src/northbridge/intel/gm45/ram_calc.c

/*
 * This file is part of the coreboot project.
 *
 * Copyright (C) 2012 secunet Security Networks AG
 *
 * 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.
 */

// Use simple device model for this file even in ramstage
#define __SIMPLE_DEVICE__

#include <stdint.h>
#include <arch/io.h>
#include <device/pci_def.h>
#include <console/console.h>
#include <cpu/intel/romstage.h>
#include <cbmem.h>
#include "gm45.h"

/*
 * Decodes used Graphics Mode Select (GMS) to kilobytes.
 * The options for 1M, 4M, 8M and 16M preallocated igd memory are
 * undocumented but are verified to work.
 */
u32 decode_igd_memory_size(const u32 gms)
{
	static const u16 ggc2uma[] = { 0, 1, 4, 8, 16, 32, 48, 64, 128, 256,
				       96, 160, 224, 352 };

	if (gms > ARRAY_SIZE(ggc2uma))
		die("Bad Graphics Mode Select (GMS) setting.\n");

	return ggc2uma[gms] << 10;
}

/** Decodes used Graphics Stolen Memory (GSM) to kilobytes. */
u32 decode_igd_gtt_size(const u32 gsm)
{
	switch (gsm) {
	case 0:
		return 0 << 10;
	case 1:
		return 1 << 10;
	case 3:
	case 9:
		return 2 << 10;
	case 10:
		return 3 << 10;
	case 11:
		return 4 << 10;
	default:
		die("Bad Graphics Stolen Memory (GSM) setting.\n");
		return 0;
	}
}

static uintptr_t smm_region_start(void)
{
	const pci_devfn_t dev = PCI_DEV(0, 0, 0);

	u32 tor;

	/* Top of Lower Usable DRAM */
	tor = (pci_read_config16(dev, D0F0_TOLUD) & 0xfff0) << 16;

	/* Graphics memory comes next */
	const u32 ggc = pci_read_config16(dev, D0F0_GGC);
	if (!(ggc & 2)) {
		/* Graphics memory */
		tor -= decode_igd_memory_size((ggc >> 4) & 0xf) << 10;
		/* GTT Graphics Stolen Memory Size (GGMS) */
		tor -= decode_igd_gtt_size((ggc >> 8) & 0xf) << 10;
	}
	return tor;
}

/* Depending of UMA and TSEG configuration, TSEG might start at any
 * 1 MiB aligment. As this may cause very greedy MTRR setup, push
 * CBMEM top downwards to 4 MiB boundary.
 */
void *cbmem_top(void)
{
	uintptr_t top_of_ram = ALIGN_DOWN(smm_region_start(), 4*MiB);
	return (void *) top_of_ram;
}

void *setup_stack_and_mtrrs(void)
{
	return (void*)CONFIG_RAMTOP;
}