2 * Dynamic DMA mapping support for AMD Hammer.
4 * Use the integrated AGP GART in the Hammer northbridge as an IOMMU for PCI.
5 * This allows to use PCI devices that only support 32bit addresses on systems
8 * See Documentation/DMA-mapping.txt for the interface specification.
10 * Copyright 2002 Andi Kleen, SuSE Labs.
11 * Subject to the GNU General Public License v2 only.
14 #include <linux/types.h>
15 #include <linux/ctype.h>
16 #include <linux/agp_backend.h>
17 #include <linux/init.h>
19 #include <linux/string.h>
20 #include <linux/spinlock.h>
21 #include <linux/pci.h>
22 #include <linux/module.h>
23 #include <linux/topology.h>
24 #include <linux/interrupt.h>
25 #include <linux/bitops.h>
26 #include <linux/kdebug.h>
27 #include <linux/scatterlist.h>
28 #include <linux/iommu-helper.h>
29 #include <linux/sysdev.h>
30 #include <asm/atomic.h>
33 #include <asm/pgtable.h>
34 #include <asm/proto.h>
35 #include <asm/iommu.h>
37 #include <asm/cacheflush.h>
38 #include <asm/swiotlb.h>
42 static unsigned long iommu_bus_base; /* GART remapping area (physical) */
43 static unsigned long iommu_size; /* size of remapping area bytes */
44 static unsigned long iommu_pages; /* .. and in pages */
46 static u32 *iommu_gatt_base; /* Remapping table */
49 * If this is disabled the IOMMU will use an optimized flushing strategy
50 * of only flushing when an mapping is reused. With it true the GART is
51 * flushed for every mapping. Problem is that doing the lazy flush seems
52 * to trigger bugs with some popular PCI cards, in particular 3ware (but
53 * has been also also seen with Qlogic at least).
55 int iommu_fullflush = 1;
57 /* Allocation bitmap for the remapping area: */
58 static DEFINE_SPINLOCK(iommu_bitmap_lock);
59 /* Guarded by iommu_bitmap_lock: */
60 static unsigned long *iommu_gart_bitmap;
62 static u32 gart_unmapped_entry;
65 #define GPTE_COHERENT 2
66 #define GPTE_ENCODE(x) \
67 (((x) & 0xfffff000) | (((x) >> 32) << 4) | GPTE_VALID | GPTE_COHERENT)
68 #define GPTE_DECODE(x) (((x) & 0xfffff000) | (((u64)(x) & 0xff0) << 28))
70 #define EMERGENCY_PAGES 32 /* = 128KB */
73 #define AGPEXTERN extern
78 /* backdoor interface to AGP driver */
79 AGPEXTERN int agp_memory_reserved;
80 AGPEXTERN __u32 *agp_gatt_table;
82 static unsigned long next_bit; /* protected by iommu_bitmap_lock */
83 static int need_flush; /* global flush state. set for each gart wrap */
85 static unsigned long alloc_iommu(struct device *dev, int size,
86 unsigned long align_mask)
88 unsigned long offset, flags;
89 unsigned long boundary_size;
90 unsigned long base_index;
92 base_index = ALIGN(iommu_bus_base & dma_get_seg_boundary(dev),
93 PAGE_SIZE) >> PAGE_SHIFT;
94 boundary_size = ALIGN((unsigned long long)dma_get_seg_boundary(dev) + 1,
95 PAGE_SIZE) >> PAGE_SHIFT;
97 spin_lock_irqsave(&iommu_bitmap_lock, flags);
98 offset = iommu_area_alloc(iommu_gart_bitmap, iommu_pages, next_bit,
99 size, base_index, boundary_size, align_mask);
102 offset = iommu_area_alloc(iommu_gart_bitmap, iommu_pages, 0,
103 size, base_index, boundary_size,
107 next_bit = offset+size;
108 if (next_bit >= iommu_pages) {
115 spin_unlock_irqrestore(&iommu_bitmap_lock, flags);
120 static void free_iommu(unsigned long offset, int size)
124 spin_lock_irqsave(&iommu_bitmap_lock, flags);
125 iommu_area_free(iommu_gart_bitmap, offset, size);
126 spin_unlock_irqrestore(&iommu_bitmap_lock, flags);
130 * Use global flush state to avoid races with multiple flushers.
