/*
   * Linux GPIOlib driver for the VIA VX855 integrated southbridge GPIO
   *
   * Copyright (C) 2009 VIA Technologies, Inc.
   * Copyright (C) 2010 One Laptop per Child
   * Author: Harald Welte <HaraldWelte@viatech.com>
   * All rights reserved.
   *
   * 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., 59 Temple Place, Suite 330, Boston,
   * MA 02111-1307 USA
   *
   */
  
  #include <linux/kernel.h>
  #include <linux/module.h>
  #include <linux/gpio.h>
  #include <linux/slab.h>
  #include <linux/device.h>
  #include <linux/platform_device.h>
  #include <linux/pci.h>
  #include <linux/io.h>
  
  #define MODULE_NAME "vx855_gpio"
  
  /* The VX855 south bridge has the following GPIO pins:
   *	GPI 0...13	General Purpose Input
   *	GPO 0...12	General Purpose Output
   *	GPIO 0...14	General Purpose I/O (Open-Drain)
   */
  
  #define NR_VX855_GPI	14
  #define NR_VX855_GPO	13
  #define NR_VX855_GPIO	15
  
  #define NR_VX855_GPInO	(NR_VX855_GPI + NR_VX855_GPO)
  #define NR_VX855_GP	(NR_VX855_GPI + NR_VX855_GPO + NR_VX855_GPIO)
  
  struct vx855_gpio {
  	struct gpio_chip gpio;
  	spinlock_t lock;
  	u32 io_gpi;
  	u32 io_gpo;
  	bool gpi_reserved;
  	bool gpo_reserved;
  };
  
  /* resolve a GPIx into the corresponding bit position */
  static inline u_int32_t gpi_i_bit(int i)
  {
  	if (i < 10)
  		return 1 << i;
  	else
  		return 1 << (i + 14);
  }
  
  static inline u_int32_t gpo_o_bit(int i)
  {
  	if (i < 11)
  		return 1 << i;
  	else
  		return 1 << (i + 14);
  }
  
  static inline u_int32_t gpio_i_bit(int i)
  {
  	if (i < 14)
  		return 1 << (i + 10);
  	else
  		return 1 << (i + 14);
  }
  
  static inline u_int32_t gpio_o_bit(int i)
  {
  	if (i < 14)
  		return 1 << (i + 11);
  	else
  		return 1 << (i + 13);
  }
  
  /* Mapping betwee numeric GPIO ID and the actual GPIO hardware numbering:
   * 0..13	GPI 0..13
   * 14..26	GPO 0..12
   * 27..41	GPIO 0..14
   */
  
  static int vx855gpio_direction_input(struct gpio_chip *gpio,
  				     unsigned int nr)
  {
  	struct vx855_gpio *vg = container_of(gpio, struct vx855_gpio, gpio);
  	unsigned long flags;
  	u_int32_t reg_out;
  
  	/* Real GPI bits are always in input direction */
  	if (nr < NR_VX855_GPI)
  		return 0;
  
  	/* Real GPO bits cannot be put in output direction */
  	if (nr < NR_VX855_GPInO)
  		return -EINVAL;
  
  	/* Open Drain GPIO have to be set to one */
  	spin_lock_irqsave(&vg->lock, flags);
  	reg_out = inl(vg->io_gpo);
  	reg_out |= gpio_o_bit(nr - NR_VX855_GPInO);
  	outl(reg_out, vg->io_gpo);
  	spin_unlock_irqrestore(&vg->lock, flags);
  
  	return 0;
  }
  
  static int vx855gpio_get(struct gpio_chip *gpio, unsigned int nr)
  {
  	struct vx855_gpio *vg = container_of(gpio, struct vx855_gpio, gpio);
  	u_int32_t reg_in;
  	int ret = 0;
  
