common/memsize.c

   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[31];
  31         long           save_base;
  32         long           cnt;
  33         long           val;
  34         long           size;
  35         int            i = 0;
  36
  37         for (cnt = (maxsize / sizeof(long)) >> 1; cnt > 0; cnt >>= 1) {
  38                 addr = base + cnt;      /* pointer arith! */
  39                 sync();
  40                 save[i++] = *addr;
  41                 sync();
  42                 *addr = ~cnt;
  43         }
  44
  45         addr = base;
  46         sync();
  47         save_base = *addr;
  48         sync();
  49         *addr = 0;
  50
  51         sync();
  52         if ((val = *addr) != 0) {
  53                 /* Restore the original data before leaving the function. */
  54                 sync();
  55                 *base = save_base;
  56                 for (cnt = 1; cnt < maxsize / sizeof(long); cnt <<= 1) {
  57                         addr  = base + cnt;
  58                         sync();
  59                         *addr = save[--i];
  60                 }
  61                 return (0);
  62         }
  63
  64         for (cnt = 1; cnt < maxsize / sizeof(long); cnt <<= 1) {
  65                 addr = base + cnt;      /* pointer arith! */
  66                 val = *addr;
  67                 *addr = save[--i];
  68                 if (val != ~cnt) {
  69                         size = cnt * sizeof(long);
  70                         /*
  71                          * Restore the original data
  72                          * before leaving the function.
  73                          */
  74                         for (cnt <<= 1;
  75                              cnt < maxsize / sizeof(long);
  76                              cnt <<= 1) {
  77                                 addr  = base + cnt;
  78                                 *addr = save[--i];
  79                         }
  80                         return (size);
  81                 }
  82         }
  83
  84         return (maxsize);
  85 }
  86
  87 phys_size_t __weak get_effective_memsize(void)
  88 {
  89 #ifndef CONFIG_VERY_BIG_RAM
  90         return gd->ram_size;
  91 #else
  92         /* limit stack to what we can reasonable map */
  93         return ((gd->ram_size > CONFIG_MAX_MEM_MAPPED) ?
  94                 CONFIG_MAX_MEM_MAPPED : gd->ram_size);
  95 #endif
  96 }