/*
   *  This program is free software; you can redistribute it and/or modify it
   *  under the terms of the GNU General Public License version 2 as published
   *  by the Free Software Foundation.
   *
   *  Copyright (C) 2012 John Crispin <blogic@openwrt.org>
   */
  
  #include <linux/init.h>
  #include <linux/module.h>
  #include <linux/types.h>
  #include <linux/platform_device.h>
  #include <linux/mutex.h>
  #include <linux/gpio.h>
  #include <linux/of.h>
  #include <linux/of_gpio.h>
  #include <linux/io.h>
  #include <linux/slab.h>
  
  #include <lantiq_soc.h>
  
  /*
   * By attaching hardware latches to the EBU it is possible to create output
   * only gpios. This driver configures a special memory address, which when
   * written to outputs 16 bit to the latches.
   */
  
  #define LTQ_EBU_BUSCON	0x1e7ff		/* 16 bit access, slowest timing */
  #define LTQ_EBU_WP	0x80000000	/* write protect bit */
  
  struct ltq_mm {
  	struct of_mm_gpio_chip mmchip;
  	u16 shadow;	/* shadow the latches state */
  };
  
  /**
   * ltq_mm_apply() - write the shadow value to the ebu address.
   * @chip:     Pointer to our private data structure.
   *
   * Write the shadow value to the EBU to set the gpios. We need to set the
   * global EBU lock to make sure that PCI/MTD dont break.
   */
  static void ltq_mm_apply(struct ltq_mm *chip)
  {
  	unsigned long flags;
  
  	spin_lock_irqsave(&ebu_lock, flags);
  	ltq_ebu_w32(LTQ_EBU_BUSCON, LTQ_EBU_BUSCON1);
  	__raw_writew(chip->shadow, chip->mmchip.regs);
  	ltq_ebu_w32(LTQ_EBU_BUSCON | LTQ_EBU_WP, LTQ_EBU_BUSCON1);
  	spin_unlock_irqrestore(&ebu_lock, flags);
  }
  
  /**
   * ltq_mm_set() - gpio_chip->set - set gpios.
   * @gc:     Pointer to gpio_chip device structure.
   * @gpio:   GPIO signal number.
   * @val:    Value to be written to specified signal.
   *
   * Set the shadow value and call ltq_mm_apply.
   */
  static void ltq_mm_set(struct gpio_chip *gc, unsigned offset, int value)
  {
  	struct of_mm_gpio_chip *mm_gc = to_of_mm_gpio_chip(gc);
  	struct ltq_mm *chip =
  		container_of(mm_gc, struct ltq_mm, mmchip);
  
  	if (value)
  		chip->shadow |= (1 << offset);
  	else
  		chip->shadow &= ~(1 << offset);
  	ltq_mm_apply(chip);
  }
  
  /**
   * ltq_mm_dir_out() - gpio_chip->dir_out - set gpio direction.
   * @gc:     Pointer to gpio_chip device structure.
   * @gpio:   GPIO signal number.
   * @val:    Value to be written to specified signal.
   *
   * Same as ltq_mm_set, always returns 0.
   */
  static int ltq_mm_dir_out(struct gpio_chip *gc, unsigned offset, int value)
  {
  	ltq_mm_set(gc, offset, value);
  
  	return 0;
  }
  
  /**
   * ltq_mm_save_regs() - Set initial values of GPIO pins
   * @mm_gc: pointer to memory mapped GPIO chip structure
   */
  static void ltq_mm_save_regs(struct of_mm_gpio_chip *mm_gc)
  {
  	struct ltq_mm *chip =
  		container_of(mm_gc, struct ltq_mm, mmchip);
  
  	/* tell the ebu controller which memory address we will be using */
  	ltq_ebu_w32(CPHYSADDR(chip->mmchip.regs) | 0x1, LTQ_EBU_ADDRSEL1);
  
  	ltq_mm_apply(chip);
  }
  
  static int ltq_mm_probe(struct platform_device *pdev)
  {
  	struct resource *res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
  	struct ltq_mm *chip;
  	const __be32 *shadow;
  	int ret = 0;
  
  	if (!res) {
  		dev_err(&pdev->dev, "failed to get memory resource
  ");
  		return -ENOENT;
  	}
  
  	chip = kzalloc(sizeof(*chip), GFP_KERNEL);
  	if (!chip)
  		return -ENOMEM;
  
  	chip->mmchip.gc.ngpio = 16;
  	chip->mmchip.gc.label = "gpio-mm-ltq";
  	chip->mmchip.gc.direction_output = ltq_mm_dir_out;
  	chip->mmchip.gc.set = ltq_mm_set;
  	chip->mmchip.save_regs = ltq_mm_save_regs;
  
  	/* store the shadow value if one was passed by the devicetree */
  	shadow = of_get_property(pdev->dev.of_node, "lantiq,shadow", NULL);
  	if (shadow)
  		chip->shadow = be32_to_cpu(*shadow);
  
  	ret = of_mm_gpiochip_add(pdev->dev.of_node, &chip->mmchip);
  	if (ret)
  		kfree(chip);
  	return ret;
  }
  
  static const struct of_device_id ltq_mm_match[] = {
  	{ .compatible = "lantiq,gpio-mm" },
  	{},
  };
  MODULE_DEVICE_TABLE(of, ltq_mm_match);
  
  static struct platform_driver ltq_mm_driver = {
  	.probe = ltq_mm_probe,
  	.driver = {
  		.name = "gpio-mm-ltq",
  		.owner = THIS_MODULE,
  		.of_match_table = ltq_mm_match,
  	},
  };
  
  static int __init ltq_mm_init(void)
  {
  	return platform_driver_register(&ltq_mm_driver);
  }
  
  subsys_initcall(ltq_mm_init);