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[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                  */
  54                 sync ();
  55                 *addr = save[i];
  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                         /* Restore the original data before leaving the function.
  71                          */
  72                         for (cnt <<= 1; cnt < maxsize / sizeof (long); cnt <<= 1) {
  73                                 addr  = base + cnt;
  74                                 *addr = save[--i];
  75                         }
  76                         return (size);
  77                 }
  78         }
  79
  80         return (maxsize);
  81 }
  82
  83 phys_size_t __weak get_effective_memsize(void)
  84 {
  85 #ifndef CONFIG_VERY_BIG_RAM
  86         return gd->ram_size;
  87 #else
  88         /* limit stack to what we can reasonable map */
  89         return ((gd->ram_size > CONFIG_MAX_MEM_MAPPED) ?
  90                 CONFIG_MAX_MEM_MAPPED : gd->ram_size);
  91 #endif
  92 }