  	if (nr < NR_VX855_GPI) {
  		reg_in = inl(vg->io_gpi);
  		if (reg_in & gpi_i_bit(nr))
  			ret = 1;
  	} else if (nr < NR_VX855_GPInO) {
  		/* GPO don't have an input bit, we need to read it
  		 * back from the output register */
  		reg_in = inl(vg->io_gpo);
  		if (reg_in & gpo_o_bit(nr - NR_VX855_GPI))
  			ret = 1;
  	} else {
  		reg_in = inl(vg->io_gpi);
  		if (reg_in & gpio_i_bit(nr - NR_VX855_GPInO))
  			ret = 1;
  	}
  
  	return ret;
  }
  
  static void vx855gpio_set(struct gpio_chip *gpio, unsigned int nr,
  			  int val)
  {
  	struct vx855_gpio *vg = container_of(gpio, struct vx855_gpio, gpio);
  	unsigned long flags;
  	u_int32_t reg_out;
  
  	/* True GPI cannot be switched to output mode */
  	if (nr < NR_VX855_GPI)
  		return;
  
  	spin_lock_irqsave(&vg->lock, flags);
  	reg_out = inl(vg->io_gpo);
  	if (nr < NR_VX855_GPInO) {
  		if (val)
  			reg_out |= gpo_o_bit(nr - NR_VX855_GPI);
  		else
  			reg_out &= ~gpo_o_bit(nr - NR_VX855_GPI);
  	} else {
  		if (val)
  			reg_out |= gpio_o_bit(nr - NR_VX855_GPInO);
  		else
  			reg_out &= ~gpio_o_bit(nr - NR_VX855_GPInO);
  	}
  	outl(reg_out, vg->io_gpo);
  	spin_unlock_irqrestore(&vg->lock, flags);
  }
  
  static int vx855gpio_direction_output(struct gpio_chip *gpio,
  				      unsigned int nr, int val)
  {
  	/* True GPI cannot be switched to output mode */
  	if (nr < NR_VX855_GPI)
  		return -EINVAL;
  
  	/* True GPO don't need to be switched to output mode,
  	 * and GPIO are open-drain, i.e. also need no switching,
  	 * so all we do is set the level */
  	vx855gpio_set(gpio, nr, val);
  
  	return 0;
  }
  
  static const char *vx855gpio_names[NR_VX855_GP] = {
  	"VX855_GPI0", "VX855_GPI1", "VX855_GPI2", "VX855_GPI3", "VX855_GPI4",
  	"VX855_GPI5", "VX855_GPI6", "VX855_GPI7", "VX855_GPI8", "VX855_GPI9",
  	"VX855_GPI10", "VX855_GPI11", "VX855_GPI12", "VX855_GPI13",
  	"VX855_GPO0", "VX855_GPO1", "VX855_GPO2", "VX855_GPO3", "VX855_GPO4",
  	"VX855_GPO5", "VX855_GPO6", "VX855_GPO7", "VX855_GPO8", "VX855_GPO9",
  	"VX855_GPO10", "VX855_GPO11", "VX855_GPO12",
  	"VX855_GPIO0", "VX855_GPIO1", "VX855_GPIO2", "VX855_GPIO3",
  	"VX855_GPIO4", "VX855_GPIO5", "VX855_GPIO6", "VX855_GPIO7",
  	"VX855_GPIO8", "VX855_GPIO9", "VX855_GPIO10", "VX855_GPIO11",
  	"VX855_GPIO12", "VX855_GPIO13", "VX855_GPIO14"
  };
  
  static void vx855gpio_gpio_setup(struct vx855_gpio *vg)
  {
  	struct gpio_chip *c = &vg->gpio;
  
  	c->label = "VX855 South Bridge";
  	c->owner = THIS_MODULE;
  	c->direction_input = vx855gpio_direction_input;
  	c->direction_output = vx855gpio_direction_output;
  	c->get = vx855gpio_get;
  	c->set = vx855gpio_set;
  	c->dbg_show = NULL;
  	c->base = 0;
  	c->ngpio = NR_VX855_GP;
  	c->can_sleep = false;
  	c->names = vx855gpio_names;
  }
  
