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 *addr = ~cnt; 42 } 43 44 addr = base; 45 sync(); 46 save[i] = *addr; 47 sync(); 48 *addr = 0; 49 50 sync(); 51 if ((val = *addr) != 0) { 52 /* Restore the original data before leaving the function. */ 53 sync(); 54 *addr = save[i]; 55 for (cnt = 1; cnt < maxsize / sizeof(long); cnt <<= 1) { 56 addr = base + cnt; 57 sync(); 58 *addr = save[--i]; 59 } 60 return (0); 61 } 62 63 for (cnt = 1; cnt < maxsize / sizeof(long); cnt <<= 1) { 64 addr = base + cnt; /* pointer arith! */ 65 val = *addr; 66 *addr = save[--i]; 67 if (val != ~cnt) { 68 size = cnt * sizeof(long); 69 /* 70 * Restore the original data 71 * before leaving the function. 72 */ 73 for (cnt <<= 1; 74 cnt < maxsize / sizeof(long); 75 cnt <<= 1) { 76 addr = base + cnt; 77 *addr = save[--i]; 78 } 79 return (size); 80 } 81 } 82 83 return (maxsize); 84 } 85 86 phys_size_t __weak get_effective_memsize(void) 87 { 88 #ifndef CONFIG_VERY_BIG_RAM 89 return gd->ram_size; 90 #else 91 /* limit stack to what we can reasonable map */ 92 return ((gd->ram_size > CONFIG_MAX_MEM_MAPPED) ? 93 CONFIG_MAX_MEM_MAPPED : gd->ram_size); 94 #endif 95 } 96