1 files changed, 842 insertions, 0 deletions

diff --git a/arch/x86/kernel/amd_gart_64.c b/arch/x86/kernel/amd_gart_64.c
new file mode 100644
index 000000000..19a0207e5
--- /dev/null
+++ b/arch/x86/kernel/amd_gart_64.c
@@ -0,0 +1,842 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Dynamic DMA mapping support for AMD Hammer.
+ *
+ * Use the integrated AGP GART in the Hammer northbridge as an IOMMU for PCI.
+ * This allows to use PCI devices that only support 32bit addresses on systems
+ * with more than 4GB.
+ *
+ * See Documentation/core-api/dma-api-howto.rst for the interface specification.
+ *
+ * Copyright 2002 Andi Kleen, SuSE Labs.
+ */
+
+#include <linux/types.h>
+#include <linux/ctype.h>
+#include <linux/agp_backend.h>
+#include <linux/init.h>
+#include <linux/mm.h>
+#include <linux/sched.h>
+#include <linux/sched/debug.h>
+#include <linux/string.h>
+#include <linux/spinlock.h>
+#include <linux/pci.h>
+#include <linux/topology.h>
+#include <linux/interrupt.h>
+#include <linux/bitmap.h>
+#include <linux/kdebug.h>
+#include <linux/scatterlist.h>
+#include <linux/iommu-helper.h>
+#include <linux/syscore_ops.h>
+#include <linux/io.h>
+#include <linux/gfp.h>
+#include <linux/atomic.h>
+#include <linux/dma-direct.h>
+#include <linux/dma-map-ops.h>
+#include <asm/mtrr.h>
+#include <asm/proto.h>
+#include <asm/iommu.h>
+#include <asm/gart.h>
+#include <asm/set_memory.h>
+#include <asm/dma.h>
+#include <asm/amd_nb.h>
+#include <asm/x86_init.h>
+
+static unsigned long iommu_bus_base;	/* GART remapping area (physical) */
+static unsigned long iommu_size;	/* size of remapping area bytes */
+static unsigned long iommu_pages;	/* .. and in pages */
+
+static u32 *iommu_gatt_base;		/* Remapping table */
+
+/*
+ * If this is disabled the IOMMU will use an optimized flushing strategy
+ * of only flushing when an mapping is reused. With it true the GART is
+ * flushed for every mapping. Problem is that doing the lazy flush seems
+ * to trigger bugs with some popular PCI cards, in particular 3ware (but
+ * has been also seen with Qlogic at least).
+ */
+static int iommu_fullflush = 1;
+
+/* Allocation bitmap for the remapping area: */
+static DEFINE_SPINLOCK(iommu_bitmap_lock);
+/* Guarded by iommu_bitmap_lock: */
+static unsigned long *iommu_gart_bitmap;
+
+static u32 gart_unmapped_entry;
+
+#define GPTE_VALID    1
+#define GPTE_COHERENT 2
+#define GPTE_ENCODE(x) \
+	(((x) & 0xfffff000) | (((x) >> 32) << 4) | GPTE_VALID | GPTE_COHERENT)
+#define GPTE_DECODE(x) (((x) & 0xfffff000) | (((u64)(x) & 0xff0) << 28))
+
+#ifdef CONFIG_AGP
+#define AGPEXTERN extern
+#else
+#define AGPEXTERN
+#endif
+
+/* GART can only remap to physical addresses < 1TB */
+#define GART_MAX_PHYS_ADDR	(1ULL << 40)
+
+/* backdoor interface to AGP driver */
+AGPEXTERN int agp_memory_reserved;
+AGPEXTERN __u32 *agp_gatt_table;
+
+static unsigned long next_bit;  /* protected by iommu_bitmap_lock */
+static bool need_flush;		/* global flush state. set for each gart wrap */
+
+static unsigned long alloc_iommu(struct device *dev, int size,
+				 unsigned long align_mask)
+{
+	unsigned long offset, flags;
+	unsigned long boundary_size;
+	unsigned long base_index;
+
+	base_index = ALIGN(iommu_bus_base & dma_get_seg_boundary(dev),
+			   PAGE_SIZE) >> PAGE_SHIFT;
+	boundary_size = dma_get_seg_boundary_nr_pages(dev, PAGE_SHIFT);
+
+	spin_lock_irqsave(&iommu_bitmap_lock, flags);
+	offset = iommu_area_alloc(iommu_gart_bitmap, iommu_pages, next_bit,
+				  size, base_index, boundary_size, align_mask);
+	if (offset == -1) {
+		need_flush = true;
+		offset = iommu_area_alloc(iommu_gart_bitmap, iommu_pages, 0,
+					  size, base_index, boundary_size,
+					  align_mask);
+	}
+	if (offset != -1) {
+		next_bit = offset+size;
+		if (next_bit >= iommu_pages) {
+			next_bit = 0;
+			need_flush = true;
+		}
+	}
+	if (iommu_fullflush)
+		need_flush = true;
+	spin_unlock_irqrestore(&iommu_bitmap_lock, flags);
+
+	return offset;
+}
+
+static void free_iommu(unsigned long offset, int size)
+{
+	unsigned long flags;
+
+	spin_lock_irqsave(&iommu_bitmap_lock, flags);
+	bitmap_clear(iommu_gart_bitmap, offset, size);
+	if (offset >= next_bit)
+		next_bit = offset + size;
+	spin_unlock_irqrestore(&iommu_bitmap_lock, flags);
+}
+
+/*
+ * Use global flush state to avoid races with multiple flushers.
