xref: /openbmc/linux/drivers/mtd/devices/slram.c (revision 31b90347)
1 /*======================================================================
2 
3   This driver provides a method to access memory not used by the kernel
4   itself (i.e. if the kernel commandline mem=xxx is used). To actually
5   use slram at least mtdblock or mtdchar is required (for block or
6   character device access).
7 
8   Usage:
9 
10   if compiled as loadable module:
11     modprobe slram map=<name>,<start>,<end/offset>
12   if statically linked into the kernel use the following kernel cmd.line
13     slram=<name>,<start>,<end/offset>
14 
15   <name>: name of the device that will be listed in /proc/mtd
16   <start>: start of the memory region, decimal or hex (0xabcdef)
17   <end/offset>: end of the memory region. It's possible to use +0x1234
18                 to specify the offset instead of the absolute address
19 
20   NOTE:
21   With slram it's only possible to map a contiguous memory region. Therefore
22   if there's a device mapped somewhere in the region specified slram will
23   fail to load (see kernel log if modprobe fails).
24 
25   -
26 
27   Jochen Schaeuble <psionic@psionic.de>
28 
29 ======================================================================*/
30 
31 
32 #include <linux/module.h>
33 #include <asm/uaccess.h>
34 #include <linux/types.h>
35 #include <linux/kernel.h>
36 #include <linux/ptrace.h>
37 #include <linux/slab.h>
38 #include <linux/string.h>
39 #include <linux/timer.h>
40 #include <linux/major.h>
41 #include <linux/fs.h>
42 #include <linux/ioctl.h>
43 #include <linux/init.h>
44 #include <asm/io.h>
45 
46 #include <linux/mtd/mtd.h>
47 
48 #define SLRAM_MAX_DEVICES_PARAMS 6		/* 3 parameters / device */
49 #define SLRAM_BLK_SZ 0x4000
50 
51 #define T(fmt, args...) printk(KERN_DEBUG fmt, ## args)
52 #define E(fmt, args...) printk(KERN_NOTICE fmt, ## args)
53 
54 typedef struct slram_priv {
55 	u_char *start;
56 	u_char *end;
57 } slram_priv_t;
58 
59 typedef struct slram_mtd_list {
60 	struct mtd_info *mtdinfo;
61 	struct slram_mtd_list *next;
62 } slram_mtd_list_t;
63 
64 #ifdef MODULE
65 static char *map[SLRAM_MAX_DEVICES_PARAMS];
66 
67 module_param_array(map, charp, NULL, 0);
68 MODULE_PARM_DESC(map, "List of memory regions to map. \"map=<name>, <start>, <length / end>\"");
69 #else
70 static char *map;
71 #endif
72 
73 static slram_mtd_list_t *slram_mtdlist = NULL;
74 
75 static int slram_erase(struct mtd_info *, struct erase_info *);
76 static int slram_point(struct mtd_info *, loff_t, size_t, size_t *, void **,
77 		resource_size_t *);
78 static int slram_unpoint(struct mtd_info *, loff_t, size_t);
79 static int slram_read(struct mtd_info *, loff_t, size_t, size_t *, u_char *);
80 static int slram_write(struct mtd_info *, loff_t, size_t, size_t *, const u_char *);
81 
82 static int slram_erase(struct mtd_info *mtd, struct erase_info *instr)
83 {
84 	slram_priv_t *priv = mtd->priv;
85 
86 	memset(priv->start + instr->addr, 0xff, instr->len);
87 	/* This'll catch a few races. Free the thing before returning :)
88 	 * I don't feel at all ashamed. This kind of thing is possible anyway
89 	 * with flash, but unlikely.
