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 #include <config.h> 25 #ifdef __PPC__ 26 /* 27 * At least on G2 PowerPC cores, sequential accesses to non-existent 28 * memory must be synchronized. 29 */ 30 # include <asm/io.h> /* for sync() */ 31 #else 32 # define sync() /* nothing */ 33 #endif 34 35 /* 36 * Check memory range for valid RAM. A simple memory test determines 37 * the actually available RAM size between addresses `base' and 38 * `base + maxsize'. 39 */ 40 long get_ram_size(volatile long *base, long maxsize) 41 { 42 volatile long *addr; 43 long save[32]; 44 long cnt; 45 long val; 46 long size; 47 int i = 0; 48 49 for (cnt = (maxsize / sizeof (long)) >> 1; cnt > 0; cnt >>= 1) { 50 addr = base + cnt; /* pointer arith! */ 51 sync (); 52 save[i++] = *addr; 53 sync (); 54 *addr = ~cnt; 55 } 56 57 addr = base; 58 sync (); 59 save[i] = *addr; 60 sync (); 61 *addr = 0; 62 63 sync (); 64 if ((val = *addr) != 0) { 65 /* Restore the original data before leaving the function. 66 */ 67 sync (); 68 *addr = save[i]; 69 for (cnt = 1; cnt < maxsize / sizeof(long); cnt <<= 1) { 70 addr = base + cnt; 71 sync (); 72 *addr = save[--i]; 73 } 74 return (0); 75 } 76 77 for (cnt = 1; cnt < maxsize / sizeof (long); cnt <<= 1) { 78 addr = base + cnt; /* pointer arith! */ 79 val = *addr; 80 *addr = save[--i]; 81 if (val != ~cnt) { 82 size = cnt * sizeof (long); 83 /* Restore the original data before leaving the function. 84 */ 85 for (cnt <<= 1; cnt < maxsize / sizeof (long); cnt <<= 1) { 86 addr = base + cnt; 87 *addr = save[--i]; 88 } 89 return (size); 90 } 91 } 92 93 return (maxsize); 94 } 95