1 // SPDX-License-Identifier: GPL-2.0+ 2 /* 3 * (C) Copyright 2004 4 * Wolfgang Denk, DENX Software Engineering, wd@denx.de. 5 */ 6 7 #include <common.h> 8 9 DECLARE_GLOBAL_DATA_PTR; 10 11 #ifdef __PPC__ 12 /* 13 * At least on G2 PowerPC cores, sequential accesses to non-existent 14 * memory must be synchronized. 15 */ 16 # include <asm/io.h> /* for sync() */ 17 #else 18 # define sync() /* nothing */ 19 #endif 20 21 /* 22 * Check memory range for valid RAM. A simple memory test determines 23 * the actually available RAM size between addresses `base' and 24 * `base + maxsize'. 25 */ 26 long get_ram_size(long *base, long maxsize) 27 { 28 volatile long *addr; 29 long save[31]; 30 long save_base; 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_base = *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 *base = save_base; 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 /* warning: don't restore save_base in this case, 80 * it is already done in the loop because 81 * base and base+size share the same physical memory 82 * and *base is saved after *(base+size) modification 83 * in first loop 84 */ 85 return (size); 86 } 87 } 88 *base = save_base; 89 90 return (maxsize); 91 } 92 93 phys_size_t __weak get_effective_memsize(void) 94 { 95 #ifndef CONFIG_VERY_BIG_RAM 96 return gd->ram_size; 97 #else 98 /* limit stack to what we can reasonable map */ 99 return ((gd->ram_size > CONFIG_MAX_MEM_MAPPED) ? 100 CONFIG_MAX_MEM_MAPPED : gd->ram_size); 101 #endif 102 } 103