/*
   * drivers/mtd/maps/gpio-addr-flash.c
   *
   * Handle the case where a flash device is mostly addressed using physical
   * line and supplemented by GPIOs.  This way you can hook up say a 8MiB flash
   * to a 2MiB memory range and use the GPIOs to select a particular range.
   *
   * Copyright © 2000 Nicolas Pitre <nico@cam.org>
   * Copyright © 2005-2009 Analog Devices Inc.
   *
   * Enter bugs at http://blackfin.uclinux.org/
   *
   * Licensed under the GPL-2 or later.
   */
  
  #include <linux/gpio.h>
  #include <linux/init.h>
  #include <linux/io.h>
  #include <linux/kernel.h>
  #include <linux/module.h>
  #include <linux/mtd/mtd.h>
  #include <linux/mtd/map.h>
  #include <linux/mtd/partitions.h>
  #include <linux/mtd/physmap.h>
  #include <linux/platform_device.h>
  #include <linux/slab.h>
  #include <linux/types.h>
  
  #define pr_devinit(fmt, args...) \
  	({ static const char __fmt[] = fmt; printk(__fmt, ## args); })
  
  #define DRIVER_NAME "gpio-addr-flash"
  #define PFX DRIVER_NAME ": "
  
  /**
   * struct async_state - keep GPIO flash state
   *	@mtd:         MTD state for this mapping
   *	@map:         MTD map state for this flash
   *	@gpio_count:  number of GPIOs used to address
   *	@gpio_addrs:  array of GPIOs to twiddle
   *	@gpio_values: cached GPIO values
   *	@win_size:    dedicated memory size (if no GPIOs)
   */
  struct async_state {
  	struct mtd_info *mtd;
  	struct map_info map;
  	size_t gpio_count;
  	unsigned *gpio_addrs;
  	int *gpio_values;
  	unsigned long win_size;
  };
  #define gf_map_info_to_state(mi) ((struct async_state *)(mi)->map_priv_1)
  
  /**
   * gf_set_gpios() - set GPIO address lines to access specified flash offset
   *	@state: GPIO flash state
   *	@ofs:   desired offset to access
   *
   * Rather than call the GPIO framework every time, cache the last-programmed
   * value.  This speeds up sequential accesses (which are by far the most common
   * type).  We rely on the GPIO framework to treat non-zero value as high so
   * that we don't have to normalize the bits.
   */
  static void gf_set_gpios(struct async_state *state, unsigned long ofs)
  {
  	size_t i = 0;
  	int value;
  	ofs /= state->win_size;
  	do {
  		value = ofs & (1 << i);
  		if (state->gpio_values[i] != value) {
  			gpio_set_value(state->gpio_addrs[i], value);
  			state->gpio_values[i] = value;
  		}
  	} while (++i < state->gpio_count);
  }
  
  /**
   * gf_read() - read a word at the specified offset
   *	@map: MTD map state
   *	@ofs: desired offset to read
   */
  static map_word gf_read(struct map_info *map, unsigned long ofs)
  {
  	struct async_state *state = gf_map_info_to_state(map);
  	uint16_t word;
  	map_word test;
  
  	gf_set_gpios(state, ofs);
  
  	word = readw(map->virt + (ofs % state->win_size));
  	test.x[0] = word;
  	return test;
  }
  
  /**
   * gf_copy_from() - copy a chunk of data from the flash
   *	@map:  MTD map state
   *	@to:   memory to copy to
   *	@from: flash offset to copy from
   *	@len:  how much to copy
   *
   * We rely on the MTD layer to chunk up copies such that a single request here
   * will not cross a window size.  This allows us to only wiggle the GPIOs once
   * before falling back to a normal memcpy.  Reading the higher layer code shows
   * that this is indeed the case, but add a BUG_ON() to future proof.
   */
  static void gf_copy_from(struct map_info *map, void *to, unsigned long from, ssize_t len)
  {
  	struct async_state *state = gf_map_info_to_state(map);
  
  	gf_set_gpios(state, from);
  
  	/* BUG if operation crosses the win_size */
  	BUG_ON(!((from + len) % state->win_size <= (from + len)));
  
  	/* operation does not cross the win_size, so one shot it */
  	memcpy_fromio(to, map->virt + (from % state->win_size), len);
  }
  
  /**
   * gf_write() - write a word at the specified offset
   *	@map: MTD map state
   *	@ofs: desired offset to write
   */
  static void gf_write(struct map_info *map, map_word d1, unsigned long ofs)
  {
  	struct async_state *state = gf_map_info_to_state(map);
  	uint16_t d;
  
  	gf_set_gpios(state, ofs);
  
  	d = d1.x[0];
  	writew(d, map->virt + (ofs % state->win_size));
  }
  
  /**
   * gf_copy_to() - copy a chunk of data to the flash
   *	@map:  MTD map state
   *	@to:   flash offset to copy to
   *	@from: memory to copy from
   *	@len:  how much to copy
   *
   * See gf_copy_from() caveat.
   */
  static void gf_copy_to(struct map_info *map, unsigned long to,
  		       const void *from, ssize_t len)
  {
  	struct async_state *state = gf_map_info_to_state(map);
  
  	gf_set_gpios(state, to);
  