+ */
+static void flush_gart(void)
+{
+	unsigned long flags;
+
+	spin_lock_irqsave(&iommu_bitmap_lock, flags);
+	if (need_flush) {
+		amd_flush_garts();
+		need_flush = false;
+	}
+	spin_unlock_irqrestore(&iommu_bitmap_lock, flags);
+}
+
+#ifdef CONFIG_IOMMU_LEAK
+/* Debugging aid for drivers that don't free their IOMMU tables */
+static void dump_leak(void)
+{
+	static int dump;
+
+	if (dump)
+		return;
+	dump = 1;
+
+	show_stack(NULL, NULL, KERN_ERR);
+	debug_dma_dump_mappings(NULL);
+}
+#endif
+
+static void iommu_full(struct device *dev, size_t size, int dir)
+{
+	/*
+	 * Ran out of IOMMU space for this operation. This is very bad.
+	 * Unfortunately the drivers cannot handle this operation properly.
+	 * Return some non mapped prereserved space in the aperture and
+	 * let the Northbridge deal with it. This will result in garbage
+	 * in the IO operation. When the size exceeds the prereserved space
+	 * memory corruption will occur or random memory will be DMAed
+	 * out. Hopefully no network devices use single mappings that big.
+	 */
+
+	dev_err(dev, "PCI-DMA: Out of IOMMU space for %lu bytes\n", size);
+#ifdef CONFIG_IOMMU_LEAK
+	dump_leak();
+#endif
+}
+
+static inline int
+need_iommu(struct device *dev, unsigned long addr, size_t size)
+{
+	return force_iommu || !dma_capable(dev, addr, size, true);
+}
+
+static inline int
+nonforced_iommu(struct device *dev, unsigned long addr, size_t size)
+{
+	return !dma_capable(dev, addr, size, true);
+}
+
+/* Map a single continuous physical area into the IOMMU.
+ * Caller needs to check if the iommu is needed and flush.
+ */
+static dma_addr_t dma_map_area(struct device *dev, dma_addr_t phys_mem,
+				size_t size, int dir, unsigned long align_mask)
+{
+	unsigned long npages = iommu_num_pages(phys_mem, size, PAGE_SIZE);
+	unsigned long iommu_page;
+	int i;
+
+	if (unlikely(phys_mem + size > GART_MAX_PHYS_ADDR))
+		return DMA_MAPPING_ERROR;
+
+	iommu_page = alloc_iommu(dev, npages, align_mask);
+	if (iommu_page == -1) {
+		if (!nonforced_iommu(dev, phys_mem, size))
+			return phys_mem;
+		if (panic_on_overflow)
+			panic("dma_map_area overflow %lu bytes\n", size);
+		iommu_full(dev, size, dir);
+		return DMA_MAPPING_ERROR;
+	}
+
+	for (i = 0; i < npages; i++) {
+		iommu_gatt_base[iommu_page + i] = GPTE_ENCODE(phys_mem);
+		phys_mem += PAGE_SIZE;
+	}
+	return iommu_bus_base + iommu_page*PAGE_SIZE + (phys_mem & ~PAGE_MASK);
+}
+
+/* Map a single area into the IOMMU */
+static dma_addr_t gart_map_page(struct device *dev, struct page *page,
+				unsigned long offset, size_t size,
+				enum dma_data_direction dir,
+				unsigned long attrs)
+{
+	unsigned long bus;
+	phys_addr_t paddr = page_to_phys(page) + offset;
+
+	if (!need_iommu(dev, paddr, size))
+		return paddr;
+
+	bus = dma_map_area(dev, paddr, size, dir, 0);
+	flush_gart();
+
+	return bus;
+}
+
+/*
+ * Free a DMA mapping.
