1// SPDX-License-Identifier: GPL-2.0-only
2/*======================================================================
3
4  This driver provides a method to access memory not used by the kernel
5  itself (i.e. if the kernel commandline mem=xxx is used). To actually
6  use slram at least mtdblock or mtdchar is required (for block or
7  character device access).
8
9  Usage:
10
11  if compiled as loadable module:
12    modprobe slram map=<name>,<start>,<end/offset>
13  if statically linked into the kernel use the following kernel cmd.line
14    slram=<name>,<start>,<end/offset>
15
16  <name>: name of the device that will be listed in /proc/mtd
17  <start>: start of the memory region, decimal or hex (0xabcdef)
18  <end/offset>: end of the memory region. It's possible to use +0x1234
19                to specify the offset instead of the absolute address
20
21  NOTE:
22  With slram it's only possible to map a contiguous memory region. Therefore
23  if there's a device mapped somewhere in the region specified slram will
24  fail to load (see kernel log if modprobe fails).
25
26  -
27
28  Jochen Schaeuble <psionic@psionic.de>
29
30======================================================================*/
31
32
33#include <linux/module.h>
34#include <linux/uaccess.h>
35#include <linux/types.h>
36#include <linux/kernel.h>
37#include <linux/ptrace.h>
38#include <linux/slab.h>
39#include <linux/string.h>
40#include <linux/timer.h>
41#include <linux/major.h>
42#include <linux/fs.h>
43#include <linux/ioctl.h>
44#include <linux/init.h>
45#include <linux/io.h>
46
47#include <linux/mtd/mtd.h>
48
49#define SLRAM_MAX_DEVICES_PARAMS 6		/* 3 parameters / device */
50#define SLRAM_BLK_SZ 0x4000
51
52#define T(fmt, args...) printk(KERN_DEBUG fmt, ## args)
53#define E(fmt, args...) printk(KERN_NOTICE fmt, ## args)
54
55typedef struct slram_priv {
56	u_char *start;
57	u_char *end;
58} slram_priv_t;
59
60typedef struct slram_mtd_list {
61	struct mtd_info *mtdinfo;
62	struct slram_mtd_list *next;
63} slram_mtd_list_t;
64
65#ifdef MODULE
66static char *map[SLRAM_MAX_DEVICES_PARAMS];
67
68module_param_array(map, charp, NULL, 0);
69MODULE_PARM_DESC(map, "List of memory regions to map. \"map=<name>, <start>, <length / end>\"");
70#else
71static char *map;
72#endif
73
74static slram_mtd_list_t *slram_mtdlist = NULL;
75
76static int slram_erase(struct mtd_info *, struct erase_info *);
77static int slram_point(struct mtd_info *, loff_t, size_t, size_t *, void **,
78		resource_size_t *);
79static int slram_unpoint(struct mtd_info *, loff_t, size_t);
80static int slram_read(struct mtd_info *, loff_t, size_t, size_t *, u_char *);
81static int slram_write(struct mtd_info *, loff_t, size_t, size_t *, const u_char *);
82
83static int slram_erase(struct mtd_info *mtd, struct erase_info *instr)
84{
85	slram_priv_t *priv = mtd->priv;
86
87	memset(priv->start + instr->addr, 0xff, instr->len);
88
89	return(0);
90}
91
92static int slram_point(struct mtd_info *mtd, loff_t from, size_t len,
93		size_t *retlen, void **virt, resource_size_t *phys)
94{
95	slram_priv_t *priv = mtd->priv;
96
97	*virt = priv->start + from;
98	*retlen = len;
99	return(0);
100}
101
102static int slram_unpoint(struct mtd_info *mtd, loff_t from, size_t len)
