mirror of https://github.com/dzavalishin/oskit/
97 lines
2.7 KiB
C
Executable File
97 lines
2.7 KiB
C
Executable File
/*
|
|
* Copyright (c) 1998 The University of Utah and the Flux Group.
|
|
* All rights reserved.
|
|
*
|
|
* This file is part of the Flux OSKit. The OSKit is free software, also known
|
|
* as "open source;" you can redistribute it and/or modify it under the terms
|
|
* of the GNU General Public License (GPL), version 2, as published by the Free
|
|
* Software Foundation (FSF). To explore alternate licensing terms, contact
|
|
* the University of Utah at csl-dist@cs.utah.edu or +1-801-585-3271.
|
|
*
|
|
* The OSKit 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 GPL for more details. You should have
|
|
* received a copy of the GPL along with the OSKit; see the file COPYING. If
|
|
* not, write to the FSF, 59 Temple Place #330, Boston, MA 02111-1307, USA.
|
|
*/
|
|
|
|
#include <oskit/x86/pc/rtc.h>
|
|
#include <oskit/x86/proc_reg.h>
|
|
#include <oskit/c/assert.h>
|
|
|
|
#include "boot.h"
|
|
|
|
/*
|
|
* Returns size of extended memory in kilobytes.
|
|
* Extended memory is defined to start at the 1M boundary.
|
|
*
|
|
* First ask the Real Time Clock.
|
|
* It can only tell us the truth up to 64M,
|
|
* although some max out at 63M.
|
|
* So we only believe it if it tells us less than 60M.
|
|
*
|
|
* Otherwise we probe by writing into pages starting where the RTC told us
|
|
* and stopping when they won't store.
|
|
* I.e. stopping at the first hole,
|
|
* which is usually the end of memory.
|
|
*
|
|
* XXX this assumes that the first memory hole is on a 4K boundary.
|
|
* This should be a pretty safe assumption.
|
|
*/
|
|
oskit_size_t
|
|
extended_mem_size()
|
|
{
|
|
extern unsigned long _end[];
|
|
oskit_size_t memsize;
|
|
volatile unsigned long *addr;
|
|
unsigned int old_cr0;
|
|
|
|
/*
|
|
* Try the RTC.
|
|
*/
|
|
memsize = (rtcin(RTC_DEXTHI) << 8) | rtcin(RTC_DEXTLO); /* in Kb */
|
|
if (memsize < 60*1024)
|
|
return memsize;
|
|
|
|
/*
|
|
* Try probing memory starting where the RTC reported,
|
|
* rounded down to a 4K boundary because the RTC will max at 2^16 - 1.
|
|
*/
|
|
memsize &= ~3; /* round down to 4K boundary */
|
|
|
|
/* Turn off caching. */
|
|
asm volatile("wbinvd");
|
|
old_cr0 = get_cr0();
|
|
set_cr0(old_cr0 | CR0_CD | CR0_NW);
|
|
|
|
/* Try addrs at 4K intervals until they don't store. */
|
|
addr = (unsigned long *)(memsize*1024 + 1024*1024);
|
|
assert(_end <= addr); /* avoid exotic binary tatoos */
|
|
while (1) {
|
|
*addr = 0x55555555; /* 0101... */
|
|
if (*addr != 0x55555555)
|
|
break;
|
|
|
|
*addr = 0xaaaaaaaa; /* 1010... */
|
|
if (*addr != 0xaaaaaaaa)
|
|
break;
|
|
|
|
*addr = 0xffffffff; /* 1111... */
|
|
if (*addr != 0xffffffff)
|
|
break;
|
|
|
|
*addr = 0x0; /* 0000... */
|
|
if (*addr != 0x0)
|
|
break;
|
|
|
|
addr = (unsigned long *)((oskit_size_t)addr + 4096);
|
|
}
|
|
memsize = ((oskit_size_t)addr - 1024*1024) / 1024;
|
|
|
|
/* Turn caching back on. */
|
|
set_cr0(old_cr0);
|
|
|
|
return memsize;
|
|
}
|
|
|