+ */
+static void gart_unmap_page(struct device *dev, dma_addr_t dma_addr,
+			    size_t size, enum dma_data_direction dir,
+			    unsigned long attrs)
+{
+	unsigned long iommu_page;
+	int npages;
+	int i;
+
+	if (WARN_ON_ONCE(dma_addr == DMA_MAPPING_ERROR))
+		return;
+
+	/*
+	 * This driver will not always use a GART mapping, but might have
+	 * created a direct mapping instead.  If that is the case there is
+	 * nothing to unmap here.
+	 */
+	if (dma_addr < iommu_bus_base ||
+	    dma_addr >= iommu_bus_base + iommu_size)
+		return;
+
+	iommu_page = (dma_addr - iommu_bus_base)>>PAGE_SHIFT;
+	npages = iommu_num_pages(dma_addr, size, PAGE_SIZE);
+	for (i = 0; i < npages; i++) {
+		iommu_gatt_base[iommu_page + i] = gart_unmapped_entry;
+	}
+	free_iommu(iommu_page, npages);
+}
+
+/*
+ * Wrapper for pci_unmap_single working with scatterlists.
+ */
+static void gart_unmap_sg(struct device *dev, struct scatterlist *sg, int nents,
+			  enum dma_data_direction dir, unsigned long attrs)
+{
+	struct scatterlist *s;
+	int i;
+
+	for_each_sg(sg, s, nents, i) {
+		if (!s->dma_length || !s->length)
+			break;
+		gart_unmap_page(dev, s->dma_address, s->dma_length, dir, 0);
+	}
+}
+
+/* Fallback for dma_map_sg in case of overflow */
+static int dma_map_sg_nonforce(struct device *dev, struct scatterlist *sg,
+			       int nents, int dir)
+{
+	struct scatterlist *s;
+	int i;
+
+#ifdef CONFIG_IOMMU_DEBUG
+	pr_debug("dma_map_sg overflow\n");
+#endif
+
+	for_each_sg(sg, s, nents, i) {
+		unsigned long addr = sg_phys(s);
+
+		if (nonforced_iommu(dev, addr, s->length)) {
+			addr = dma_map_area(dev, addr, s->length, dir, 0);
+			if (addr == DMA_MAPPING_ERROR) {
+				if (i > 0)
+					gart_unmap_sg(dev, sg, i, dir, 0);
+				nents = 0;
+				sg[0].dma_length = 0;
+				break;
+			}
+		}
+		s->dma_address = addr;
+		s->dma_length = s->length;
+	}
+	flush_gart();
+
+	return nents;
+}
+
+/* Map multiple scatterlist entries continuous into the first. */
+static int __dma_map_cont(struct device *dev, struct scatterlist *start,
+			  int nelems, struct scatterlist *sout,
+			  unsigned long pages)
+{
+	unsigned long iommu_start = alloc_iommu(dev, pages, 0);
+	unsigned long iommu_page = iommu_start;
+	struct scatterlist *s;
+	int i;
+
+	if (iommu_start == -1)
+		return -ENOMEM;
+
+	for_each_sg(start, s, nelems, i) {
+		unsigned long pages, addr;
+		unsigned long phys_addr = s->dma_address;
+
+		BUG_ON(s != start && s->offset);
+		if (s == start) {
+			sout->dma_address = iommu_bus_base;
+			sout->dma_address += iommu_page*PAGE_SIZE + s->offset;
+			sout->dma_length = s->length;
+		} else {
+			sout->dma_length += s->length;
+		}
+
+		addr = phys_addr;
+		pages = iommu_num_pages(s->offset, s->length, PAGE_SIZE);
+		while (pages--) {
+			iommu_gatt_base[iommu_page] = GPTE_ENCODE(addr);
+			addr += PAGE_SIZE;
+			iommu_page++;
+		}
+	}
+	BUG_ON(iommu_page - iommu_start != pages);
+
+	return 0;
+}
+
+static inline int
+dma_map_cont(struct device *dev, struct scatterlist *start, int nelems,
+	     struct scatterlist *sout, unsigned long pages, int need)
+{
+	if (!need) {
+		BUG_ON(nelems != 1);
+		sout->dma_address = start->dma_address;
+		sout->dma_length = start->length;
+		return 0;
+	}
+	return __dma_map_cont(dev, start, nelems, sout, pages);
+}
+
+/*
+ * DMA map all entries in a scatterlist.