132 static void flush_gart(void)
136 spin_lock_irqsave(&iommu_bitmap_lock, flags);
141 spin_unlock_irqrestore(&iommu_bitmap_lock, flags);
144 #ifdef CONFIG_IOMMU_LEAK
146 #define SET_LEAK(x) \
148 if (iommu_leak_tab) \
149 iommu_leak_tab[x] = __builtin_return_address(0);\
152 #define CLEAR_LEAK(x) \
154 if (iommu_leak_tab) \
155 iommu_leak_tab[x] = NULL; \
158 /* Debugging aid for drivers that don't free their IOMMU tables */
159 static void **iommu_leak_tab;
160 static int leak_trace;
161 static int iommu_leak_pages = 20;
163 static void dump_leak(void)
168 if (dump || !iommu_leak_tab)
171 show_stack(NULL, NULL);
173 /* Very crude. dump some from the end of the table too */
174 printk(KERN_DEBUG "Dumping %d pages from end of IOMMU:\n",
176 for (i = 0; i < iommu_leak_pages; i += 2) {
177 printk(KERN_DEBUG "%lu: ", iommu_pages-i);
178 printk_address((unsigned long) iommu_leak_tab[iommu_pages-i], 0);
179 printk(KERN_CONT "%c", (i+1)%2 == 0 ? '\n' : ' ');
181 printk(KERN_DEBUG "\n");
185 # define CLEAR_LEAK(x)
188 static void iommu_full(struct device *dev, size_t size, int dir)
191 * Ran out of IOMMU space for this operation. This is very bad.
192 * Unfortunately the drivers cannot handle this operation properly.
193 * Return some non mapped prereserved space in the aperture and
194 * let the Northbridge deal with it. This will result in garbage
195 * in the IO operation. When the size exceeds the prereserved space
196 * memory corruption will occur or random memory will be DMAed
197 * out. Hopefully no network devices use single mappings that big.
200 dev_err(dev, "PCI-DMA: Out of IOMMU space for %lu bytes\n", size);
202 if (size > PAGE_SIZE*EMERGENCY_PAGES) {
203 if (dir == PCI_DMA_FROMDEVICE || dir == PCI_DMA_BIDIRECTIONAL)
204 panic("PCI-DMA: Memory would be corrupted\n");
205 if (dir == PCI_DMA_TODEVICE || dir == PCI_DMA_BIDIRECTIONAL)
207 "PCI-DMA: Random memory would be DMAed\n");
209 #ifdef CONFIG_IOMMU_LEAK
215 need_iommu(struct device *dev, unsigned long addr, size_t size)
217 return force_iommu ||
218 !is_buffer_dma_capable(*dev->dma_mask, addr, size);
222 nonforced_iommu(struct device *dev, unsigned long addr, size_t size)
224 return !is_buffer_dma_capable(*dev->dma_mask, addr, size);
227 /* Map a single continuous physical area into the IOMMU.
228 * Caller needs to check if the iommu is needed and flush.
230 static dma_addr_t dma_map_area(struct device *dev, dma_addr_t phys_mem,
231 size_t size, int dir, unsigned long align_mask)
233 unsigned long npages = iommu_num_pages(phys_mem, size);
234 unsigned long iommu_page = alloc_iommu(dev, npages, align_mask);
237 if (iommu_page == -1) {
238 if (!nonforced_iommu(dev, phys_mem, size))
240 if (panic_on_overflow)
241 panic("dma_map_area overflow %lu bytes\n", size);
242 iommu_full(dev, size, dir);
243 return bad_dma_address;
246 for (i = 0; i < npages; i++) {
247 iommu_gatt_base[iommu_page + i] = GPTE_ENCODE(phys_mem);
248 SET_LEAK(iommu_page + i);
249 phys_mem += PAGE_SIZE;
251 return iommu_bus_base + iommu_page*PAGE_SIZE + (phys_mem & ~PAGE_MASK);
254 /* Map a single area into the IOMMU */
256 gart_map_single(struct device *dev, phys_addr_t paddr, size_t size, int dir)
261 dev = &x86_dma_fallback_dev;
263 if (!need_iommu(dev, paddr, size))
266 bus = dma_map_area(dev, paddr, size, dir, 0);
273 * Free a DMA mapping.
