/*
   *  htc-i2cpld.c
   *  Chip driver for an unknown CPLD chip found on omap850 HTC devices like
   *  the HTC Wizard and HTC Herald.
   *  The cpld is located on the i2c bus and acts as an input/output GPIO
   *  extender.
   *
   *  Copyright (C) 2009 Cory Maccarrone <darkstar6262@gmail.com>
   *
   *  Based on work done in the linwizard project
   *  Copyright (C) 2008-2009 Angelo Arrifano <miknix@gmail.com>
   *
   * 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.
   *
   * This program is distributed in the hope that it will be useful,
   * but WITHOUT ANY WARRANTY; without even the implied warranty of
   * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   * GNU General Public License for more details.
   *
   * You should have received a copy of the GNU General Public License
   * along with this program; if not, write to the Free Software
   * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
   */
  
  #include <linux/kernel.h>
  #include <linux/init.h>
  #include <linux/module.h>
  #include <linux/interrupt.h>
  #include <linux/platform_device.h>
  #include <linux/i2c.h>
  #include <linux/irq.h>
  #include <linux/spinlock.h>
  #include <linux/htcpld.h>
  #include <linux/gpio.h>
  #include <linux/slab.h>
  
  struct htcpld_chip {
  	spinlock_t              lock;
  
  	/* chip info */
  	u8                      reset;
  	u8                      addr;
  	struct device           *dev;
  	struct i2c_client	*client;
  
  	/* Output details */
  	u8                      cache_out;
  	struct gpio_chip        chip_out;
  
  	/* Input details */
  	u8                      cache_in;
  	struct gpio_chip        chip_in;
  
  	u16                     irqs_enabled;
  	uint                    irq_start;
  	int                     nirqs;
  
  	unsigned int		flow_type;
  	/*
  	 * Work structure to allow for setting values outside of any
  	 * possible interrupt context
  	 */
  	struct work_struct set_val_work;
  };
  
  struct htcpld_data {
  	/* irq info */
  	u16                irqs_enabled;
  	uint               irq_start;
  	int                nirqs;
  	uint               chained_irq;
  	unsigned int       int_reset_gpio_hi;
  	unsigned int       int_reset_gpio_lo;
  
  	/* htcpld info */
  	struct htcpld_chip *chip;
  	unsigned int       nchips;
  };
  
  /* There does not appear to be a way to proactively mask interrupts
   * on the htcpld chip itself.  So, we simply ignore interrupts that
   * aren't desired. */
  static void htcpld_mask(struct irq_data *data)
  {
  	struct htcpld_chip *chip = irq_data_get_irq_chip_data(data);
  	chip->irqs_enabled &= ~(1 << (data->irq - chip->irq_start));
  	pr_debug("HTCPLD mask %d %04x
  ", data->irq, chip->irqs_enabled);
  }
  static void htcpld_unmask(struct irq_data *data)
  {
  	struct htcpld_chip *chip = irq_data_get_irq_chip_data(data);
  	chip->irqs_enabled |= 1 << (data->irq - chip->irq_start);
  	pr_debug("HTCPLD unmask %d %04x
  ", data->irq, chip->irqs_enabled);
  }
  
  static int htcpld_set_type(struct irq_data *data, unsigned int flags)
  {
  	struct htcpld_chip *chip = irq_data_get_irq_chip_data(data);
  
  	if (flags & ~IRQ_TYPE_SENSE_MASK)
  		return -EINVAL;
  
  	/* We only allow edge triggering */
  	if (flags & (IRQ_TYPE_LEVEL_LOW|IRQ_TYPE_LEVEL_HIGH))
  		return -EINVAL;
  
  	chip->flow_type = flags;
  	return 0;
  }
  
  static struct irq_chip htcpld_muxed_chip = {
  	.name         = "htcpld",
  	.irq_mask     = htcpld_mask,
  	.irq_unmask   = htcpld_unmask,
  	.irq_set_type = htcpld_set_type,
  };
  
