Merge ../linux-2.6
[linux-2.6] / arch / arm / mm / mm-armv.c
1 /*
2  *  linux/arch/arm/mm/mm-armv.c
3  *
4  *  Copyright (C) 1998-2005 Russell King
5  *
6  * This program is free software; you can redistribute it and/or modify
7  * it under the terms of the GNU General Public License version 2 as
8  * published by the Free Software Foundation.
9  *
10  *  Page table sludge for ARM v3 and v4 processor architectures.
11  */
12 #include <linux/config.h>
13 #include <linux/module.h>
14 #include <linux/mm.h>
15 #include <linux/init.h>
16 #include <linux/bootmem.h>
17 #include <linux/highmem.h>
18 #include <linux/nodemask.h>
19
20 #include <asm/pgalloc.h>
21 #include <asm/page.h>
22 #include <asm/io.h>
23 #include <asm/setup.h>
24 #include <asm/tlbflush.h>
25
26 #include <asm/mach/map.h>
27
28 #define CPOLICY_UNCACHED        0
29 #define CPOLICY_BUFFERED        1
30 #define CPOLICY_WRITETHROUGH    2
31 #define CPOLICY_WRITEBACK       3
32 #define CPOLICY_WRITEALLOC      4
33
34 static unsigned int cachepolicy __initdata = CPOLICY_WRITEBACK;
35 static unsigned int ecc_mask __initdata = 0;
36 pgprot_t pgprot_kernel;
37
38 EXPORT_SYMBOL(pgprot_kernel);
39
40 pmd_t *top_pmd;
41
42 struct cachepolicy {
43         const char      policy[16];
44         unsigned int    cr_mask;
45         unsigned int    pmd;
46         unsigned int    pte;
47 };
48
49 static struct cachepolicy cache_policies[] __initdata = {
50         {
51                 .policy         = "uncached",
52                 .cr_mask        = CR_W|CR_C,
53                 .pmd            = PMD_SECT_UNCACHED,
54                 .pte            = 0,
55         }, {
56                 .policy         = "buffered",
57                 .cr_mask        = CR_C,
58                 .pmd            = PMD_SECT_BUFFERED,
59                 .pte            = PTE_BUFFERABLE,
60         }, {
61                 .policy         = "writethrough",
62                 .cr_mask        = 0,
63                 .pmd            = PMD_SECT_WT,
64                 .pte            = PTE_CACHEABLE,
65         }, {
66                 .policy         = "writeback",
67                 .cr_mask        = 0,
68                 .pmd            = PMD_SECT_WB,
69                 .pte            = PTE_BUFFERABLE|PTE_CACHEABLE,
70         }, {
71                 .policy         = "writealloc",
72                 .cr_mask        = 0,
73                 .pmd            = PMD_SECT_WBWA,
74                 .pte            = PTE_BUFFERABLE|PTE_CACHEABLE,
75         }
76 };
77
78 /*
79  * These are useful for identifing cache coherency
80  * problems by allowing the cache or the cache and
81  * writebuffer to be turned off.  (Note: the write
82  * buffer should not be on and the cache off).
