| wdenk | 87249ba | 2004-01-06 22:38:14 +0000 | [diff] [blame] | 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 | } |