  /* To properly dispatch IRQ events, we need to read from the
   * chip.  This is an I2C action that could possibly sleep
   * (which is bad in interrupt context) -- so we use a threaded
   * interrupt handler to get around that.
   */
  static irqreturn_t htcpld_handler(int irq, void *dev)
  {
  	struct htcpld_data *htcpld = dev;
  	unsigned int i;
  	unsigned long flags;
  	int irqpin;
  
  	if (!htcpld) {
  		pr_debug("htcpld is null in ISR
  ");
  		return IRQ_HANDLED;
  	}
  
  	/*
  	 * For each chip, do a read of the chip and trigger any interrupts
  	 * desired.  The interrupts will be triggered from LSB to MSB (i.e.
  	 * bit 0 first, then bit 1, etc.)
  	 *
  	 * For chips that have no interrupt range specified, just skip 'em.
  	 */
  	for (i = 0; i < htcpld->nchips; i++) {
  		struct htcpld_chip *chip = &htcpld->chip[i];
  		struct i2c_client *client;
  		int val;
  		unsigned long uval, old_val;
  
  		if (!chip) {
  			pr_debug("chip %d is null in ISR
  ", i);
  			continue;
  		}
  
  		if (chip->nirqs == 0)
  			continue;
  
  		client = chip->client;
  		if (!client) {
  			pr_debug("client %d is null in ISR
  ", i);
  			continue;
  		}
  
  		/* Scan the chip */
  		val = i2c_smbus_read_byte_data(client, chip->cache_out);
  		if (val < 0) {
  			/* Throw a warning and skip this chip */
  			dev_warn(chip->dev, "Unable to read from chip: %d
  ",
  				 val);
  			continue;
  		}
  
  		uval = (unsigned long)val;
  
  		spin_lock_irqsave(&chip->lock, flags);
  
  		/* Save away the old value so we can compare it */
  		old_val = chip->cache_in;
  
  		/* Write the new value */
  		chip->cache_in = uval;
  
  		spin_unlock_irqrestore(&chip->lock, flags);
  
  		/*
  		 * For each bit in the data (starting at bit 0), trigger
  		 * associated interrupts.
  		 */
  		for (irqpin = 0; irqpin < chip->nirqs; irqpin++) {
  			unsigned oldb, newb, type = chip->flow_type;
  
  			irq = chip->irq_start + irqpin;
  
  			/* Run the IRQ handler, but only if the bit value
  			 * changed, and the proper flags are set */
  			oldb = (old_val >> irqpin) & 1;
  			newb = (uval >> irqpin) & 1;
  
  			if ((!oldb && newb && (type & IRQ_TYPE_EDGE_RISING)) ||
  			    (oldb && !newb && (type & IRQ_TYPE_EDGE_FALLING))) {
  				pr_debug("fire IRQ %d
  ", irqpin);
  				generic_handle_irq(irq);
  			}
  		}
  	}
  
  	/*
  	 * In order to continue receiving interrupts, the int_reset_gpio must
  	 * be asserted.
  	 */
  	if (htcpld->int_reset_gpio_hi)
  		gpio_set_value(htcpld->int_reset_gpio_hi, 1);
  	if (htcpld->int_reset_gpio_lo)
  		gpio_set_value(htcpld->int_reset_gpio_lo, 0);
  
  	return IRQ_HANDLED;
  }
  
  /*
   * The GPIO set routines can be called from interrupt context, especially if,
   * for example they're attached to the led-gpio framework and a trigger is
   * enabled.  As such, we declared work above in the htcpld_chip structure,
   * and that work is scheduled in the set routine.  The kernel can then run
   * the I2C functions, which will sleep, in process context.
   */
  static void htcpld_chip_set(struct gpio_chip *chip, unsigned offset, int val)
  {
  	struct i2c_client *client;
  	struct htcpld_chip *chip_data;
  	unsigned long flags;
  
  	chip_data = container_of(chip, struct htcpld_chip, chip_out);
  	if (!chip_data)
  		return;
  
  	client = chip_data->client;
  	if (client == NULL)
  		return;
  