  	/* BUG if operation crosses the win_size */
  	BUG_ON(!((to + len) % state->win_size <= (to + len)));
  
  	/* operation does not cross the win_size, so one shot it */
  	memcpy_toio(map->virt + (to % state->win_size), from, len);
  }
  
  static const char * const part_probe_types[] = {
  	"cmdlinepart", "RedBoot", NULL };
  
  /**
   * gpio_flash_probe() - setup a mapping for a GPIO assisted flash
   *	@pdev: platform device
   *
   * The platform resource layout expected looks something like:
   * struct mtd_partition partitions[] = { ... };
   * struct physmap_flash_data flash_data = { ... };
   * unsigned flash_gpios[] = { GPIO_XX, GPIO_XX, ... };
   * struct resource flash_resource[] = {
   *	{
   *		.name  = "cfi_probe",
   *		.start = 0x20000000,
   *		.end   = 0x201fffff,
   *		.flags = IORESOURCE_MEM,
   *	}, {
   *		.start = (unsigned long)flash_gpios,
   *		.end   = ARRAY_SIZE(flash_gpios),
   *		.flags = IORESOURCE_IRQ,
   *	}
   * };
   * struct platform_device flash_device = {
   *	.name          = "gpio-addr-flash",
   *	.dev           = { .platform_data = &flash_data, },
   *	.num_resources = ARRAY_SIZE(flash_resource),
   *	.resource      = flash_resource,
   *	...
   * };
   */
  static int gpio_flash_probe(struct platform_device *pdev)
  {
  	size_t i, arr_size;
  	struct physmap_flash_data *pdata;
  	struct resource *memory;
  	struct resource *gpios;
  	struct async_state *state;
  
  	pdata = dev_get_platdata(&pdev->dev);
  	memory = platform_get_resource(pdev, IORESOURCE_MEM, 0);
  	gpios = platform_get_resource(pdev, IORESOURCE_IRQ, 0);
  
  	if (!memory || !gpios || !gpios->end)
  		return -EINVAL;
  
  	arr_size = sizeof(int) * gpios->end;
  	state = kzalloc(sizeof(*state) + arr_size, GFP_KERNEL);
  	if (!state)
  		return -ENOMEM;
  
  	/*
  	 * We cast start/end to known types in the boards file, so cast
  	 * away their pointer types here to the known types (gpios->xxx).
  	 */
  	state->gpio_count     = gpios->end;
  	state->gpio_addrs     = (void *)(unsigned long)gpios->start;
  	state->gpio_values    = (void *)(state + 1);
  	state->win_size       = resource_size(memory);
  	memset(state->gpio_values, 0xff, arr_size);
  
  	state->map.name       = DRIVER_NAME;
  	state->map.read       = gf_read;
  	state->map.copy_from  = gf_copy_from;
  	state->map.write      = gf_write;
  	state->map.copy_to    = gf_copy_to;
  	state->map.bankwidth  = pdata->width;
  	state->map.size       = state->win_size * (1 << state->gpio_count);
  	state->map.virt       = ioremap_nocache(memory->start, state->map.size);
  	state->map.phys       = NO_XIP;
  	state->map.map_priv_1 = (unsigned long)state;
  
  	platform_set_drvdata(pdev, state);
  
  	i = 0;
  	do {
  		if (gpio_request(state->gpio_addrs[i], DRIVER_NAME)) {
  			pr_devinit(KERN_ERR PFX "failed to request gpio %d
  ",
  				state->gpio_addrs[i]);
  			while (i--)
  				gpio_free(state->gpio_addrs[i]);
  			kfree(state);
  			return -EBUSY;
  		}
  		gpio_direction_output(state->gpio_addrs[i], 0);
  	} while (++i < state->gpio_count);
  
  	pr_devinit(KERN_NOTICE PFX "probing %d-bit flash bus
  ",
  		state->map.bankwidth * 8);
  	state->mtd = do_map_probe(memory->name, &state->map);
  	if (!state->mtd) {
  		for (i = 0; i < state->gpio_count; ++i)
  			gpio_free(state->gpio_addrs[i]);
  		kfree(state);
  		return -ENXIO;
  	}
  
  
  	mtd_device_parse_register(state->mtd, part_probe_types, NULL,
  				  pdata->parts, pdata->nr_parts);
  
  	return 0;
  }
  
  static int gpio_flash_remove(struct platform_device *pdev)
  {
  	struct async_state *state = platform_get_drvdata(pdev);
  	size_t i = 0;
  	do {
  		gpio_free(state->gpio_addrs[i]);
  	} while (++i < state->gpio_count);
  	mtd_device_unregister(state->mtd);
  	map_destroy(state->mtd);
  	kfree(state);
  	return 0;
  }
  
  static struct platform_driver gpio_flash_driver = {
  	.probe		= gpio_flash_probe,
  	.remove		= gpio_flash_remove,
  	.driver		= {
  		.name	= DRIVER_NAME,
  	},
  };
  
  module_platform_driver(gpio_flash_driver);
  
  MODULE_AUTHOR("Mike Frysinger <vapier@gentoo.org>");
  MODULE_DESCRIPTION("MTD map driver for flashes addressed physically and with gpios");
  MODULE_LICENSE("GPL");