linux/arch/x86/kernel/aperture_64.c

/*
 * Firmware replacement code.
 *
 * Work around broken BIOSes that don't set an aperture or only set the
 * aperture in the AGP bridge.
 * If all fails map the aperture over some low memory.  This is cheaper than
 * doing bounce buffering. The memory is lost. This is done at early boot
 * because only the bootmem allocator can allocate 32+MB.
 *
 * Copyright 2002 Andi Kleen, SuSE Labs.
 */
#include <linux/kernel.h>
#include <linux/types.h>
#include <linux/init.h>
#include <linux/bootmem.h>
#include <linux/mmzone.h>
#include <linux/pci_ids.h>
#include <linux/pci.h>
#include <linux/bitops.h>
#include <linux/ioport.h>
#include <asm/e820.h>
#include <asm/io.h>
#include <asm/gart.h>
#include <asm/pci-direct.h>
#include <asm/dma.h>
#include <asm/k8.h>

int gart_iommu_aperture;
int gart_iommu_aperture_disabled __initdata = 0;
int gart_iommu_aperture_allowed __initdata = 0;

int fallback_aper_order __initdata = 1; /* 64MB */
int fallback_aper_force __initdata = 0;

int fix_aperture __initdata = 1;

static struct resource gart_resource = {
	.name	= "GART",
	.flags	= IORESOURCE_MEM,
};

static void __init insert_aperture_resource(u32 aper_base, u32 aper_size)
{
	gart_resource.start = aper_base;
	gart_resource.end = aper_base + aper_size - 1;
	insert_resource(&iomem_resource, &gart_resource);
}

/* This code runs before the PCI subsystem is initialized, so just
   access the northbridge directly. */

static u32 __init allocate_aperture(void)
{
	u32 aper_size;
	void *p;

	if (fallback_aper_order > 7)
		fallback_aper_order = 7;
	aper_size = (32 * 1024 * 1024) << fallback_aper_order;

	/*
	 * Aperture has to be naturally aligned. This means a 2GB aperture
	 * won't have much chance of finding a place in the lower 4GB of
	 * memory. Unfortunately we cannot move it up because that would
	 * make the IOMMU useless.
	 */
	p = __alloc_bootmem_nopanic(aper_size, aper_size, 0);
	if (!p || __pa(p)+aper_size > 0xffffffff) {
		printk("Cannot allocate aperture memory hole (%p,%uK)\n",
		       p, aper_size>>10);
		if (p)
			free_bootmem(__pa(p), aper_size);
		return 0;
	}
	printk("Mapping aperture over %d KB of RAM @ %lx\n",
	       aper_size >> 10, __pa(p));
	insert_aperture_resource((u32)__pa(p), aper_size);

	return (u32)__pa(p);
}

static int __init aperture_valid(u64 aper_base, u32 aper_size)
{
	if (!aper_base)
		return 0;
	if (aper_size < 64*1024*1024) {
		printk("Aperture too small (%d MB)\n", aper_size>>20);
		return 0;
	}
	if (aper_base + aper_size > 0x100000000UL) {
		printk("Aperture beyond 4GB. Ignoring.\n");
		return 0;
	}
	if (e820_any_mapped(aper_base, aper_base + aper_size, E820_RAM)) {
		printk("Aperture pointing to e820 RAM. Ignoring.\n");
		return 0;
	}
	return 1;
}

/* Find a PCI capability */
static __u32 __init find_cap(int num, int slot, int func, int cap)
{
	int bytes;
	u8 pos;

	if (!(read_pci_config_16(num, slot, func, PCI_STATUS) &
						PCI_STATUS_CAP_LIST))
		return 0;

	pos = read_pci_config_byte(num, slot, func, PCI_CAPABILITY_LIST);
	for (bytes = 0; bytes < 48 && pos >= 0x40; bytes++) {
		u8 id;

		pos &= ~3;
		id = read_pci_config_byte(num, slot, func, pos+PCI_CAP_LIST_ID);
		if (id == 0xff)
			break;
		if (id == cap)
			return pos;
		pos = read_pci_config_byte(num, slot, func,
						pos+PCI_CAP_LIST_NEXT);
	}
	return 0;
}

/* Read a standard AGPv3 bridge header */
static __u32 __init read_agp(int num, int slot, int func, int cap, u32 *order)
{
	u32 apsize;
	u32 apsizereg;
	int nbits;
	u32 aper_low, aper_hi;
	u64 aper;

	printk("AGP bridge at %02x:%02x:%02x\n", num, slot, func);
	apsizereg = read_pci_config_16(num, slot, func, cap + 0x14);
	if (apsizereg == 0xffffffff) {
		printk("APSIZE in AGP bridge unreadable\n");
		return 0;
	}

	apsize = apsizereg & 0xfff;
	/* Some BIOS use weird encodings not in the AGPv3 table. */
	if (apsize & 0xff)
		apsize |= 0xf00;
	nbits = hweight16(apsize);
	*order = 7 - nbits;
	if ((int)*order < 0) /* < 32MB */
		*order = 0;

	aper_low = read_pci_config(num, slot, func, 0x10);
	aper_hi = read_pci_config(num, slot, func, 0x14);
	aper = (aper_low & ~((1<<22)-1)) | ((u64)aper_hi << 32);

	printk("Aperture from AGP @ %Lx size %u MB (APSIZE %x)\n",
	       aper, 32 << *order, apsizereg);

	if (!aperture_valid(aper, (32*1024*1024) << *order))
		return 0;
	return (u32)aper;
}