+ * Merge chunks that have page aligned sizes into a continuous mapping.
+ */
+static int gart_map_sg(struct device *dev, struct scatterlist *sg, int nents,
+		       enum dma_data_direction dir, unsigned long attrs)
+{
+	struct scatterlist *s, *ps, *start_sg, *sgmap;
+	int need = 0, nextneed, i, out, start, ret;
+	unsigned long pages = 0;
+	unsigned int seg_size;
+	unsigned int max_seg_size;
+
+	if (nents == 0)
+		return -EINVAL;
+
+	out		= 0;
+	start		= 0;
+	start_sg	= sg;
+	sgmap		= sg;
+	seg_size	= 0;
+	max_seg_size	= dma_get_max_seg_size(dev);
+	ps		= NULL; /* shut up gcc */
+
+	for_each_sg(sg, s, nents, i) {
+		dma_addr_t addr = sg_phys(s);
+
+		s->dma_address = addr;
+		BUG_ON(s->length == 0);
+
+		nextneed = need_iommu(dev, addr, s->length);
+
+		/* Handle the previous not yet processed entries */
+		if (i > start) {
+			/*
+			 * Can only merge when the last chunk ends on a
+			 * page boundary and the new one doesn't have an
+			 * offset.
+			 */
+			if (!iommu_merge || !nextneed || !need || s->offset ||
+			    (s->length + seg_size > max_seg_size) ||
+			    (ps->offset + ps->length) % PAGE_SIZE) {
+				ret = dma_map_cont(dev, start_sg, i - start,
+						   sgmap, pages, need);
+				if (ret < 0)
+					goto error;
+				out++;
+
+				seg_size	= 0;
+				sgmap		= sg_next(sgmap);
+				pages		= 0;
+				start		= i;
+				start_sg	= s;
+			}
+		}
+
+		seg_size += s->length;
+		need = nextneed;
+		pages += iommu_num_pages(s->offset, s->length, PAGE_SIZE);
+		ps = s;
+	}
+	ret = dma_map_cont(dev, start_sg, i - start, sgmap, pages, need);
+	if (ret < 0)
+		goto error;
+	out++;
+	flush_gart();
+	if (out < nents) {
+		sgmap = sg_next(sgmap);
+		sgmap->dma_length = 0;
+	}
+	return out;
+
+error:
+	flush_gart();
+	gart_unmap_sg(dev, sg, out, dir, 0);
+
+	/* When it was forced or merged try again in a dumb way */
+	if (force_iommu || iommu_merge) {
+		out = dma_map_sg_nonforce(dev, sg, nents, dir);
+		if (out > 0)
+			return out;
+	}
+	if (panic_on_overflow)
+		panic("dma_map_sg: overflow on %lu pages\n", pages);
+
+	iommu_full(dev, pages << PAGE_SHIFT, dir);
+	return ret;
+}
+
+/* allocate and map a coherent mapping */
+static void *
+gart_alloc_coherent(struct device *dev, size_t size, dma_addr_t *dma_addr,
+		    gfp_t flag, unsigned long attrs)
+{
+	void *vaddr;
+
+	vaddr = dma_direct_alloc(dev, size, dma_addr, flag, attrs);
+	if (!vaddr ||
+	    !force_iommu || dev->coherent_dma_mask <= DMA_BIT_MASK(24))
+		return vaddr;
+
+	*dma_addr = dma_map_area(dev, virt_to_phys(vaddr), size,
+			DMA_BIDIRECTIONAL, (1UL << get_order(size)) - 1);
+	flush_gart();
+	if (unlikely(*dma_addr == DMA_MAPPING_ERROR))
+		goto out_free;
+	return vaddr;
+out_free:
+	dma_direct_free(dev, size, vaddr, *dma_addr, attrs);
+	return NULL;
+}
+
+/* free a coherent mapping */
+static void
+gart_free_coherent(struct device *dev, size_t size, void *vaddr,
+		   dma_addr_t dma_addr, unsigned long attrs)
+{
+	gart_unmap_page(dev, dma_addr, size, DMA_BIDIRECTIONAL, 0);
+	dma_direct_free(dev, size, vaddr, dma_addr, attrs);
+}
+
+static int no_agp;
+
+static __init unsigned long check_iommu_size(unsigned long aper, u64 aper_size)
+{
+	unsigned long a;
+
+	if (!iommu_size) {
+		iommu_size = aper_size;
+		if (!no_agp)
+			iommu_size /= 2;
+	}
+
+	a = aper + iommu_size;
+	iommu_size -= round_up(a, PMD_PAGE_SIZE) - a;
+
+	if (iommu_size < 64*1024*1024) {
+		pr_warn("PCI-DMA: Warning: Small IOMMU %luMB."
