// SPDX-License-Identifier: GPL-2.0
/*
 * Common code to handle map devices which are simple RAM
 * (C) 2000 Red Hat.
 */

#include <linux/module.h>
#include <linux/types.h>
#include <linux/kernel.h>
#include <asm/io.h>
#include <asm/byteorder.h>
#include <linux/errno.h>
#include <linux/slab.h>
#include <linux/init.h>
#include <linux/mtd/mtd.h>
#include <linux/mtd/map.h>


static int mapram_read (struct mtd_info *, loff_t, size_t, size_t *, u_char *);
static int mapram_write (struct mtd_info *, loff_t, size_t, size_t *, const u_char *);
static int mapram_erase (struct mtd_info *, struct erase_info *);
static void mapram_nop (struct mtd_info *);
static struct mtd_info *map_ram_probe(struct map_info *map);
static int mapram_point (struct mtd_info *mtd, loff_t from, size_t len,
                         size_t *retlen, void **virt, resource_size_t *phys);
static int mapram_unpoint(struct mtd_info *mtd, loff_t from, size_t len);


static struct mtd_chip_driver mapram_chipdrv = {
        .probe  = map_ram_probe,
        .name   = "map_ram",
        .module = THIS_MODULE
};

static struct mtd_info *map_ram_probe(struct map_info *map)
{
        struct mtd_info *mtd;

        /* Check the first byte is RAM */
#if 0
        map_write8(map, 0x55, 0);
        if (map_read8(map, 0) != 0x55)
                return NULL;

        map_write8(map, 0xAA, 0);
        if (map_read8(map, 0) != 0xAA)
                return NULL;

        /* Check the last byte is RAM */
        map_write8(map, 0x55, map->size-1);
        if (map_read8(map, map->size-1) != 0x55)
                return NULL;

        map_write8(map, 0xAA, map->size-1);
        if (map_read8(map, map->size-1) != 0xAA)
                return NULL;
#endif
        /* OK. It seems to be RAM. */

        mtd = kzalloc_obj(*mtd);
        if (!mtd)
                return NULL;

        map->fldrv = &mapram_chipdrv;
        mtd->priv = map;
        mtd->name = map->name;
        mtd->type = MTD_RAM;
        mtd->size = map->size;
        mtd->_erase = mapram_erase;
        mtd->_read = mapram_read;
        mtd->_write = mapram_write;
        mtd->_panic_write = mapram_write;
        mtd->_sync = mapram_nop;
        mtd->flags = MTD_CAP_RAM;
        mtd->writesize = 1;

        /* Disable direct access when NO_XIP is set */
        if (map->phys != NO_XIP) {
                mtd->_point = mapram_point;
                mtd->_unpoint = mapram_unpoint;
        }

        mtd->erasesize = PAGE_SIZE;
        while(mtd->size & (mtd->erasesize - 1))
                mtd->erasesize >>= 1;

        __module_get(THIS_MODULE);
        return mtd;
}

static int mapram_point(struct mtd_info *mtd, loff_t from, size_t len,
                        size_t *retlen, void **virt, resource_size_t *phys)
{
        struct map_info *map = mtd->priv;

        if (!map->virt)
                return -EINVAL;
        *virt = map->virt + from;
        if (phys)
                *phys = map->phys + from;
        *retlen = len;
        return 0;
}

static int mapram_unpoint(struct mtd_info *mtd, loff_t from, size_t len)
{
        return 0;
}

static int mapram_read (struct mtd_info *mtd, loff_t from, size_t len, size_t *retlen, u_char *buf)
{
        struct map_info *map = mtd->priv;

        map_copy_from(map, buf, from, len);
        *retlen = len;
        return 0;
}

static int mapram_write (struct mtd_info *mtd, loff_t to, size_t len, size_t *retlen, const u_char *buf)
{
        struct map_info *map = mtd->priv;

        map_copy_to(map, to, buf, len);
        *retlen = len;
        return 0;
}

static int mapram_erase (struct mtd_info *mtd, struct erase_info *instr)
{
        /* Yeah, it's inefficient. Who cares? It's faster than a _real_
           flash erase. */
        struct map_info *map = mtd->priv;
        map_word allff;
        unsigned long i;

        allff = map_word_ff(map);
        for (i=0; i<instr->len; i += map_bankwidth(map))
                map_write(map, allff, instr->addr + i);
        return 0;
}

static void mapram_nop(struct mtd_info *mtd)
{
        /* Nothing to see here */
}

static int __init map_ram_init(void)
{
        register_mtd_chip_driver(&mapram_chipdrv);
        return 0;
}

static void __exit map_ram_exit(void)
{
        unregister_mtd_chip_driver(&mapram_chipdrv);
}

module_init(map_ram_init);
module_exit(map_ram_exit);

MODULE_LICENSE("GPL");
MODULE_AUTHOR("David Woodhouse <dwmw2@infradead.org>");
MODULE_DESCRIPTION("MTD chip driver for RAM chips");