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c83bf6a2 WD |
1 | /* |
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 | */ | |
30 | long 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 | } |