90 	 */
91 	instr->state = MTD_ERASE_DONE;
92 	mtd_erase_callback(instr);
93 	return(0);
94 }
95 
96 static int slram_point(struct mtd_info *mtd, loff_t from, size_t len,
97 		size_t *retlen, void **virt, resource_size_t *phys)
98 {
99 	slram_priv_t *priv = mtd->priv;
100 
101 	*virt = priv->start + from;
102 	*retlen = len;
103 	return(0);
104 }
105 
106 static int slram_unpoint(struct mtd_info *mtd, loff_t from, size_t len)
107 {
108 	return 0;
109 }
110 
111 static int slram_read(struct mtd_info *mtd, loff_t from, size_t len,
112 		size_t *retlen, u_char *buf)
113 {
114 	slram_priv_t *priv = mtd->priv;
115 
116 	memcpy(buf, priv->start + from, len);
117 	*retlen = len;
118 	return(0);
119 }
120 
121 static int slram_write(struct mtd_info *mtd, loff_t to, size_t len,
122 		size_t *retlen, const u_char *buf)
123 {
124 	slram_priv_t *priv = mtd->priv;
125 
126 	memcpy(priv->start + to, buf, len);
127 	*retlen = len;
128 	return(0);
129 }
130 
131 /*====================================================================*/
132 
133 static int register_device(char *name, unsigned long start, unsigned long length)
134 {
135 	slram_mtd_list_t **curmtd;
136 
137 	curmtd = &slram_mtdlist;
138 	while (*curmtd) {
139 		curmtd = &(*curmtd)->next;
140 	}
141 
142 	*curmtd = kmalloc(sizeof(slram_mtd_list_t), GFP_KERNEL);
143 	if (!(*curmtd)) {
144 		E("slram: Cannot allocate new MTD device.\n");
145 		return(-ENOMEM);
146 	}
147 	(*curmtd)->mtdinfo = kzalloc(sizeof(struct mtd_info), GFP_KERNEL);
148 	(*curmtd)->next = NULL;
149 
150 	if ((*curmtd)->mtdinfo)	{
151 		(*curmtd)->mtdinfo->priv =
152 			kzalloc(sizeof(slram_priv_t), GFP_KERNEL);
153 
154 		if (!(*curmtd)->mtdinfo->priv) {
155 			kfree((*curmtd)->mtdinfo);
156 			(*curmtd)->mtdinfo = NULL;
157 		}
158 	}
159 
160 	if (!(*curmtd)->mtdinfo) {
161 		E("slram: Cannot allocate new MTD device.\n");
162 		return(-ENOMEM);
163 	}
164 
165 	if (!(((slram_priv_t *)(*curmtd)->mtdinfo->priv)->start =
166 				ioremap(start, length))) {
167 		E("slram: ioremap failed\n");
168 		return -EIO;
169 	}
170 	((slram_priv_t *)(*curmtd)->mtdinfo->priv)->end =
171 		((slram_priv_t *)(*curmtd)->mtdinfo->priv)->start + length;
172 
173 
174 	(*curmtd)->mtdinfo->name = name;
175 	(*curmtd)->mtdinfo->size = length;
176 	(*curmtd)->mtdinfo->flags = MTD_CAP_RAM;
177 	(*curmtd)->mtdinfo->_erase = slram_erase;
178 	(*curmtd)->mtdinfo->_point = slram_point;
179 	(*curmtd)->mtdinfo->_unpoint = slram_unpoint;
180 	(*curmtd)->mtdinfo->_read = slram_read;
181 	(*curmtd)->mtdinfo->_write = slram_write;
182 	(*curmtd)->mtdinfo->owner = THIS_MODULE;
183 	(*curmtd)->mtdinfo->type = MTD_RAM;
184 	(*curmtd)->mtdinfo->erasesize = SLRAM_BLK_SZ;
185 	(*curmtd)->mtdinfo->writesize = 1;
186 
187 	if (mtd_device_register((*curmtd)->mtdinfo, NULL, 0))	{
188 		E("slram: Failed to register new device\n");
189 		iounmap(((slram_priv_t *)(*curmtd)->mtdinfo->priv)->start);
190 		kfree((*curmtd)->mtdinfo->priv);
191 		kfree((*curmtd)->mtdinfo);
192 		return(-EAGAIN);
193 	}
194 	T("slram: Registered device %s from %luKiB to %luKiB\n", name,
195 			(start / 1024), ((start + length) / 1024));
196 	T("slram: Mapped from 0x%p to 0x%p\n",
197 			((slram_priv_t *)(*curmtd)->mtdinfo->priv)->start,
198 			((slram_priv_t *)(*curmtd)->mtdinfo->priv)->end);
199 	return(0);
200 }
201 
202 static void unregister_devices(void)
203 {
204 	slram_mtd_list_t *nextitem;
205 
206 	while (slram_mtdlist) {
207 		nextitem = slram_mtdlist->next;
208 		mtd_device_unregister(slram_mtdlist->mtdinfo);
