blob: dbc812dfc51e65cd351cc1af069714a5f76e5734 [file] [log] [blame]
wdenkc83bf6a2004-01-06 22:38:14 +00001/*
2 * (C) Copyright 2004
3 * Wolfgang Denk, DENX Software Engineering, wd@denx.de.
4 *
5 * See file CREDITS for list of people who contributed to this
6 * project.
7 *
8 * This program is free software; you can redistribute it and/or
9 * modify it under the terms of the GNU General Public License as
10 * published by the Free Software Foundation; either version 2 of
11 * the License, or (at your option) any later version.
12 *
13 * This program is distributed in the hope that it will be useful,
14 * but WITHOUT ANY WARRANTY; without even the implied warranty of
15 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
16 * GNU General Public License for more details.
17 *
18 * You should have received a copy of the GNU General Public License
19 * along with this program; if not, write to the Free Software
20 * Foundation, Inc., 59 Temple Place, Suite 330, Boston,
21 * MA 02111-1307 USA
22 */
23
24
25/*
26 * Check memory range for valid RAM. A simple memory test determines
27 * the actually available RAM size between addresses `base' and
28 * `base + maxsize'.
29 */
30long get_ram_size(volatile long *base, long maxsize)
31{
32 volatile long *addr;
33 long save[32];
34 long cnt;
35 long val;
36 long size;
37 int i = 0;
38
39 for (cnt = (maxsize / sizeof (long)) >> 1; cnt > 0; cnt >>= 1) {
40 addr = base + cnt; /* pointer arith! */
41 save[i++] = *addr;
42 *addr = ~cnt;
43 }
44
45 addr = base;
46 save[i] = *addr;
47 *addr = 0;
48
49 if ((val = *addr) != 0) {
50 /* Restore the original data before leaving the function.
51 */
52 *addr = save[i];
53 for (cnt = 1; cnt < maxsize / sizeof(long); cnt <<= 1) {
54 addr = base + cnt;
55 *addr = save[--i];
56 }
57 return (0);
58 }
59
60 for (cnt = 1; cnt < maxsize / sizeof (long); cnt <<= 1) {
61 addr = base + cnt; /* pointer arith! */
62 val = *addr;
63 *addr = save[--i];
64 if (val != ~cnt) {
65 size = cnt * sizeof (long);
66 /* Restore the original data before leaving the function.
67 */
68 for (cnt <<= 1; cnt < maxsize / sizeof (long); cnt <<= 1) {
69 addr = base + cnt;
70 *addr = save[--i];
71 }
72 return (size);
73 }
74 }
75
76 return (maxsize);
77}