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/*
* This file is part of the coreboot project.
*
* Copyright (C) 2017 Keith Hui <buurin@gmail.com>
*
* 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.
*/
#define __SIMPLE_DEVICE__
#include <arch/io.h>
#include <cbmem.h>
#include <commonlib/helpers.h>
#include "i440bx.h"
void *cbmem_top(void)
{
/* Base of TSEG is top of usable DRAM */
/*
* SMRAM - System Management RAM Control Register
* 0x72
* [7:4] Not relevant to this function.
* [3:3] Global SMRAM Enable (G_SMRAME)
* [2:0] Hardwired to 010.
*
* ESMRAMC - Extended System Management RAM Control
* 0x73
* [7:7] H_SMRAM_EN
* 1 = When G_SMRAME=1, High SMRAM space is enabled at
* 0x100A0000-0x100FFFFF and forwarded to DRAM address
* 0x000A0000-0x000FFFFF.
* 0 = When G_SMRAME=1, Compatible SMRAM space is enabled at
* 0x000A0000-0x000BFFFF.
* [6:3] Not relevant to this function.
* [2:1] TSEG Size (T_SZ)
* Selects the size of the TSEG memory block, if enabled.
* 00 = 128KiB
* 01 = 256KiB
* 10 = 512KiB
* 11 = 1MiB
* [0:0] TSEG_EN
* When SMRAM[G_SMRAME] and this bit are 1, TSEG is enabled to
* appear between DRAM address (TOM-<TSEG Size>) to TOM.
*
* Source: 440BX datasheet, pages 3-28 thru 3-29.
*/
unsigned long tom = pci_read_config8(NB, DRB7) * 8 * MiB;
int gsmrame = pci_read_config8(NB, SMRAM) & 0x8;
/* T_SZ and TSEG_EN */
int tseg = pci_read_config8(NB, ESMRAMC) & 0x7;
if ((tseg & 0x1) && gsmrame) {
int tseg_size = 128 * KiB * (1 << (tseg >> 1));
tom -= tseg_size;
}
return (void *)tom;
}
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