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
19static int mapram_read (struct mtd_info *, loff_t, size_t, size_t *, u_char *);
20static int mapram_write (struct mtd_info *, loff_t, size_t, size_t *, const u_char *);
21static int mapram_erase (struct mtd_info *, struct erase_info *);
22static void mapram_nop (struct mtd_info *);
23static struct mtd_info *map_ram_probe(struct map_info *map);
24static int mapram_point (struct mtd_info *mtd, loff_t from, size_t len,
25			 size_t *retlen, void **virt, resource_size_t *phys);
26static int mapram_unpoint(struct mtd_info *mtd, loff_t from, size_t len);
27
28
29static struct mtd_chip_driver mapram_chipdrv = {
30	.probe	= map_ram_probe,
31	.name	= "map_ram",
32	.module	= THIS_MODULE
33};
34
35static 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->_point = mapram_point;
74	mtd->_sync = mapram_nop;
75	mtd->_unpoint = mapram_unpoint;
76	mtd->flags = MTD_CAP_RAM;
77	mtd->writesize = 1;
78
79	mtd->erasesize = PAGE_SIZE;
80 	while(mtd->size & (mtd->erasesize - 1))
81		mtd->erasesize >>= 1;
82
83	__module_get(THIS_MODULE);
84	return mtd;
85}
86
87static int mapram_point(struct mtd_info *mtd, loff_t from, size_t len,
88			size_t *retlen, void **virt, resource_size_t *phys)
89{
90	struct map_info *map = mtd->priv;
91
92	if (!map->virt)
93		return -EINVAL;
94	*virt = map->virt + from;
95	if (phys)
96		*phys = map->phys + from;
97	*retlen = len;
98	return 0;
99}
100
101static int mapram_unpoint(struct mtd_info *mtd, loff_t from, size_t len)
102{
103	return 0;
104}
105
106static int mapram_read (struct mtd_info *mtd, loff_t from, size_t len, size_t *retlen, u_char *buf)
107{
108	struct map_info *map = mtd->priv;
109
110	map_copy_from(map, buf, from, len);
111	*retlen = len;
112	return 0;
113}
114
115static int mapram_write (struct mtd_info *mtd, loff_t to, size_t len, size_t *retlen, const u_char *buf)
116{
117	struct map_info *map = mtd->priv;
118
119	map_copy_to(map, to, buf, len);
120	*retlen = len;
121	return 0;
122}
123
124static int mapram_erase (struct mtd_info *mtd, struct erase_info *instr)
125{
126	/* Yeah, it's inefficient. Who cares? It's faster than a _real_
127	   flash erase. */
128	struct map_info *map = mtd->priv;
129	map_word allff;
130	unsigned long i;
131
132	allff = map_word_ff(map);
133	for (i=0; i<instr->len; i += map_bankwidth(map))
134		map_write(map, allff, instr->addr + i);
135	return 0;
136}
137
138static void mapram_nop(struct mtd_info *mtd)
139{
140	/* Nothing to see here */
141}
142
143static int __init map_ram_init(void)
144{
145	register_mtd_chip_driver(&mapram_chipdrv);
146	return 0;
147}
148
149static void __exit map_ram_exit(void)
150{
151	unregister_mtd_chip_driver(&mapram_chipdrv);
152}
153
154module_init(map_ram_init);
155module_exit(map_ram_exit);
156
157MODULE_LICENSE("GPL");
158MODULE_AUTHOR("David Woodhouse <dwmw2@infradead.org>");
159MODULE_DESCRIPTION("MTD chip driver for RAM chips");
160