275 static void gart_unmap_single(struct device *dev, dma_addr_t dma_addr,
276 size_t size, int direction)
278 unsigned long iommu_page;
282 if (dma_addr < iommu_bus_base + EMERGENCY_PAGES*PAGE_SIZE ||
283 dma_addr >= iommu_bus_base + iommu_size)
286 iommu_page = (dma_addr - iommu_bus_base)>>PAGE_SHIFT;
287 npages = iommu_num_pages(dma_addr, size);
288 for (i = 0; i < npages; i++) {
289 iommu_gatt_base[iommu_page + i] = gart_unmapped_entry;
290 CLEAR_LEAK(iommu_page + i);
292 free_iommu(iommu_page, npages);
296 * Wrapper for pci_unmap_single working with scatterlists.
299 gart_unmap_sg(struct device *dev, struct scatterlist *sg, int nents, int dir)
301 struct scatterlist *s;
304 for_each_sg(sg, s, nents, i) {
305 if (!s->dma_length || !s->length)
307 gart_unmap_single(dev, s->dma_address, s->dma_length, dir);
311 /* Fallback for dma_map_sg in case of overflow */
312 static int dma_map_sg_nonforce(struct device *dev, struct scatterlist *sg,
315 struct scatterlist *s;
318 #ifdef CONFIG_IOMMU_DEBUG
319 printk(KERN_DEBUG "dma_map_sg overflow\n");
322 for_each_sg(sg, s, nents, i) {
323 unsigned long addr = sg_phys(s);
325 if (nonforced_iommu(dev, addr, s->length)) {
326 addr = dma_map_area(dev, addr, s->length, dir, 0);
327 if (addr == bad_dma_address) {
329 gart_unmap_sg(dev, sg, i, dir);
331 sg[0].dma_length = 0;
335 s->dma_address = addr;
336 s->dma_length = s->length;
343 /* Map multiple scatterlist entries continuous into the first. */
344 static int __dma_map_cont(struct device *dev, struct scatterlist *start,
345 int nelems, struct scatterlist *sout,
348 unsigned long iommu_start = alloc_iommu(dev, pages, 0);
349 unsigned long iommu_page = iommu_start;
350 struct scatterlist *s;
353 if (iommu_start == -1)
356 for_each_sg(start, s, nelems, i) {
357 unsigned long pages, addr;
358 unsigned long phys_addr = s->dma_address;
360 BUG_ON(s != start && s->offset);
362 sout->dma_address = iommu_bus_base;
363 sout->dma_address += iommu_page*PAGE_SIZE + s->offset;
364 sout->dma_length = s->length;
366 sout->dma_length += s->length;
370 pages = iommu_num_pages(s->offset, s->length);
372 iommu_gatt_base[iommu_page] = GPTE_ENCODE(addr);
373 SET_LEAK(iommu_page);
378 BUG_ON(iommu_page - iommu_start != pages);
384 dma_map_cont(struct device *dev, struct scatterlist *start, int nelems,
385 struct scatterlist *sout, unsigned long pages, int need)
389 sout->dma_address = start->dma_address;
390 sout->dma_length = start->length;
393 return __dma_map_cont(dev, start, nelems, sout, pages);
397 * DMA map all entries in a scatterlist.
398 * Merge chunks that have page aligned sizes into a continuous mapping.