  	spin_lock_irqsave(&chip_data->lock, flags);
  	if (val)
  		chip_data->cache_out |= (1 << offset);
  	else
  		chip_data->cache_out &= ~(1 << offset);
  	spin_unlock_irqrestore(&chip_data->lock, flags);
  
  	schedule_work(&(chip_data->set_val_work));
  }
  
  static void htcpld_chip_set_ni(struct work_struct *work)
  {
  	struct htcpld_chip *chip_data;
  	struct i2c_client *client;
  
  	chip_data = container_of(work, struct htcpld_chip, set_val_work);
  	client = chip_data->client;
  	i2c_smbus_read_byte_data(client, chip_data->cache_out);
  }
  
  static int htcpld_chip_get(struct gpio_chip *chip, unsigned offset)
  {
  	struct htcpld_chip *chip_data;
  	int val = 0;
  	int is_input = 0;
  
  	/* Try out first */
  	chip_data = container_of(chip, struct htcpld_chip, chip_out);
  	if (!chip_data) {
  		/* Try in */
  		is_input = 1;
  		chip_data = container_of(chip, struct htcpld_chip, chip_in);
  		if (!chip_data)
  			return -EINVAL;
  	}
  
  	/* Determine if this is an input or output GPIO */
  	if (!is_input)
  		/* Use the output cache */
  		val = (chip_data->cache_out >> offset) & 1;
  	else
  		/* Use the input cache */
  		val = (chip_data->cache_in >> offset) & 1;
  
  	if (val)
  		return 1;
  	else
  		return 0;
  }
  
  static int htcpld_direction_output(struct gpio_chip *chip,
  					unsigned offset, int value)
  {
  	htcpld_chip_set(chip, offset, value);
  	return 0;
  }
  
  static int htcpld_direction_input(struct gpio_chip *chip,
  					unsigned offset)
  {
  	/*
  	 * No-op: this function can only be called on the input chip.
  	 * We do however make sure the offset is within range.
  	 */
  	return (offset < chip->ngpio) ? 0 : -EINVAL;
  }
  
  static int htcpld_chip_to_irq(struct gpio_chip *chip, unsigned offset)
  {
  	struct htcpld_chip *chip_data;
  
  	chip_data = container_of(chip, struct htcpld_chip, chip_in);
  
  	if (offset < chip_data->nirqs)
  		return chip_data->irq_start + offset;
  	else
  		return -EINVAL;
  }
  
  static void htcpld_chip_reset(struct i2c_client *client)
  {
  	struct htcpld_chip *chip_data = i2c_get_clientdata(client);
  	if (!chip_data)
  		return;
  
  	i2c_smbus_read_byte_data(
  		client, (chip_data->cache_out = chip_data->reset));
  }
  
  static int htcpld_setup_chip_irq(
  		struct platform_device *pdev,
  		int chip_index)
  {
  	struct htcpld_data *htcpld;
  	struct device *dev = &pdev->dev;
  	struct htcpld_core_platform_data *pdata;
  	struct htcpld_chip *chip;
  	struct htcpld_chip_platform_data *plat_chip_data;
  	unsigned int irq, irq_end;
  	int ret = 0;
  
  	/* Get the platform and driver data */
  	pdata = dev_get_platdata(dev);
  	htcpld = platform_get_drvdata(pdev);
  	chip = &htcpld->chip[chip_index];
  	plat_chip_data = &pdata->chip[chip_index];
  
  	/* Setup irq handlers */
  	irq_end = chip->irq_start + chip->nirqs;
  	for (irq = chip->irq_start; irq < irq_end; irq++) {
  		irq_set_chip_and_handler(irq, &htcpld_muxed_chip,
  					 handle_simple_irq);
  		irq_set_chip_data(irq, chip);
  #ifdef CONFIG_ARM
  		set_irq_flags(irq, IRQF_VALID | IRQF_PROBE);
  #else
  		irq_set_probe(irq);
  #endif
  	}
  
  	return ret;
  }
  
  static int htcpld_register_chip_i2c(
  		struct platform_device *pdev,
  		int chip_index)
  {
  	struct htcpld_data *htcpld;
  	struct device *dev = &pdev->dev;
  	struct htcpld_core_platform_data *pdata;
  	struct htcpld_chip *chip;
  	struct htcpld_chip_platform_data *plat_chip_data;
  	struct i2c_adapter *adapter;
  	struct i2c_client *client;
  	struct i2c_board_info info;
  
