LXR uboot/common/memsize.c

   1/*
   2 * (C) Copyright 2004
   3 * Wolfgang Denk, DENX Software Engineering, wd@denx.de.
   4 *
   5 * See file CREDITS for list of people who contributed to this
   6 * project.
   7 *
   8 * This program is free software; you can redistribute it and/or
   9 * modify it under the terms of the GNU General Public License as
  10 * published by the Free Software Foundation; either version 2 of
  11 * the License, or (at your option) any later version.
  12 *
  13 * This program is distributed in the hope that it will be useful,
  14 * but WITHOUT ANY WARRANTY; without even the implied warranty of
  15 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  16 * GNU General Public License for more details.
  17 *
  18 * You should have received a copy of the GNU General Public License
  19 * along with this program; if not, write to the Free Software
  20 * Foundation, Inc., 59 Temple Place, Suite 330, Boston,
  21 * MA 02111-1307 USA
  22 */
  23
  24#include <config.h>
  25#ifdef __PPC__
  26/*
  27 * At least on G2 PowerPC cores, sequential accesses to non-existent
  28 * memory must be synchronized.
  29 */
  30# include <asm/io.h>    /* for sync() */
  31#else
  32# define sync()         /* nothing */
  33#endif
  34
  35/*
  36 * Check memory range for valid RAM. A simple memory test determines
  37 * the actually available RAM size between addresses `base' and
  38 * `base + maxsize'.
  39 */
  40long get_ram_size(volatile long *base, long maxsize)
  41{
  42        volatile long *addr;
  43        long           save[32];
  44        long           cnt;
  45        long           val;
  46        long           size;
  47        int            i = 0;
  48
  49        for (cnt = (maxsize / sizeof (long)) >> 1; cnt > 0; cnt >>= 1) {
  50                addr = base + cnt;      /* pointer arith! */
  51                sync ();
  52                save[i++] = *addr;
  53                sync ();
  54                *addr = ~cnt;
  55        }
  56
  57        addr = base;
  58        sync ();
  59        save[i] = *addr;
  60        sync ();
  61        *addr = 0;
  62
  63        sync ();
  64        if ((val = *addr) != 0) {
  65                /* Restore the original data before leaving the function.
  66                 */
  67                sync ();
  68                *addr = save[i];
  69                for (cnt = 1; cnt < maxsize / sizeof(long); cnt <<= 1) {
  70                        addr  = base + cnt;
  71                        sync ();
  72                        *addr = save[--i];
  73                }
  74                return (0);
  75        }
  76
  77        for (cnt = 1; cnt < maxsize / sizeof (long); cnt <<= 1) {
  78                addr = base + cnt;      /* pointer arith! */
  79                val = *addr;
  80                *addr = save[--i];
  81                if (val != ~cnt) {
  82                        size = cnt * sizeof (long);
  83                        /* Restore the original data before leaving the function.
  84                         */
  85                        for (cnt <<= 1; cnt < maxsize / sizeof (long); cnt <<= 1) {
  86                                addr  = base + cnt;
  87                                *addr = save[--i];
  88                        }
  89                        return (size);
  90                }
  91        }
  92
  93        return (maxsize);
  94}
  95