+			" Consider increasing the AGP aperture in BIOS\n",
+			iommu_size >> 20);
+	}
+
+	return iommu_size;
+}
+
+static __init unsigned read_aperture(struct pci_dev *dev, u32 *size)
+{
+	unsigned aper_size = 0, aper_base_32, aper_order;
+	u64 aper_base;
+
+	pci_read_config_dword(dev, AMD64_GARTAPERTUREBASE, &aper_base_32);
+	pci_read_config_dword(dev, AMD64_GARTAPERTURECTL, &aper_order);
+	aper_order = (aper_order >> 1) & 7;
+
+	aper_base = aper_base_32 & 0x7fff;
+	aper_base <<= 25;
+
+	aper_size = (32 * 1024 * 1024) << aper_order;
+	if (aper_base + aper_size > 0x100000000UL || !aper_size)
+		aper_base = 0;
+
+	*size = aper_size;
+	return aper_base;
+}
+
+static void enable_gart_translations(void)
+{
+	int i;
+
+	if (!amd_nb_has_feature(AMD_NB_GART))
+		return;
+
+	for (i = 0; i < amd_nb_num(); i++) {
+		struct pci_dev *dev = node_to_amd_nb(i)->misc;
+
+		enable_gart_translation(dev, __pa(agp_gatt_table));
+	}
+
+	/* Flush the GART-TLB to remove stale entries */
+	amd_flush_garts();
+}
+
+/*
+ * If fix_up_north_bridges is set, the north bridges have to be fixed up on
+ * resume in the same way as they are handled in gart_iommu_hole_init().
+ */
+static bool fix_up_north_bridges;
+static u32 aperture_order;
+static u32 aperture_alloc;
+
+void set_up_gart_resume(u32 aper_order, u32 aper_alloc)
+{
+	fix_up_north_bridges = true;
+	aperture_order = aper_order;
+	aperture_alloc = aper_alloc;
+}
+
+static void gart_fixup_northbridges(void)
+{
+	int i;
+
+	if (!fix_up_north_bridges)
+		return;
+
+	if (!amd_nb_has_feature(AMD_NB_GART))
+		return;
+
+	pr_info("PCI-DMA: Restoring GART aperture settings\n");
+
+	for (i = 0; i < amd_nb_num(); i++) {
+		struct pci_dev *dev = node_to_amd_nb(i)->misc;
+
+		/*
+		 * Don't enable translations just yet.  That is the next
+		 * step.  Restore the pre-suspend aperture settings.
+		 */
+		gart_set_size_and_enable(dev, aperture_order);
+		pci_write_config_dword(dev, AMD64_GARTAPERTUREBASE, aperture_alloc >> 25);
+	}
+}
+
+static void gart_resume(void)
+{
+	pr_info("PCI-DMA: Resuming GART IOMMU\n");
+
+	gart_fixup_northbridges();
+
+	enable_gart_translations();
+}
+
+static struct syscore_ops gart_syscore_ops = {
+	.resume		= gart_resume,
+
+};
+
+/*
+ * Private Northbridge GATT initialization in case we cannot use the
+ * AGP driver for some reason.