103{
104	return 0;
105}
106
107static int slram_read(struct mtd_info *mtd, loff_t from, size_t len,
108		size_t *retlen, u_char *buf)
109{
110	slram_priv_t *priv = mtd->priv;
111
112	memcpy(buf, priv->start + from, len);
113	*retlen = len;
114	return(0);
115}
116
117static int slram_write(struct mtd_info *mtd, loff_t to, size_t len,
118		size_t *retlen, const u_char *buf)
119{
120	slram_priv_t *priv = mtd->priv;
121
122	memcpy(priv->start + to, buf, len);
123	*retlen = len;
124	return(0);
125}
126
127/*====================================================================*/
128
129static int register_device(char *name, unsigned long start, unsigned long length)
130{
131	slram_mtd_list_t **curmtd;
132
133	curmtd = &slram_mtdlist;
134	while (*curmtd) {
135		curmtd = &(*curmtd)->next;
136	}
137
138	*curmtd = kmalloc(sizeof(slram_mtd_list_t), GFP_KERNEL);
139	if (!(*curmtd)) {
140		E("slram: Cannot allocate new MTD device.\n");
141		return(-ENOMEM);
142	}
143	(*curmtd)->mtdinfo = kzalloc(sizeof(struct mtd_info), GFP_KERNEL);
144	(*curmtd)->next = NULL;
145
146	if ((*curmtd)->mtdinfo)	{
147		(*curmtd)->mtdinfo->priv =
148			kzalloc(sizeof(slram_priv_t), GFP_KERNEL);
149
150		if (!(*curmtd)->mtdinfo->priv) {
151			kfree((*curmtd)->mtdinfo);
152			(*curmtd)->mtdinfo = NULL;
153		}
154	}
155
156	if (!(*curmtd)->mtdinfo) {
157		E("slram: Cannot allocate new MTD device.\n");
158		return(-ENOMEM);
159	}
160
161	if (!(((slram_priv_t *)(*curmtd)->mtdinfo->priv)->start =
162		memremap(start, length,
163			 MEMREMAP_WB | MEMREMAP_WT | MEMREMAP_WC))) {
164		E("slram: memremap failed\n");
165		return -EIO;
166	}
167	((slram_priv_t *)(*curmtd)->mtdinfo->priv)->end =
168		((slram_priv_t *)(*curmtd)->mtdinfo->priv)->start + length;
169
170
171	(*curmtd)->mtdinfo->name = name;
172	(*curmtd)->mtdinfo->size = length;
173	(*curmtd)->mtdinfo->flags = MTD_CAP_RAM;
174	(*curmtd)->mtdinfo->_erase = slram_erase;
175	(*curmtd)->mtdinfo->_point = slram_point;
176	(*curmtd)->mtdinfo->_unpoint = slram_unpoint;
177	(*curmtd)->mtdinfo->_read = slram_read;
178	(*curmtd)->mtdinfo->_write = slram_write;
179	(*curmtd)->mtdinfo->owner = THIS_MODULE;
180	(*curmtd)->mtdinfo->type = MTD_RAM;
181	(*curmtd)->mtdinfo->erasesize = SLRAM_BLK_SZ;
182	(*curmtd)->mtdinfo->writesize = 1;
183
184	if (mtd_device_register((*curmtd)->mtdinfo, NULL, 0))	{
185		E("slram: Failed to register new device\n");
186		memunmap(((slram_priv_t *)(*curmtd)->mtdinfo->priv)->start);
187		kfree((*curmtd)->mtdinfo->priv);
188		kfree((*curmtd)->mtdinfo);
189		return(-EAGAIN);
190	}
191	T("slram: Registered device %s from %luKiB to %luKiB\n", name,
192			(start / 1024), ((start + length) / 1024));
193	T("slram: Mapped from 0x%p to 0x%p\n",
194			((slram_priv_t *)(*curmtd)->mtdinfo->priv)->start,
195			((slram_priv_t *)(*curmtd)->mtdinfo->priv)->end);
196	return(0);
197}
198
199static void unregister_devices(void)
200{
201	slram_mtd_list_t *nextitem;
202
203	while (slram_mtdlist) {
204		nextitem = slram_mtdlist->next;
205		mtd_device_unregister(slram_mtdlist->mtdinfo);
206		memunmap(((slram_priv_t *)slram_mtdlist->mtdinfo->priv)->start);
207		kfree(slram_mtdlist->mtdinfo->priv);
208		kfree(slram_mtdlist->mtdinfo);
209		kfree(slram_mtdlist);