  	/* Get the platform and driver data */
  	pdata = dev_get_platdata(dev);
  	htcpld = platform_get_drvdata(pdev);
  	chip = &htcpld->chip[chip_index];
  	plat_chip_data = &pdata->chip[chip_index];
  
  	adapter = i2c_get_adapter(pdata->i2c_adapter_id);
  	if (adapter == NULL) {
  		/* Eek, no such I2C adapter!  Bail out. */
  		dev_warn(dev, "Chip at i2c address 0x%x: Invalid i2c adapter %d
  ",
  			 plat_chip_data->addr, pdata->i2c_adapter_id);
  		return -ENODEV;
  	}
  
  	if (!i2c_check_functionality(adapter, I2C_FUNC_SMBUS_READ_BYTE_DATA)) {
  		dev_warn(dev, "i2c adapter %d non-functional
  ",
  			 pdata->i2c_adapter_id);
  		return -EINVAL;
  	}
  
  	memset(&info, 0, sizeof(struct i2c_board_info));
  	info.addr = plat_chip_data->addr;
  	strlcpy(info.type, "htcpld-chip", I2C_NAME_SIZE);
  	info.platform_data = chip;
  
  	/* Add the I2C device.  This calls the probe() function. */
  	client = i2c_new_device(adapter, &info);
  	if (!client) {
  		/* I2C device registration failed, contineu with the next */
  		dev_warn(dev, "Unable to add I2C device for 0x%x
  ",
  			 plat_chip_data->addr);
  		return -ENODEV;
  	}
  
  	i2c_set_clientdata(client, chip);
  	snprintf(client->name, I2C_NAME_SIZE, "Chip_0x%d", client->addr);
  	chip->client = client;
  
  	/* Reset the chip */
  	htcpld_chip_reset(client);
  	chip->cache_in = i2c_smbus_read_byte_data(client, chip->cache_out);
  
  	return 0;
  }
  
  static void htcpld_unregister_chip_i2c(
  		struct platform_device *pdev,
  		int chip_index)
  {
  	struct htcpld_data *htcpld;
  	struct htcpld_chip *chip;
  
  	/* Get the platform and driver data */
  	htcpld = platform_get_drvdata(pdev);
  	chip = &htcpld->chip[chip_index];
  
  	if (chip->client)
  		i2c_unregister_device(chip->client);
  }
  
  static int htcpld_register_chip_gpio(
  		struct platform_device *pdev,
  		int chip_index)
  {
  	struct htcpld_data *htcpld;
  	struct device *dev = &pdev->dev;
  	struct htcpld_core_platform_data *pdata;
  	struct htcpld_chip *chip;
  	struct htcpld_chip_platform_data *plat_chip_data;
  	struct gpio_chip *gpio_chip;
  	int ret = 0;
  
  	/* Get the platform and driver data */
  	pdata = dev_get_platdata(dev);
  	htcpld = platform_get_drvdata(pdev);
  	chip = &htcpld->chip[chip_index];
  	plat_chip_data = &pdata->chip[chip_index];
  
  	/* Setup the GPIO chips */
  	gpio_chip = &(chip->chip_out);
  	gpio_chip->label           = "htcpld-out";
  	gpio_chip->dev             = dev;
  	gpio_chip->owner           = THIS_MODULE;
  	gpio_chip->get             = htcpld_chip_get;
  	gpio_chip->set             = htcpld_chip_set;
  	gpio_chip->direction_input = NULL;
  	gpio_chip->direction_output = htcpld_direction_output;
  	gpio_chip->base            = plat_chip_data->gpio_out_base;
  	gpio_chip->ngpio           = plat_chip_data->num_gpios;
  
  	gpio_chip = &(chip->chip_in);
  	gpio_chip->label           = "htcpld-in";
  	gpio_chip->dev             = dev;
  	gpio_chip->owner           = THIS_MODULE;
  	gpio_chip->get             = htcpld_chip_get;
  	gpio_chip->set             = NULL;
  	gpio_chip->direction_input = htcpld_direction_input;
  	gpio_chip->direction_output = NULL;
  	gpio_chip->to_irq          = htcpld_chip_to_irq;
  	gpio_chip->base            = plat_chip_data->gpio_in_base;
  	gpio_chip->ngpio           = plat_chip_data->num_gpios;
  