+ */
+static __init int init_amd_gatt(struct agp_kern_info *info)
+{
+	unsigned aper_size, gatt_size, new_aper_size;
+	unsigned aper_base, new_aper_base;
+	struct pci_dev *dev;
+	void *gatt;
+	int i;
+
+	pr_info("PCI-DMA: Disabling AGP.\n");
+
+	aper_size = aper_base = info->aper_size = 0;
+	dev = NULL;
+	for (i = 0; i < amd_nb_num(); i++) {
+		dev = node_to_amd_nb(i)->misc;
+		new_aper_base = read_aperture(dev, &new_aper_size);
+		if (!new_aper_base)
+			goto nommu;
+
+		if (!aper_base) {
+			aper_size = new_aper_size;
+			aper_base = new_aper_base;
+		}
+		if (aper_size != new_aper_size || aper_base != new_aper_base)
+			goto nommu;
+	}
+	if (!aper_base)
+		goto nommu;
+
+	info->aper_base = aper_base;
+	info->aper_size = aper_size >> 20;
+
+	gatt_size = (aper_size >> PAGE_SHIFT) * sizeof(u32);
+	gatt = (void *)__get_free_pages(GFP_KERNEL | __GFP_ZERO,
+					get_order(gatt_size));
+	if (!gatt)
+		panic("Cannot allocate GATT table");
+	if (set_memory_uc((unsigned long)gatt, gatt_size >> PAGE_SHIFT))
+		panic("Could not set GART PTEs to uncacheable pages");
+
+	agp_gatt_table = gatt;
+
+	register_syscore_ops(&gart_syscore_ops);
+
+	flush_gart();
+
+	pr_info("PCI-DMA: aperture base @ %x size %u KB\n",
+	       aper_base, aper_size>>10);
+
+	return 0;
+
+ nommu:
+	/* Should not happen anymore */
+	pr_warn("PCI-DMA: More than 4GB of RAM and no IOMMU - falling back to iommu=soft.\n");
+	return -1;
+}
+
+static const struct dma_map_ops gart_dma_ops = {
+	.map_sg				= gart_map_sg,
+	.unmap_sg			= gart_unmap_sg,
+	.map_page			= gart_map_page,
+	.unmap_page			= gart_unmap_page,
+	.alloc				= gart_alloc_coherent,
+	.free				= gart_free_coherent,
+	.mmap				= dma_common_mmap,
+	.get_sgtable			= dma_common_get_sgtable,
+	.dma_supported			= dma_direct_supported,
+	.get_required_mask		= dma_direct_get_required_mask,
+	.alloc_pages			= dma_direct_alloc_pages,
+	.free_pages			= dma_direct_free_pages,
+};
+
+static void gart_iommu_shutdown(void)
+{
+	struct pci_dev *dev;
+	int i;
+
+	/* don't shutdown it if there is AGP installed */
+	if (!no_agp)
+		return;
+
+	if (!amd_nb_has_feature(AMD_NB_GART))
+		return;
+
+	for (i = 0; i < amd_nb_num(); i++) {
+		u32 ctl;
+
+		dev = node_to_amd_nb(i)->misc;
+		pci_read_config_dword(dev, AMD64_GARTAPERTURECTL, &ctl);
+
+		ctl &= ~GARTEN;
+
+		pci_write_config_dword(dev, AMD64_GARTAPERTURECTL, ctl);
+	}
+}
+
+int __init gart_iommu_init(void)
+{
+	struct agp_kern_info info;
+	unsigned long iommu_start;
+	unsigned long aper_base, aper_size;
+	unsigned long start_pfn, end_pfn;
+	unsigned long scratch;
+
+	if (!amd_nb_has_feature(AMD_NB_GART))
+		return 0;
+
+#ifndef CONFIG_AGP_AMD64
+	no_agp = 1;
+#else
+	/* Makefile puts PCI initialization via subsys_initcall first. */
+	/* Add other AMD AGP bridge drivers here */
+	no_agp = no_agp ||
+		(agp_amd64_init() < 0) ||
+		(agp_copy_info(agp_bridge, &info) < 0);
+#endif
+
+	if (no_iommu ||
+	    (!force_iommu && max_pfn <= MAX_DMA32_PFN) ||
+	    !gart_iommu_aperture ||
+	    (no_agp && init_amd_gatt(&info) < 0)) {
+		if (max_pfn > MAX_DMA32_PFN) {
+			pr_warn("More than 4GB of memory but GART IOMMU not available.\n");
+			pr_warn("falling back to iommu=soft.\n");
+		}
+		return 0;
+	}
+
+	/* need to map that range */
