linux/arch/x86_64/kernel/early-quirks.c

/* Various workarounds for chipset bugs.
   This code runs very early and can't use the regular PCI subsystem
   The entries are keyed to PCI bridges which usually identify chipsets
   uniquely.
   This is only for whole classes of chipsets with specific problems which
   need early invasive action (e.g. before the timers are initialized).
   Most PCI device specific workarounds can be done later and should be
   in standard PCI quirks
   Mainboard specific bugs should be handled by DMI entries.
   CPU specific bugs in setup.c */

#include <linux/pci.h>
#include <linux/acpi.h>
#include <linux/pci_ids.h>
#include <asm/pci-direct.h>
#include <asm/proto.h>
#include <asm/dma.h>

static void via_bugs(void)
{
#ifdef CONFIG_IOMMU
	if ((end_pfn > MAX_DMA32_PFN ||  force_iommu) &&
	    !iommu_aperture_allowed) {
		printk(KERN_INFO
  "Looks like a VIA chipset. Disabling IOMMU. Override with iommu=allowed\n");
		iommu_aperture_disabled = 1;
	}
#endif
}

#ifdef CONFIG_ACPI

static int nvidia_hpet_detected __initdata;

static int __init nvidia_hpet_check(unsigned long phys, unsigned long size)
{
	nvidia_hpet_detected = 1;
	return 0;
}
#endif

static void nvidia_bugs(void)
{
#ifdef CONFIG_ACPI
	/*
	 * All timer overrides on Nvidia are
	 * wrong unless HPET is enabled.
	 */
	nvidia_hpet_detected = 0;
	acpi_table_parse(ACPI_HPET, nvidia_hpet_check);
	if (nvidia_hpet_detected == 0) {
		acpi_skip_timer_override = 1;
		printk(KERN_INFO "Nvidia board "
		       "detected. Ignoring ACPI "
		       "timer override.\n");
	}
#endif
	/* RED-PEN skip them on mptables too? */

}

static void ati_bugs(void)
{
#if 1 /* for testing */
	printk("ATI board detected\n");
#endif
	/* No bugs right now */
}

struct chipset {
	u16 vendor;
	void (*f)(void);
};

static struct chipset early_qrk[] = {
	{ PCI_VENDOR_ID_NVIDIA, nvidia_bugs },
	{ PCI_VENDOR_ID_VIA, via_bugs },
	{ PCI_VENDOR_ID_ATI, ati_bugs },
	{}
};

void __init early_quirks(void)
{
	int num, slot, func;

	if (!early_pci_allowed())
		return;

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

		       		if ((class >> 16) != PCI_CLASS_BRIDGE_PCI)
					continue;

				vendor = read_pci_config(num, slot, func,
							 PCI_VENDOR_ID);
				vendor &= 0xffff;

				for (i = 0; early_qrk[i].f; i++)
					if (early_qrk[i].vendor == vendor) {
						early_qrk[i].f();
						return;
					}

				type = read_pci_config_byte(num, slot, func,
							    PCI_HEADER_TYPE);
				if (!(type & 0x80))
					break;
			}
		}
	}
}