401 gart_map_sg(struct device *dev, struct scatterlist *sg, int nents, int dir)
403 struct scatterlist *s, *ps, *start_sg, *sgmap;
404 int need = 0, nextneed, i, out, start;
405 unsigned long pages = 0;
406 unsigned int seg_size;
407 unsigned int max_seg_size;
413 dev = &x86_dma_fallback_dev;
417 start_sg = sgmap = sg;
419 max_seg_size = dma_get_max_seg_size(dev);
420 ps = NULL; /* shut up gcc */
421 for_each_sg(sg, s, nents, i) {
422 dma_addr_t addr = sg_phys(s);
424 s->dma_address = addr;
425 BUG_ON(s->length == 0);
427 nextneed = need_iommu(dev, addr, s->length);
429 /* Handle the previous not yet processed entries */
432 * Can only merge when the last chunk ends on a
433 * page boundary and the new one doesn't have an
436 if (!iommu_merge || !nextneed || !need || s->offset ||
437 (s->length + seg_size > max_seg_size) ||
438 (ps->offset + ps->length) % PAGE_SIZE) {
439 if (dma_map_cont(dev, start_sg, i - start,
440 sgmap, pages, need) < 0)
444 sgmap = sg_next(sgmap);
451 seg_size += s->length;
453 pages += iommu_num_pages(s->offset, s->length);
456 if (dma_map_cont(dev, start_sg, i - start, sgmap, pages, need) < 0)
461 sgmap = sg_next(sgmap);
462 sgmap->dma_length = 0;
468 gart_unmap_sg(dev, sg, out, dir);
470 /* When it was forced or merged try again in a dumb way */
471 if (force_iommu || iommu_merge) {
472 out = dma_map_sg_nonforce(dev, sg, nents, dir);
476 if (panic_on_overflow)
477 panic("dma_map_sg: overflow on %lu pages\n", pages);
479 iommu_full(dev, pages << PAGE_SHIFT, dir);
480 for_each_sg(sg, s, nents, i)
481 s->dma_address = bad_dma_address;
485 /* allocate and map a coherent mapping */
487 gart_alloc_coherent(struct device *dev, size_t size, dma_addr_t *dma_addr,
491 unsigned long align_mask;
493 vaddr = (void *)__get_free_pages(flag | __GFP_ZERO, get_order(size));
497 align_mask = (1UL << get_order(size)) - 1;
499 *dma_addr = dma_map_area(dev, __pa(vaddr), size, DMA_BIDIRECTIONAL,
503 if (*dma_addr != bad_dma_address)
506 free_pages((unsigned long)vaddr, get_order(size));
511 /* free a coherent mapping */
513 gart_free_coherent(struct device *dev, size_t size, void *vaddr,
516 gart_unmap_single(dev, dma_addr, size, DMA_BIDIRECTIONAL);
517 free_pages((unsigned long)vaddr, get_order(size));
522 static __init unsigned long check_iommu_size(unsigned long aper, u64 aper_size)
527 iommu_size = aper_size;
532 a = aper + iommu_size;
533 iommu_size -= round_up(a, PMD_PAGE_SIZE) - a;
535 if (iommu_size < 64*1024*1024) {
537 "PCI-DMA: Warning: Small IOMMU %luMB."
538 " Consider increasing the AGP aperture in BIOS\n",
545 static __init unsigned read_aperture(struct pci_dev *dev, u32 *size)
547 unsigned aper_size = 0, aper_base_32, aper_order;
550 pci_read_config_dword(dev, AMD64_GARTAPERTUREBASE, &aper_base_32);
551 pci_read_config_dword(dev, AMD64_GARTAPERTURECTL, &aper_order);
552 aper_order = (aper_order >> 1) & 7;
554 aper_base = aper_base_32 & 0x7fff;
557 aper_size = (32 * 1024 * 1024) << aper_order;
558 if (aper_base + aper_size > 0x100000000UL || !aper_size)
565 static void enable_gart_translations(void)
569 for (i = 0; i < num_k8_northbridges; i++) {
570 struct pci_dev *dev = k8_northbridges[i];
572 enable_gart_translation(dev, __pa(agp_gatt_table));
577 * If fix_up_north_bridges is set, the north bridges have to be fixed up on
578 * resume in the same way as they are handled in gart_iommu_hole_init().
580 static bool fix_up_north_bridges;
581 static u32 aperture_order;
582 static u32 aperture_alloc;
584 void set_up_gart_resume(u32 aper_order, u32 aper_alloc)
586 fix_up_north_bridges = true;
587 aperture_order = aper_order;
588 aperture_alloc = aper_alloc;
591 static int gart_resume(struct sys_device *dev)
593 printk(KERN_INFO "PCI-DMA: Resuming GART IOMMU\n");
595 if (fix_up_north_bridges) {
598 printk(KERN_INFO "PCI-DMA: Restoring GART aperture settings\n");
600 for (i = 0; i < num_k8_northbridges; i++) {
601 struct pci_dev *dev = k8_northbridges[i];
604 * Don't enable translations just yet. That is the next
605 * step. Restore the pre-suspend aperture settings.
607 pci_write_config_dword(dev, AMD64_GARTAPERTURECTL,
608 aperture_order << 1);
609 pci_write_config_dword(dev, AMD64_GARTAPERTUREBASE,
610 aperture_alloc >> 25);
614 enable_gart_translations();
619 static int gart_suspend(struct sys_device *dev, pm_message_t state)
624 static struct sysdev_class gart_sysdev_class = {
626 .suspend = gart_suspend,
627 .resume = gart_resume,
631 static struct sys_device device_gart = {
633 .cls = &gart_sysdev_class,
637 * Private Northbridge GATT initialization in case we cannot use the
638 * AGP driver for some reason.