209 		iounmap(((slram_priv_t *)slram_mtdlist->mtdinfo->priv)->start);
210 		kfree(slram_mtdlist->mtdinfo->priv);
211 		kfree(slram_mtdlist->mtdinfo);
212 		kfree(slram_mtdlist);
213 		slram_mtdlist = nextitem;
214 	}
215 }
216 
217 static unsigned long handle_unit(unsigned long value, char *unit)
218 {
219 	if ((*unit == 'M') || (*unit == 'm')) {
220 		return(value * 1024 * 1024);
221 	} else if ((*unit == 'K') || (*unit == 'k')) {
222 		return(value * 1024);
223 	}
224 	return(value);
225 }
226 
227 static int parse_cmdline(char *devname, char *szstart, char *szlength)
228 {
229 	char *buffer;
230 	unsigned long devstart;
231 	unsigned long devlength;
232 
233 	if ((!devname) || (!szstart) || (!szlength)) {
234 		unregister_devices();
235 		return(-EINVAL);
236 	}
237 
238 	devstart = simple_strtoul(szstart, &buffer, 0);
239 	devstart = handle_unit(devstart, buffer);
240 
241 	if (*(szlength) != '+') {
242 		devlength = simple_strtoul(szlength, &buffer, 0);
243 		devlength = handle_unit(devlength, buffer);
244 		if (devlength < devstart)
245 			goto err_out;
246 
247 		devlength -= devstart;
248 	} else {
249 		devlength = simple_strtoul(szlength + 1, &buffer, 0);
250 		devlength = handle_unit(devlength, buffer);
251 	}
252 	T("slram: devname=%s, devstart=0x%lx, devlength=0x%lx\n",
253 			devname, devstart, devlength);
254 	if (devlength % SLRAM_BLK_SZ != 0)
255 		goto err_out;
256 
257 	if ((devstart = register_device(devname, devstart, devlength))){
258 		unregister_devices();
259 		return((int)devstart);
260 	}
261 	return(0);
262 
263 err_out:
264 	E("slram: Illegal length parameter.\n");
265 	return(-EINVAL);
266 }
267 
268 #ifndef MODULE
269 
270 static int __init mtd_slram_setup(char *str)
271 {
272 	map = str;
273 	return(1);
274 }
275 
276 __setup("slram=", mtd_slram_setup);
277 
278 #endif
279 
280 static int __init init_slram(void)
281 {
282 	char *devname;
283 	int i;
284 
285 #ifndef MODULE
286 	char *devstart;
287 	char *devlength;
288 
289 	i = 0;
290 
291 	if (!map) {
292 		E("slram: not enough parameters.\n");
293 		return(-EINVAL);
294 	}
295 	while (map) {
296 		devname = devstart = devlength = NULL;
297 
298 		if (!(devname = strsep(&map, ","))) {
299 			E("slram: No devicename specified.\n");
300 			break;
301 		}
302 		T("slram: devname = %s\n", devname);
303 		if ((!map) || (!(devstart = strsep(&map, ",")))) {
304 			E("slram: No devicestart specified.\n");
305 		}
306 		T("slram: devstart = %s\n", devstart);
307 		if ((!map) || (!(devlength = strsep(&map, ",")))) {
308 			E("slram: No devicelength / -end specified.\n");
309 		}
310 		T("slram: devlength = %s\n", devlength);
311 		if (parse_cmdline(devname, devstart, devlength) != 0) {
312 			return(-EINVAL);
313 		}
314 	}
315 #else
316 	int count;
317 
318 	for (count = 0; count < SLRAM_MAX_DEVICES_PARAMS && map[count];
319 			count++) {
320 	}
321 
322 	if ((count % 3 != 0) || (count == 0)) {
323 		E("slram: not enough parameters.\n");
324 		return(-EINVAL);
325 	}
326 	for (i = 0; i < (count / 3); i++) {
327 		devname = map[i * 3];
328 
329 		if (parse_cmdline(devname, map[i * 3 + 1], map[i * 3 + 2])!=0) {
330 			return(-EINVAL);
331 		}
332 
333 	}
334 #endif /* !MODULE */
335 
336 	return(0);
337 }
338 
339 static void __exit cleanup_slram(void)
340 {
341 	unregister_devices();
342 }
343 
344 module_init(init_slram);
345 module_exit(cleanup_slram);
346 
347 MODULE_LICENSE("GPL");
348 MODULE_AUTHOR("Jochen Schaeuble <psionic@psionic.de>");
349 MODULE_DESCRIPTION("MTD driver for uncached system RAM");
350