src/northbridge/intel/sandybridge/bootblock.c

/* SPDX-License-Identifier: GPL-2.0-only */
/* This file is part of the coreboot project. */

#include <arch/bootblock.h>
#include <device/pci_ops.h>
#include "sandybridge.h"

void bootblock_early_northbridge_init(void)
{
	uint32_t reg;

	/*
	 * The "io" variant of the config access is explicitly used to setup the
	 * PCIEXBAR because CONFIG_MMCONF_SUPPORT is set to to true. That way, all
	 * subsequent non-explicit config accesses use MCFG. This code also assumes
	 * that bootblock_northbridge_init() is the first thing called in the non-asm
	 * boot block code. The final assumption is that no assembly code is using the
	 * CONFIG_MMCONF_SUPPORT option to do PCI config accesses.
	 *
	 * The PCIEXBAR is assumed to live in the memory mapped IO space under 4GiB.
	 */
	reg = 0;
	pci_io_write_config32(HOST_BRIDGE, PCIEXBAR + 4, reg);
	reg = CONFIG_MMCONF_BASE_ADDRESS | 4 | 1; /* 64MiB - 0-63 buses. */
	pci_io_write_config32(HOST_BRIDGE, PCIEXBAR, reg);
}