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 } 78