1 /* 2 * (C) Copyright 2004 3 * Wolfgang Denk, DENX Software Engineering, wd@denx.de. 4 * 5 * SPDX-License-Identifier: GPL-2.0+ 6 */ 7 8 #include <common.h> 9 10 DECLARE_GLOBAL_DATA_PTR; 11 12 #ifdef __PPC__ 13 /* 14 * At least on G2 PowerPC cores, sequential accesses to non-existent 15 * memory must be synchronized. 16 */ 17 # include <asm/io.h> /* for sync() */ 18 #else 19 # define sync() /* nothing */ 20 #endif 21 22 /* 23 * Check memory range for valid RAM. A simple memory test determines 24 * the actually available RAM size between addresses `base' and 25 * `base + maxsize'. 26 */ 27 long get_ram_size(long *base, long maxsize) 28 { 29 volatile long *addr; 30 long save[32]; 31 long cnt; 32 long val; 33 long size; 34 int i = 0; 35 36 for (cnt = (maxsize / sizeof(long)) >> 1; cnt >= 0; cnt >>= 1) { 37 addr = base + cnt; /* pointer arith! */ 38 sync(); 39 save[i] = *addr; 40 sync(); 41 if (cnt) { 42 i++; 43 *addr = ~cnt; 44 } else { 45 *addr = 0; 46 } 47 } 48 49 sync(); 50 cnt = 0; 51 do { 52 addr = base + cnt; /* pointer arith! */ 53 val = *addr; 54 *addr = save[i--]; 55 sync(); 56 if (((cnt == 0) && (val != 0)) || 57 ((cnt != 0) && (val != ~cnt))) { 58 size = cnt * sizeof(long); 59 /* 60 * Restore the original data 61 * before leaving the function. 62 */ 63 for (cnt <<= 1; 64 cnt < maxsize / sizeof(long); 65 cnt <<= 1) { 66 addr = base + cnt; 67 *addr = save[i--]; 68 } 69 return (size); 70 } 71 72 if (cnt) 73 cnt = cnt << 1; 74 else 75 cnt = 1; 76 } while (cnt < maxsize / sizeof(long)); 77 78 return (maxsize); 79 } 80 81 phys_size_t __weak get_effective_memsize(void) 82 { 83 #ifndef CONFIG_VERY_BIG_RAM 84 return gd->ram_size; 85 #else 86 /* limit stack to what we can reasonable map */ 87 return ((gd->ram_size > CONFIG_MAX_MEM_MAPPED) ? 88 CONFIG_MAX_MEM_MAPPED : gd->ram_size); 89 #endif 90 } 91