  	/* Add the GPIO chips */
  	ret = gpiochip_add(&(chip->chip_out));
  	if (ret) {
  		dev_warn(dev, "Unable to register output GPIOs for 0x%x: %d
  ",
  			 plat_chip_data->addr, ret);
  		return ret;
  	}
  
  	ret = gpiochip_add(&(chip->chip_in));
  	if (ret) {
  		int error;
  
  		dev_warn(dev, "Unable to register input GPIOs for 0x%x: %d
  ",
  			 plat_chip_data->addr, ret);
  
  		error = gpiochip_remove(&(chip->chip_out));
  		if (error)
  			dev_warn(dev, "Error while trying to unregister gpio chip: %d
  ", error);
  
  		return ret;
  	}
  
  	return 0;
  }
  
  static int htcpld_setup_chips(struct platform_device *pdev)
  {
  	struct htcpld_data *htcpld;
  	struct device *dev = &pdev->dev;
  	struct htcpld_core_platform_data *pdata;
  	int i;
  
  	/* Get the platform and driver data */
  	pdata = dev_get_platdata(dev);
  	htcpld = platform_get_drvdata(pdev);
  
  	/* Setup each chip's output GPIOs */
  	htcpld->nchips = pdata->num_chip;
  	htcpld->chip = devm_kzalloc(dev, sizeof(struct htcpld_chip) * htcpld->nchips,
  				    GFP_KERNEL);
  	if (!htcpld->chip) {
  		dev_warn(dev, "Unable to allocate memory for chips
  ");
  		return -ENOMEM;
  	}
  
  	/* Add the chips as best we can */
  	for (i = 0; i < htcpld->nchips; i++) {
  		int ret;
  
  		/* Setup the HTCPLD chips */
  		htcpld->chip[i].reset = pdata->chip[i].reset;
  		htcpld->chip[i].cache_out = pdata->chip[i].reset;
  		htcpld->chip[i].cache_in = 0;
  		htcpld->chip[i].dev = dev;
  		htcpld->chip[i].irq_start = pdata->chip[i].irq_base;
  		htcpld->chip[i].nirqs = pdata->chip[i].num_irqs;
  
  		INIT_WORK(&(htcpld->chip[i].set_val_work), &htcpld_chip_set_ni);
  		spin_lock_init(&(htcpld->chip[i].lock));
  
  		/* Setup the interrupts for the chip */
  		if (htcpld->chained_irq) {
  			ret = htcpld_setup_chip_irq(pdev, i);
  			if (ret)
  				continue;
  		}
  
  		/* Register the chip with I2C */
  		ret = htcpld_register_chip_i2c(pdev, i);
  		if (ret)
  			continue;
  
  
  		/* Register the chips with the GPIO subsystem */
  		ret = htcpld_register_chip_gpio(pdev, i);
  		if (ret) {
  			/* Unregister the chip from i2c and continue */
  			htcpld_unregister_chip_i2c(pdev, i);
  			continue;
  		}
  
  		dev_info(dev, "Registered chip at 0x%x
  ", pdata->chip[i].addr);
  	}
  
  	return 0;
  }
  
  static int htcpld_core_probe(struct platform_device *pdev)
  {
  	struct htcpld_data *htcpld;
  	struct device *dev = &pdev->dev;
  	struct htcpld_core_platform_data *pdata;
  	struct resource *res;
  	int ret = 0;
  
  	if (!dev)
  		return -ENODEV;
  
  	pdata = dev_get_platdata(dev);
  	if (!pdata) {
  		dev_warn(dev, "Platform data not found for htcpld core!
  ");
  		return -ENXIO;
  	}
  
  	htcpld = devm_kzalloc(dev, sizeof(struct htcpld_data), GFP_KERNEL);
  	if (!htcpld)
  		return -ENOMEM;
  
