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/*
* This file is part of the coreboot 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; version 2 of the License.
*
* 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.
*/
#include <stddef.h>
#include <cbmem.h>
#include <symbols.h>
#include <arch/io.h>
#include "mainboard.h"
#define PATTERN1 0x55
#define PATTERN2 0xaa
/* Returns 1 if mebibyte mb is present and 0 otherwise. */
static int probe_mb(int mb)
{
char *ptr = (char *) 0x60000000 + (mb << 20) + 0xfffff;
char old;
if (ptr < (char *) &_eprogram) {
/* Don't probe below _end to avoid accidentally clobering
oneself. */
return 1;
}
old = read8(ptr);
write8(ptr, PATTERN1);
if (read8(ptr) != PATTERN1)
return 0;
write8(ptr, PATTERN2);
if (read8(ptr) != PATTERN2)
return 0;
write8(ptr, old);
return 1;
}
int probe_ramsize(void)
{
int i;
int discovered = 0;
static int saved_result;
if (saved_result)
return saved_result;
/* Compact binary search. */
/* 1 GiB is the largest supported RAM by this machine. */
for (i = 9; i >= 0; i--)
if (probe_mb(discovered | (1 << i)))
discovered |= (1 << i);
discovered++;
saved_result = discovered;
return discovered;
}
void *cbmem_top(void)
{
return _dram + (probe_ramsize() << 20);
}
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