210		slram_mtdlist = nextitem;
211	}
212}
213
214static unsigned long handle_unit(unsigned long value, char *unit)
215{
216	if ((*unit == 'M') || (*unit == 'm')) {
217		return(value * 1024 * 1024);
218	} else if ((*unit == 'K') || (*unit == 'k')) {
219		return(value * 1024);
220	}
221	return(value);
222}
223
224static int parse_cmdline(char *devname, char *szstart, char *szlength)
225{
226	char *buffer;
227	unsigned long devstart;
228	unsigned long devlength;
229
230	if ((!devname) || (!szstart) || (!szlength)) {
231		unregister_devices();
232		return(-EINVAL);
233	}
234
235	devstart = simple_strtoul(szstart, &buffer, 0);
236	devstart = handle_unit(devstart, buffer);
237
238	if (*(szlength) != '+') {
239		devlength = simple_strtoul(szlength, &buffer, 0);
240		devlength = handle_unit(devlength, buffer);
241		if (devlength < devstart)
242			goto err_out;
243
244		devlength -= devstart;
245	} else {
246		devlength = simple_strtoul(szlength + 1, &buffer, 0);
247		devlength = handle_unit(devlength, buffer);
248	}
249	T("slram: devname=%s, devstart=0x%lx, devlength=0x%lx\n",
250			devname, devstart, devlength);
251	if (devlength % SLRAM_BLK_SZ != 0)
252		goto err_out;
253
254	if ((devstart = register_device(devname, devstart, devlength))){
255		unregister_devices();
256		return((int)devstart);
257	}
258	return(0);
259
260err_out:
261	E("slram: Illegal length parameter.\n");
262	return(-EINVAL);
263}
264
265#ifndef MODULE
266
267static int __init mtd_slram_setup(char *str)
268{
269	map = str;
270	return(1);
271}
272
273__setup("slram=", mtd_slram_setup);
274
275#endif
276
277static int __init init_slram(void)
278{
279	char *devname;
280
281#ifndef MODULE
282	char *devstart;
283	char *devlength;
284
285	if (!map) {
286		E("slram: not enough parameters.\n");
287		return(-EINVAL);
288	}
289	while (map) {
290		devname = devstart = devlength = NULL;
291
292		if (!(devname = strsep(&map, ","))) {
293			E("slram: No devicename specified.\n");
294			break;
295		}
296		T("slram: devname = %s\n", devname);
297		if ((!map) || (!(devstart = strsep(&map, ",")))) {
298			E("slram: No devicestart specified.\n");
299		}
300		T("slram: devstart = %s\n", devstart);
301		if ((!map) || (!(devlength = strsep(&map, ",")))) {
302			E("slram: No devicelength / -end specified.\n");
303		}
304		T("slram: devlength = %s\n", devlength);
305		if (parse_cmdline(devname, devstart, devlength) != 0) {
306			return(-EINVAL);
307		}
308	}
309#else
310	int count;
311	int i;
312
313	for (count = 0; count < SLRAM_MAX_DEVICES_PARAMS && map[count];
314			count++) {
315	}
316
317	if ((count % 3 != 0) || (count == 0)) {
318		E("slram: not enough parameters.\n");
319		return(-EINVAL);
320	}
321	for (i = 0; i < (count / 3); i++) {
322		devname = map[i * 3];
323
324		if (parse_cmdline(devname, map[i * 3 + 1], map[i * 3 + 2])!=0) {
325			return(-EINVAL);
326		}
327
328	}
329#endif /* !MODULE */
330
331	return(0);
332}
333
334static void __exit cleanup_slram(void)
335{
336	unregister_devices();
337}
338
339module_init(init_slram);
340module_exit(cleanup_slram);
341
342MODULE_LICENSE("GPL");
343MODULE_AUTHOR("Jochen Schaeuble <psionic@psionic.de>");
344MODULE_DESCRIPTION("MTD driver for uncached system RAM");
345