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                 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 }