  /* This platform device is ordinarily registered by the vx855 mfd driver */
  static int vx855gpio_probe(struct platform_device *pdev)
  {
  	struct resource *res_gpi;
  	struct resource *res_gpo;
  	struct vx855_gpio *vg;
  	int ret;
  
  	res_gpi = platform_get_resource(pdev, IORESOURCE_IO, 0);
  	res_gpo = platform_get_resource(pdev, IORESOURCE_IO, 1);
  	if (!res_gpi || !res_gpo)
  		return -EBUSY;
  
  	vg = kzalloc(sizeof(*vg), GFP_KERNEL);
  	if (!vg)
  		return -ENOMEM;
  
  	platform_set_drvdata(pdev, vg);
  
  	dev_info(&pdev->dev, "found VX855 GPIO controller
  ");
  	vg->io_gpi = res_gpi->start;
  	vg->io_gpo = res_gpo->start;
  	spin_lock_init(&vg->lock);
  
  	/*
  	 * A single byte is used to control various GPIO ports on the VX855,
  	 * and in the case of the OLPC XO-1.5, some of those ports are used
  	 * for switches that are interpreted and exposed through ACPI. ACPI
  	 * will have reserved the region, so our own reservation will not
  	 * succeed. Ignore and continue.
  	 */
  
  	if (!request_region(res_gpi->start, resource_size(res_gpi),
  			MODULE_NAME "_gpi"))
  		dev_warn(&pdev->dev,
  			"GPI I/O resource busy, probably claimed by ACPI
  ");
  	else
  		vg->gpi_reserved = true;
  
  	if (!request_region(res_gpo->start, resource_size(res_gpo),
  			MODULE_NAME "_gpo"))
  		dev_warn(&pdev->dev,
  			"GPO I/O resource busy, probably claimed by ACPI
  ");
  	else
  		vg->gpo_reserved = true;
  
  	vx855gpio_gpio_setup(vg);
  
  	ret = gpiochip_add(&vg->gpio);
  	if (ret) {
  		dev_err(&pdev->dev, "failed to register GPIOs
  ");
  		goto out_release;
  	}
  
  	return 0;
  
  out_release:
  	if (vg->gpi_reserved)
  		release_region(res_gpi->start, resource_size(res_gpi));
  	if (vg->gpo_reserved)
  		release_region(res_gpi->start, resource_size(res_gpo));
  	kfree(vg);
  	return ret;
  }
  
  static int vx855gpio_remove(struct platform_device *pdev)
  {
  	struct vx855_gpio *vg = platform_get_drvdata(pdev);
  	struct resource *res;
  
  	if (gpiochip_remove(&vg->gpio))
  		dev_err(&pdev->dev, "unable to remove gpio_chip?
  ");
  
  	if (vg->gpi_reserved) {
  		res = platform_get_resource(pdev, IORESOURCE_IO, 0);
  		release_region(res->start, resource_size(res));
  	}
  	if (vg->gpo_reserved) {
  		res = platform_get_resource(pdev, IORESOURCE_IO, 1);
  		release_region(res->start, resource_size(res));
  	}
  
  	kfree(vg);
  	return 0;
  }
  
  static struct platform_driver vx855gpio_driver = {
  	.driver = {
  		.name	= MODULE_NAME,
  		.owner	= THIS_MODULE,
  	},
  	.probe		= vx855gpio_probe,
  	.remove		= vx855gpio_remove,
  };
  
  module_platform_driver(vx855gpio_driver);
  
  MODULE_LICENSE("GPL");
  MODULE_AUTHOR("Harald Welte <HaraldWelte@viatech.com>");
  MODULE_DESCRIPTION("GPIO driver for the VIA VX855 chipset");
  MODULE_ALIAS("platform:vx855_gpio");