/*
 * Look for an AGP bridge. Windows only expects the aperture in the
 * AGP bridge and some BIOS forget to initialize the Northbridge too.
 * Work around this here.
 *
 * Do an PCI bus scan by hand because we're running before the PCI
 * subsystem.
 *
 * All K8 AGP bridges are AGPv3 compliant, so we can do this scan
 * generically. It's probably overkill to always scan all slots because
 * the AGP bridges should be always an own bus on the HT hierarchy,
 * but do it here for future safety.
 */
static __u32 __init search_agp_bridge(u32 *order, int *valid_agp)
{
	int num, slot, func;

	/* Poor man's PCI discovery */
	for (num = 0; num < 256; num++) {
		for (slot = 0; slot < 32; slot++) {
			for (func = 0; func < 8; func++) {
				u32 class, cap;
				u8 type;
				class = read_pci_config(num, slot, func,
							PCI_CLASS_REVISION);
				if (class == 0xffffffff)
					break;

				switch (class >> 16) {
				case PCI_CLASS_BRIDGE_HOST:
				case PCI_CLASS_BRIDGE_OTHER: /* needed? */
					/* AGP bridge? */
					cap = find_cap(num, slot, func,
							PCI_CAP_ID_AGP);
					if (!cap)
						break;
					*valid_agp = 1;
					return read_agp(num, slot, func, cap,
							order);
				}

				/* No multi-function device? */
				type = read_pci_config_byte(num, slot, func,
							       PCI_HEADER_TYPE);
				if (!(type & 0x80))
					break;
			}
		}
	}
	printk("No AGP bridge found\n");

	return 0;
}

void __init gart_iommu_hole_init(void)
{
	u32 aper_size, aper_alloc = 0, aper_order = 0, last_aper_order = 0;
	u64 aper_base, last_aper_base = 0;
	int fix, num, valid_agp = 0;

	if (gart_iommu_aperture_disabled || !fix_aperture ||
	    !early_pci_allowed())
		return;

	printk(KERN_INFO  "Checking aperture...\n");

	fix = 0;
	for (num = 24; num < 32; num++) {
		if (!early_is_k8_nb(read_pci_config(0, num, 3, 0x00)))
			continue;

		iommu_detected = 1;
		gart_iommu_aperture = 1;

		aper_order = (read_pci_config(0, num, 3, 0x90) >> 1) & 7;
		aper_size = (32 * 1024 * 1024) << aper_order;
		aper_base = read_pci_config(0, num, 3, 0x94) & 0x7fff;
		aper_base <<= 25;

		printk("CPU %d: aperture @ %Lx size %u MB\n", num-24,
		       aper_base, aper_size>>20);

		if (!aperture_valid(aper_base, aper_size)) {
			fix = 1;
			break;
		}

		if ((last_aper_order && aper_order != last_aper_order) ||
		    (last_aper_base && aper_base != last_aper_base)) {
			fix = 1;
			break;
		}
		last_aper_order = aper_order;
		last_aper_base = aper_base;
	}

	if (!fix && !fallback_aper_force) {
		if (last_aper_base) {
			unsigned long n = (32 * 1024 * 1024) << last_aper_order;

			insert_aperture_resource((u32)last_aper_base, n);
		}
		return;
	}

	if (!fallback_aper_force)
		aper_alloc = search_agp_bridge(&aper_order, &valid_agp);

	if (aper_alloc) {
		/* Got the aperture from the AGP bridge */
	} else if (swiotlb && !valid_agp) {
		/* Do nothing */
	} else if ((!no_iommu && end_pfn > MAX_DMA32_PFN) ||
		   force_iommu ||
		   valid_agp ||
		   fallback_aper_force) {
		printk("Your BIOS doesn't leave a aperture memory hole\n");
		printk("Please enable the IOMMU option in the BIOS setup\n");
		printk("This costs you %d MB of RAM\n",
		       32 << fallback_aper_order);

		aper_order = fallback_aper_order;
		aper_alloc = allocate_aperture();
		if (!aper_alloc) {
			/*
			 * Could disable AGP and IOMMU here, but it's
			 * probably not worth it. But the later users
			 * cannot deal with bad apertures and turning
			 * on the aperture over memory causes very
			 * strange problems, so it's better to panic
			 * early.
			 */
			panic("Not enough memory for aperture");
		}
	} else {
		return;
	}

	/* Fix up the north bridges */
	for (num = 24; num < 32; num++) {
		if (!early_is_k8_nb(read_pci_config(0, num, 3, 0x00)))
			continue;

		/*
		 * Don't enable translation yet. That is done later.
		 * Assume this BIOS didn't initialise the GART so
		 * just overwrite all previous bits
		 */
		write_pci_config(0, num, 3, 0x90, aper_order<<1);
		write_pci_config(0, num, 3, 0x94, aper_alloc>>25);
	}
}