gpio-addr-flash.c

Go to the documentation of this file.

/*
 * 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 <[email protected]>
 * 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 __devinitconst char __fmt[] = fmt; printk(__fmt, ## args); })

#define DRIVER_NAME "gpio-addr-flash"
#define PFX DRIVER_NAME ": "

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)

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);
}

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;
}

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);
}

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));
}

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 *part_probe_types[] = { "cmdlinepart", "RedBoot", NULL };

static int __devinit 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 __devexit 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     = __devexit_p(gpio_flash_remove),
    .driver     = {
        .name   = DRIVER_NAME,
    },
};

module_platform_driver(gpio_flash_driver);

MODULE_AUTHOR("Mike Frysinger <[email protected]>");
MODULE_DESCRIPTION("MTD map driver for flashes addressed physically and with gpios");
MODULE_LICENSE("GPL");