drivers/mtd/chips/map_ram.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * Common code to handle map devices which are simple RAM
   4  * (C) 2000 Red Hat.
   5  */
   6
   7 #include <linux/module.h>
   8 #include <linux/types.h>
   9 #include <linux/kernel.h>
  10 #include <asm/io.h>
  11 #include <asm/byteorder.h>
  12 #include <linux/errno.h>
  13 #include <linux/slab.h>
  14 #include <linux/init.h>
  15 #include <linux/mtd/mtd.h>
  16 #include <linux/mtd/map.h>
  17
  18
  19 static int mapram_read (struct mtd_info *, loff_t, size_t, size_t *, u_char *);
  20 static int mapram_write (struct mtd_info *, loff_t, size_t, size_t *, const u_char *);
  21 static int mapram_erase (struct mtd_info *, struct erase_info *);
  22 static void mapram_nop (struct mtd_info *);
  23 static struct mtd_info *map_ram_probe(struct map_info *map);
  24 static int mapram_point (struct mtd_info *mtd, loff_t from, size_t len,
  25                          size_t *retlen, void **virt, resource_size_t *phys);
  26 static int mapram_unpoint(struct mtd_info *mtd, loff_t from, size_t len);
  27
  28
  29 static struct mtd_chip_driver mapram_chipdrv = {
  30         .probe  = map_ram_probe,
  31         .name   = "map_ram",
  32         .module = THIS_MODULE
  33 };
  34
  35 static struct mtd_info *map_ram_probe(struct map_info *map)
  36 {
  37         struct mtd_info *mtd;
  38
  39         /* Check the first byte is RAM */
  40 #if 0
  41         map_write8(map, 0x55, 0);
  42         if (map_read8(map, 0) != 0x55)
  43                 return NULL;
  44
  45         map_write8(map, 0xAA, 0);
  46         if (map_read8(map, 0) != 0xAA)
  47                 return NULL;
  48
  49         /* Check the last byte is RAM */
  50         map_write8(map, 0x55, map->size-1);
  51         if (map_read8(map, map->size-1) != 0x55)
  52                 return NULL;
  53
  54         map_write8(map, 0xAA, map->size-1);
  55         if (map_read8(map, map->size-1) != 0xAA)
  56                 return NULL;
  57 #endif
  58         /* OK. It seems to be RAM. */
  59
  60         mtd = kzalloc(sizeof(*mtd), GFP_KERNEL);
  61         if (!mtd)
  62                 return NULL;
  63
  64         map->fldrv = &mapram_chipdrv;
  65         mtd->priv = map;
  66         mtd->name = map->name;
  67         mtd->type = MTD_RAM;
  68         mtd->size = map->size;
  69         mtd->_erase = mapram_erase;
  70         mtd->_read = mapram_read;
  71         mtd->_write = mapram_write;
  72         mtd->_panic_write = mapram_write;
  73         mtd->_sync = mapram_nop;
  74         mtd->flags = MTD_CAP_RAM;
  75         mtd->writesize = 1;
  76
  77         /* Disable direct access when NO_XIP is set */
  78         if (map->phys != NO_XIP) {
  79                 mtd->_point = mapram_point;
  80                 mtd->_unpoint = mapram_unpoint;
  81         }
  82
  83         mtd->erasesize = PAGE_SIZE;
  84         while(mtd->size & (mtd->erasesize - 1))
  85                 mtd->erasesize >>= 1;
  86
  87         __module_get(THIS_MODULE);
  88         return mtd;
  89 }
  90
  91 static int mapram_point(struct mtd_info *mtd, loff_t from, size_t len,
  92                         size_t *retlen, void **virt, resource_size_t *phys)
  93 {
  94         struct map_info *map = mtd->priv;
  95
  96         if (!map->virt)
  97                 return -EINVAL;
  98         *virt = map->virt + from;
  99         if (phys)
 100                 *phys = map->phys + from;
 101         *retlen = len;
 102         return 0;
 103 }
 104
 105 static int mapram_unpoint(struct mtd_info *mtd, loff_t from, size_t len)
 106 {
 107         return 0;
 108 }
 109
 110 static int mapram_read (struct mtd_info *mtd, loff_t from, size_t len, size_t *retlen, u_char *buf)
 111 {
 112         struct map_info *map = mtd->priv;
 113
 114         map_copy_from(map, buf, from, len);
 115         *retlen = len;
 116         return 0;
 117 }
 118
 119 static int mapram_write (struct mtd_info *mtd, loff_t to, size_t len, size_t *retlen, const u_char *buf)
 120 {
 121         struct map_info *map = mtd->priv;
 122
 123         map_copy_to(map, to, buf, len);
 124         *retlen = len;
 125         return 0;
 126 }
 127
 128 static int mapram_erase (struct mtd_info *mtd, struct erase_info *instr)
 129 {
 130         /* Yeah, it's inefficient. Who cares? It's faster than a _real_
 131            flash erase. */
 132         struct map_info *map = mtd->priv;
 133         map_word allff;
 134         unsigned long i;
 135
 136         allff = map_word_ff(map);
 137         for (i=0; i<instr->len; i += map_bankwidth(map))
 138                 map_write(map, allff, instr->addr + i);
 139         return 0;
 140 }
 141
 142 static void mapram_nop(struct mtd_info *mtd)
 143 {
 144         /* Nothing to see here */
 145 }
 146
 147 static int __init map_ram_init(void)
 148 {
 149         register_mtd_chip_driver(&mapram_chipdrv);
 150         return 0;
 151 }
 152
 153 static void __exit map_ram_exit(void)
 154 {
 155         unregister_mtd_chip_driver(&mapram_chipdrv);
 156 }
 157
 158 module_init(map_ram_init);
 159 module_exit(map_ram_exit);
 160
 161 MODULE_LICENSE("GPL");
 162 MODULE_AUTHOR("David Woodhouse <dwmw2@infradead.org>");
 163 MODULE_DESCRIPTION("MTD chip driver for RAM chips");