;

  			idle_disconnect_pd = pdata->modes[num].deselect_on_exit;

  		}
  
  		data->virt_adaps[num] =

  			i2c_add_mux_adapter(adap, &client->dev, client,

  				force, num, class, pca954x_select_chan,

  				(idle_disconnect_pd || idle_disconnect_dt)

  					? pca954x_deselect_mux : NULL);
  
  		if (data->virt_adaps[num] == NULL) {
  			ret = -ENODEV;
  			dev_err(&client->dev,
  				"failed to register multiplexed adapter"
  				" %d as bus %d
  ", num, force);
  			goto virt_reg_failed;
  		}
  	}
  
  	dev_info(&client->dev,
  		 "registered %d multiplexed busses for I2C %s %s
  ",
  		 num, chips[data->type].muxtype == pca954x_ismux
  				? "mux" : "switch", client->name);
  
  	return 0;
  
  virt_reg_failed:
  	for (num--; num >= 0; num--)
  		i2c_del_mux_adapter(data->virt_adaps[num]);

  	return ret;
  }

  static int pca954x_remove(struct i2c_client *client)

  {
  	struct pca954x *data = i2c_get_clientdata(client);
  	const struct chip_desc *chip = &chips[data->type];

  	int i;

  
  	for (i = 0; i < chip->nchans; ++i)
  		if (data->virt_adaps[i]) {

  			i2c_del_mux_adapter(data->virt_adaps[i]);

  			data->virt_adaps[i] = NULL;
  		}

  	return 0;
  }

  #ifdef CONFIG_PM_SLEEP
  static int pca954x_resume(struct device *dev)
  {
  	struct i2c_client *client = to_i2c_client(dev);
  	struct pca954x *data = i2c_get_clientdata(client);
  
  	data->last_chan = 0;
  	return i2c_smbus_write_byte(client, 0);
  }
  #endif
  
  static SIMPLE_DEV_PM_OPS(pca954x_pm, NULL, pca954x_resume);

  static struct i2c_driver pca954x_driver = {
  	.driver		= {
  		.name	= "pca954x",

  		.pm	= &pca954x_pm,

  	},
  	.probe		= pca954x_probe,

  	.remove		= pca954x_remove,

  	.id_table	= pca954x_id,
  };

  module_i2c_driver(pca954x_driver);

  
  MODULE_AUTHOR("Rodolfo Giometti <giometti@linux.it>");
  MODULE_DESCRIPTION("PCA954x I2C mux/switch driver");
  MODULE_LICENSE("GPL v2");