640 static __init int init_k8_gatt(struct agp_kern_info *info)
642 unsigned aper_size, gatt_size, new_aper_size;
643 unsigned aper_base, new_aper_base;
647 unsigned long start_pfn, end_pfn;
649 printk(KERN_INFO "PCI-DMA: Disabling AGP.\n");
650 aper_size = aper_base = info->aper_size = 0;
652 for (i = 0; i < num_k8_northbridges; i++) {
653 dev = k8_northbridges[i];
654 new_aper_base = read_aperture(dev, &new_aper_size);
659 aper_size = new_aper_size;
660 aper_base = new_aper_base;
662 if (aper_size != new_aper_size || aper_base != new_aper_base)
667 info->aper_base = aper_base;
668 info->aper_size = aper_size >> 20;
670 gatt_size = (aper_size >> PAGE_SHIFT) * sizeof(u32);
671 gatt = (void *)__get_free_pages(GFP_KERNEL, get_order(gatt_size));
673 panic("Cannot allocate GATT table");
674 if (set_memory_uc((unsigned long)gatt, gatt_size >> PAGE_SHIFT))
675 panic("Could not set GART PTEs to uncacheable pages");
677 memset(gatt, 0, gatt_size);
678 agp_gatt_table = gatt;
680 enable_gart_translations();
682 error = sysdev_class_register(&gart_sysdev_class);
684 error = sysdev_register(&device_gart);
686 panic("Could not register gart_sysdev -- would corrupt data on next suspend");
690 printk(KERN_INFO "PCI-DMA: aperture base @ %x size %u KB\n",
691 aper_base, aper_size>>10);
693 /* need to map that range */
694 end_pfn = (aper_base>>PAGE_SHIFT) + (aper_size>>PAGE_SHIFT);
695 if (end_pfn > max_low_pfn_mapped) {
696 start_pfn = (aper_base>>PAGE_SHIFT);
697 init_memory_mapping(start_pfn<<PAGE_SHIFT, end_pfn<<PAGE_SHIFT);
702 /* Should not happen anymore */
703 printk(KERN_WARNING "PCI-DMA: More than 4GB of RAM and no IOMMU\n"
704 KERN_WARNING "falling back to iommu=soft.\n");
708 extern int agp_amd64_init(void);
710 static struct dma_mapping_ops gart_dma_ops = {
711 .map_single = gart_map_single,
712 .unmap_single = gart_unmap_single,
713 .sync_single_for_cpu = NULL,
714 .sync_single_for_device = NULL,
715 .sync_single_range_for_cpu = NULL,
716 .sync_single_range_for_device = NULL,
717 .sync_sg_for_cpu = NULL,
718 .sync_sg_for_device = NULL,
719 .map_sg = gart_map_sg,
720 .unmap_sg = gart_unmap_sg,
721 .alloc_coherent = gart_alloc_coherent,
722 .free_coherent = gart_free_coherent,
725 void gart_iommu_shutdown(void)
730 if (no_agp && (dma_ops != &gart_dma_ops))
733 for (i = 0; i < num_k8_northbridges; i++) {
736 dev = k8_northbridges[i];
737 pci_read_config_dword(dev, AMD64_GARTAPERTURECTL, &ctl);
741 pci_write_config_dword(dev, AMD64_GARTAPERTURECTL, ctl);
745 void __init gart_iommu_init(void)
747 struct agp_kern_info info;
748 unsigned long iommu_start;
749 unsigned long aper_size;
750 unsigned long scratch;
753 if (cache_k8_northbridges() < 0 || num_k8_northbridges == 0) {
754 printk(KERN_INFO "PCI-GART: No AMD northbridge found.\n");
758 #ifndef CONFIG_AGP_AMD64
761 /* Makefile puts PCI initialization via subsys_initcall first. */
762 /* Add other K8 AGP bridge drivers here */
764 (agp_amd64_init() < 0) ||
765 (agp_copy_info(agp_bridge, &info) < 0);
771 /* Did we detect a different HW IOMMU? */
772 if (iommu_detected && !gart_iommu_aperture)
776 (!force_iommu && max_pfn <= MAX_DMA32_PFN) ||
777 !gart_iommu_aperture ||
778 (no_agp && init_k8_gatt(&info) < 0)) {
779 if (max_pfn > MAX_DMA32_PFN) {