  	/* Find chained irq */
  	res = platform_get_resource(pdev, IORESOURCE_IRQ, 0);
  	if (res) {
  		int flags;
  		htcpld->chained_irq = res->start;
  
  		/* Setup the chained interrupt handler */
  		flags = IRQF_TRIGGER_FALLING | IRQF_TRIGGER_RISING;
  		ret = request_threaded_irq(htcpld->chained_irq,
  					   NULL, htcpld_handler,
  					   flags, pdev->name, htcpld);
  		if (ret) {
  			dev_warn(dev, "Unable to setup chained irq handler: %d
  ", ret);
  			return ret;
  		} else
  			device_init_wakeup(dev, 0);
  	}
  
  	/* Set the driver data */
  	platform_set_drvdata(pdev, htcpld);
  
  	/* Setup the htcpld chips */
  	ret = htcpld_setup_chips(pdev);
  	if (ret)
  		return ret;
  
  	/* Request the GPIO(s) for the int reset and set them up */
  	if (pdata->int_reset_gpio_hi) {
  		ret = gpio_request(pdata->int_reset_gpio_hi, "htcpld-core");
  		if (ret) {
  			/*
  			 * If it failed, that sucks, but we can probably
  			 * continue on without it.
  			 */
  			dev_warn(dev, "Unable to request int_reset_gpio_hi -- interrupts may not work
  ");
  			htcpld->int_reset_gpio_hi = 0;
  		} else {
  			htcpld->int_reset_gpio_hi = pdata->int_reset_gpio_hi;
  			gpio_set_value(htcpld->int_reset_gpio_hi, 1);
  		}
  	}
  
  	if (pdata->int_reset_gpio_lo) {
  		ret = gpio_request(pdata->int_reset_gpio_lo, "htcpld-core");
  		if (ret) {
  			/*
  			 * If it failed, that sucks, but we can probably
  			 * continue on without it.
  			 */
  			dev_warn(dev, "Unable to request int_reset_gpio_lo -- interrupts may not work
  ");
  			htcpld->int_reset_gpio_lo = 0;
  		} else {
  			htcpld->int_reset_gpio_lo = pdata->int_reset_gpio_lo;
  			gpio_set_value(htcpld->int_reset_gpio_lo, 0);
  		}
  	}
  
  	dev_info(dev, "Initialized successfully
  ");
  	return 0;
  }
  
  /* The I2C Driver -- used internally */
  static const struct i2c_device_id htcpld_chip_id[] = {
  	{ "htcpld-chip", 0 },
  	{ }
  };
  MODULE_DEVICE_TABLE(i2c, htcpld_chip_id);
  
  
  static struct i2c_driver htcpld_chip_driver = {
  	.driver = {
  		.name	= "htcpld-chip",
  	},
  	.id_table = htcpld_chip_id,
  };
  
  /* The Core Driver */
  static struct platform_driver htcpld_core_driver = {
  	.driver = {
  		.name = "i2c-htcpld",
  	},
  };
  
  static int __init htcpld_core_init(void)
  {
  	int ret;
  
  	/* Register the I2C Chip driver */
  	ret = i2c_add_driver(&htcpld_chip_driver);
  	if (ret)
  		return ret;
  
  	/* Probe for our chips */
  	return platform_driver_probe(&htcpld_core_driver, htcpld_core_probe);
  }
  
  static void __exit htcpld_core_exit(void)
  {
  	i2c_del_driver(&htcpld_chip_driver);
  	platform_driver_unregister(&htcpld_core_driver);
  }
  
  module_init(htcpld_core_init);
  module_exit(htcpld_core_exit);
  
  MODULE_AUTHOR("Cory Maccarrone <darkstar6262@gmail.com>");
  MODULE_DESCRIPTION("I2C HTC PLD Driver");
  MODULE_LICENSE("GPL");