+	aper_size	= info.aper_size << 20;
+	aper_base	= info.aper_base;
+	end_pfn		= (aper_base>>PAGE_SHIFT) + (aper_size>>PAGE_SHIFT);
+
+	start_pfn = PFN_DOWN(aper_base);
+	if (!pfn_range_is_mapped(start_pfn, end_pfn))
+		init_memory_mapping(start_pfn<<PAGE_SHIFT, end_pfn<<PAGE_SHIFT,
+				    PAGE_KERNEL);
+
+	pr_info("PCI-DMA: using GART IOMMU.\n");
+	iommu_size = check_iommu_size(info.aper_base, aper_size);
+	iommu_pages = iommu_size >> PAGE_SHIFT;
+
+	iommu_gart_bitmap = (void *) __get_free_pages(GFP_KERNEL | __GFP_ZERO,
+						      get_order(iommu_pages/8));
+	if (!iommu_gart_bitmap)
+		panic("Cannot allocate iommu bitmap\n");
+
+	pr_info("PCI-DMA: Reserving %luMB of IOMMU area in the AGP aperture\n",
+	       iommu_size >> 20);
+
+	agp_memory_reserved	= iommu_size;
+	iommu_start		= aper_size - iommu_size;
+	iommu_bus_base		= info.aper_base + iommu_start;
+	iommu_gatt_base		= agp_gatt_table + (iommu_start>>PAGE_SHIFT);
+
+	/*
+	 * Unmap the IOMMU part of the GART. The alias of the page is
+	 * always mapped with cache enabled and there is no full cache
+	 * coherency across the GART remapping. The unmapping avoids
+	 * automatic prefetches from the CPU allocating cache lines in
+	 * there. All CPU accesses are done via the direct mapping to
+	 * the backing memory. The GART address is only used by PCI
+	 * devices.
+	 */
+	set_memory_np((unsigned long)__va(iommu_bus_base),
+				iommu_size >> PAGE_SHIFT);
+	/*
+	 * Tricky. The GART table remaps the physical memory range,
+	 * so the CPU wont notice potential aliases and if the memory
+	 * is remapped to UC later on, we might surprise the PCI devices
+	 * with a stray writeout of a cacheline. So play it sure and
+	 * do an explicit, full-scale wbinvd() _after_ having marked all
+	 * the pages as Not-Present:
+	 */
+	wbinvd();
+
+	/*
+	 * Now all caches are flushed and we can safely enable
+	 * GART hardware.  Doing it early leaves the possibility
+	 * of stale cache entries that can lead to GART PTE
+	 * errors.
+	 */
+	enable_gart_translations();
+
+	/*
+	 * Try to workaround a bug (thanks to BenH):
+	 * Set unmapped entries to a scratch page instead of 0.
+	 * Any prefetches that hit unmapped entries won't get an bus abort
+	 * then. (P2P bridge may be prefetching on DMA reads).
+	 */
+	scratch = get_zeroed_page(GFP_KERNEL);
+	if (!scratch)
+		panic("Cannot allocate iommu scratch page");
+	gart_unmapped_entry = GPTE_ENCODE(__pa(scratch));
+
+	flush_gart();
+	dma_ops = &gart_dma_ops;
+	x86_platform.iommu_shutdown = gart_iommu_shutdown;
+	x86_swiotlb_enable = false;
+
+	return 0;
+}
+
+void __init gart_parse_options(char *p)
+{
+	int arg;
+
+	if (isdigit(*p) && get_option(&p, &arg))
+		iommu_size = arg;
+	if (!strncmp(p, "fullflush", 9))
+		iommu_fullflush = 1;
+	if (!strncmp(p, "nofullflush", 11))
+		iommu_fullflush = 0;
+	if (!strncmp(p, "noagp", 5))
+		no_agp = 1;
+	if (!strncmp(p, "noaperture", 10))
+		fix_aperture = 0;
+	/* duplicated from pci-dma.c */
+	if (!strncmp(p, "force", 5))
+		gart_iommu_aperture_allowed = 1;
+	if (!strncmp(p, "allowed", 7))
+		gart_iommu_aperture_allowed = 1;
+	if (!strncmp(p, "memaper", 7)) {
+		fallback_aper_force = 1;
+		p += 7;
+		if (*p == '=') {
+			++p;
+			if (get_option(&p, &arg))
+				fallback_aper_order = arg;
+		}
+	}
+}