780 printk(KERN_WARNING "More than 4GB of memory "
781 "but GART IOMMU not available.\n"
782 KERN_WARNING "falling back to iommu=soft.\n");
787 printk(KERN_INFO "PCI-DMA: using GART IOMMU.\n");
788 aper_size = info.aper_size * 1024 * 1024;
789 iommu_size = check_iommu_size(info.aper_base, aper_size);
790 iommu_pages = iommu_size >> PAGE_SHIFT;
792 iommu_gart_bitmap = (void *) __get_free_pages(GFP_KERNEL,
793 get_order(iommu_pages/8));
794 if (!iommu_gart_bitmap)
795 panic("Cannot allocate iommu bitmap\n");
796 memset(iommu_gart_bitmap, 0, iommu_pages/8);
798 #ifdef CONFIG_IOMMU_LEAK
800 iommu_leak_tab = (void *)__get_free_pages(GFP_KERNEL,
801 get_order(iommu_pages*sizeof(void *)));
803 memset(iommu_leak_tab, 0, iommu_pages * 8);
806 "PCI-DMA: Cannot allocate leak trace area\n");
811 * Out of IOMMU space handling.
812 * Reserve some invalid pages at the beginning of the GART.
814 set_bit_string(iommu_gart_bitmap, 0, EMERGENCY_PAGES);
816 agp_memory_reserved = iommu_size;
818 "PCI-DMA: Reserving %luMB of IOMMU area in the AGP aperture\n",
821 iommu_start = aper_size - iommu_size;
822 iommu_bus_base = info.aper_base + iommu_start;
823 bad_dma_address = iommu_bus_base;
824 iommu_gatt_base = agp_gatt_table + (iommu_start>>PAGE_SHIFT);
827 * Unmap the IOMMU part of the GART. The alias of the page is
828 * always mapped with cache enabled and there is no full cache
829 * coherency across the GART remapping. The unmapping avoids
830 * automatic prefetches from the CPU allocating cache lines in
831 * there. All CPU accesses are done via the direct mapping to
832 * the backing memory. The GART address is only used by PCI
835 set_memory_np((unsigned long)__va(iommu_bus_base),
836 iommu_size >> PAGE_SHIFT);
838 * Tricky. The GART table remaps the physical memory range,
839 * so the CPU wont notice potential aliases and if the memory
840 * is remapped to UC later on, we might surprise the PCI devices
841 * with a stray writeout of a cacheline. So play it sure and
842 * do an explicit, full-scale wbinvd() _after_ having marked all
843 * the pages as Not-Present:
848 * Try to workaround a bug (thanks to BenH):
849 * Set unmapped entries to a scratch page instead of 0.
850 * Any prefetches that hit unmapped entries won't get an bus abort
851 * then. (P2P bridge may be prefetching on DMA reads).
853 scratch = get_zeroed_page(GFP_KERNEL);
855 panic("Cannot allocate iommu scratch page");
856 gart_unmapped_entry = GPTE_ENCODE(__pa(scratch));
857 for (i = EMERGENCY_PAGES; i < iommu_pages; i++)
858 iommu_gatt_base[i] = gart_unmapped_entry;
861 dma_ops = &gart_dma_ops;
864 void __init gart_parse_options(char *p)
868 #ifdef CONFIG_IOMMU_LEAK
869 if (!strncmp(p, "leak", 4)) {
873 if (isdigit(*p) && get_option(&p, &arg))
874 iommu_leak_pages = arg;
877 if (isdigit(*p) && get_option(&p, &arg))
879 if (!strncmp(p, "fullflush", 8))
881 if (!strncmp(p, "nofullflush", 11))
883 if (!strncmp(p, "noagp", 5))
885 if (!strncmp(p, "noaperture", 10))
887 /* duplicated from pci-dma.c */
888 if (!strncmp(p, "force", 5))
889 gart_iommu_aperture_allowed = 1;
890 if (!strncmp(p, "allowed", 7))
891 gart_iommu_aperture_allowed = 1;
892 if (!strncmp(p, "memaper", 7)) {
893 fallback_aper_force = 1;
897 if (get_option(&p, &arg))
898 fallback_aper_order = arg;