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/*
* (C) Copyright 2004
* Wolfgang Denk, DENX Software Engineering, wd@denx.de.
*
* See file CREDITS for list of people who contributed to this
* project.
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License as
* published by the Free Software Foundation; either version 2 of
* the License, or (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 59 Temple Place, Suite 330, Boston,
* MA 02111-1307 USA
*/
#include <config.h>
#ifdef __PPC__
/*
* At least on G2 PowerPC cores, sequential accesses to non-existent
* memory must be synchronized.
*/
# include <asm/io.h> /* for sync() */
#else
# define sync() /* nothing */
#endif
/*
* Check memory range for valid RAM. A simple memory test determines
* the actually available RAM size between addresses `base' and
* `base + maxsize'.
*/
long get_ram_size(long *base, long maxsize)
{
volatile long *addr;
long save[32];
long cnt;
long val;
long size;
int i = 0;
for (cnt = (maxsize / sizeof (long)) >> 1; cnt > 0; cnt >>= 1) {
addr = base + cnt; /* pointer arith! */
sync ();
save[i++] = *addr;
sync ();
*addr = ~cnt;
}
addr = base;
sync ();
save[i] = *addr;
sync ();
*addr = 0;
sync ();
if ((val = *addr) != 0) {
/* Restore the original data before leaving the function.
*/
sync ();
*addr = save[i];
for (cnt = 1; cnt < maxsize / sizeof(long); cnt <<= 1) {
addr = base + cnt;
sync ();
*addr = save[--i];
}
return (0);
}
for (cnt = 1; cnt < maxsize / sizeof (long); cnt <<= 1) {
addr = base + cnt; /* pointer arith! */
val = *addr;
*addr = save[--i];
if (val != ~cnt) {
size = cnt * sizeof (long);
/* Restore the original data before leaving the function.
*/
for (cnt <<= 1; cnt < maxsize / sizeof (long); cnt <<= 1) {
addr = base + cnt;
*addr = save[--i];
}
return (size);
}
}
return (maxsize);
}
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