/*  * Firmware replacement code. *  * Work around broken BIOSes that don't set an aperture.  * The IOMMU code needs an aperture even who no AGP is present in the system. * 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. * $Id: aperture.c,v 1.4 2002/11/28 06:05:58 ak Exp $ */#include <linux/config.h>#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 <asm/e820.h>#include <asm/io.h>#include <asm/proto.h>#include <asm/pci-direct.h>int fallback_aper_order __initdata = 1; /* 64MB */int fallback_aper_force __initdata = 0; extern int no_iommu, force_mmu;/* This code runs before the PCI subsystem is initialized, so just    access the northbridge directly. */#define NB_ID_3 (PCI_VENDOR_ID_AMD | (0x1103<<16))static u32 __init allocate_aperture(void) {#ifdef CONFIG_DISCONTIGMEM	pg_data_t *nd0 = NODE_DATA(0);#else	pg_data_t *nd0 = &contig_page_data;#endif		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 an 2GB aperture won't          * have much chances to find a place in the lower 4GB of memory. Unfortunately          * we cannot move it up because that would make the IOMMU useless.	 */	p = __alloc_bootmem_node(nd0, 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_generic((unsigned long)p, aper_size); 		return 0;	}	printk("Mapping aperture over %d KB of RAM @ %lx\n",  	       aper_size >> 10, __pa(p)); 	return (u32)__pa(p); }void __init iommu_hole_init(void) { 	int fix, num; 	u32 aper_size, aper_alloc, aper_order;	u64 aper_base; 	if (no_iommu)		return;	if (end_pfn < (0xffffffff>>PAGE_SHIFT) && !force_mmu) 		return;	printk("Checking aperture...\n"); 	fix = 0;	for (num = 24; num < 32; num++) {				if (read_pci_config(0, num, 3, 0x00) != NB_ID_3) 			continue;			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 KB\n", num-24, 		       aper_base, aper_size>>10);		if (!aper_base || aper_base + aper_size >= 0xffffffff) {			fix = 1; 			break; 		} 				if (e820_mapped(aper_base, aper_base + aper_size, E820_RAM)) {  			printk("Aperture pointing to e820 RAM. Ignoring.\n");			fix = 1; 			break; 		} 	} 	if (!fix && !fallback_aper_force) 		return; 	printk("Your BIOS doesn't leave a aperture memory hole\n");	printk("Please enable the IOMMU option in the BIOS setup\n"); 	aper_alloc = allocate_aperture(); 	if (!aper_alloc) 		return; 	for (num = 24; num < 32; num++) { 				if (read_pci_config(0, num, 3, 0x00) != NB_ID_3) 			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, fallback_aper_order<<1); 		write_pci_config(0, num, 3, 0x94, aper_alloc>>25); 	} }