/*
 * 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 = pdev->dev.platform_data;
        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\n",
                                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\n",
                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");