83  */
84 static void __init early_cachepolicy(char **p)
85 {
86         int i;
87
88         for (i = 0; i < ARRAY_SIZE(cache_policies); i++) {
89                 int len = strlen(cache_policies[i].policy);
90
91                 if (memcmp(*p, cache_policies[i].policy, len) == 0) {
92                         cachepolicy = i;
93                         cr_alignment &= ~cache_policies[i].cr_mask;
94                         cr_no_alignment &= ~cache_policies[i].cr_mask;
95                         *p += len;
96                         break;
97                 }
98         }
99         if (i == ARRAY_SIZE(cache_policies))
100                 printk(KERN_ERR "ERROR: unknown or unsupported cache policy\n");
101         flush_cache_all();
102         set_cr(cr_alignment);
103 }
104
105 static void __init early_nocache(char **__unused)
106 {
107         char *p = "buffered";
108         printk(KERN_WARNING "nocache is deprecated; use cachepolicy=%s\n", p);
109         early_cachepolicy(&p);
110 }
111
112 static void __init early_nowrite(char **__unused)
113 {
114         char *p = "uncached";
115         printk(KERN_WARNING "nowb is deprecated; use cachepolicy=%s\n", p);
116         early_cachepolicy(&p);
117 }
118
119 static void __init early_ecc(char **p)
120 {
121         if (memcmp(*p, "on", 2) == 0) {
122                 ecc_mask = PMD_PROTECTION;
123                 *p += 2;
124         } else if (memcmp(*p, "off", 3) == 0) {
125                 ecc_mask = 0;
126                 *p += 3;
127         }
128 }
129
130 __early_param("nocache", early_nocache);
131 __early_param("nowb", early_nowrite);
132 __early_param("cachepolicy=", early_cachepolicy);
133 __early_param("ecc=", early_ecc);
134
135 static int __init noalign_setup(char *__unused)
136 {
137         cr_alignment &= ~CR_A;
138         cr_no_alignment &= ~CR_A;
139         set_cr(cr_alignment);
140         return 1;
141 }
142
143 __setup("noalign", noalign_setup);
144
145 #define FIRST_KERNEL_PGD_NR     (FIRST_USER_PGD_NR + USER_PTRS_PER_PGD)
146
147 static inline pmd_t *pmd_off(pgd_t *pgd, unsigned long virt)
148 {
149         return pmd_offset(pgd, virt);
150 }
151
152 static inline pmd_t *pmd_off_k(unsigned long virt)
153 {
154         return pmd_off(pgd_offset_k(virt), virt);
155 }
156
157 /*
158  * need to get a 16k page for level 1
159  */
160 pgd_t *get_pgd_slow(struct mm_struct *mm)
161 {
162         pgd_t *new_pgd, *init_pgd;
163         pmd_t *new_pmd, *init_pmd;
164         pte_t *new_pte, *init_pte;
165
166         new_pgd = (pgd_t *)__get_free_pages(GFP_KERNEL, 2);
167         if (!new_pgd)
168                 goto no_pgd;
169
170         memzero(new_pgd, FIRST_KERNEL_PGD_NR * sizeof(pgd_t));
171
172         /*
173          * Copy over the kernel and IO PGD entries
174          */
175         init_pgd = pgd_offset_k(0);
176         memcpy(new_pgd + FIRST_KERNEL_PGD_NR, init_pgd + FIRST_KERNEL_PGD_NR,
177                        (PTRS_PER_PGD - FIRST_KERNEL_PGD_NR) * sizeof(pgd_t));
178
179         clean_dcache_area(new_pgd, PTRS_PER_PGD * sizeof(pgd_t));
180
181         if (!vectors_high()) {
182                 /*
183                  * On ARM, first page must always be allocated since it
184                  * contains the machine vectors.
185                  */
186                 new_pmd = pmd_alloc(mm, new_pgd, 0);
187                 if (!new_pmd)
188                         goto no_pmd;
189
190                 new_pte = pte_alloc_map(mm, new_pmd, 0);
191                 if (!new_pte)
192                         goto no_pte;
193
194                 init_pmd = pmd_offset(init_pgd, 0);
195                 init_pte = pte_offset_map_nested(init_pmd, 0);
196                 set_pte(new_pte, *init_pte);
197                 pte_unmap_nested(init_pte);
198                 pte_unmap(new_pte);
199         }
200
201         return new_pgd;
202
203 no_pte:
204         pmd_free(new_pmd);
205 no_pmd:
206         free_pages((unsigned long)new_pgd, 2);
207 no_pgd:
208         return NULL;
209 }
210
211 void free_pgd_slow(pgd_t *pgd)
212 {
213         pmd_t *pmd;
214         struct page *pte;
215
216         if (!pgd)
217                 return;
218
219         /* pgd is always present and good */
220         pmd = pmd_off(pgd, 0);
221         if (pmd_none(*pmd))
222                 goto free;
223         if (pmd_bad(*pmd)) {
224                 pmd_ERROR(*pmd);
225                 pmd_clear(pmd);
226                 goto free;
227         }
228
229         pte = pmd_page(*pmd);
230         pmd_clear(pmd);
231         dec_page_state(nr_page_table_pages);
232         pte_lock_deinit(pte);
233         pte_free(pte);
234         pmd_free(pmd);
235 free:
236         free_pages((unsigned long) pgd, 2);
237 }
238
239 /*
240  * Create a SECTION PGD between VIRT and PHYS in domain
241  * DOMAIN with protection PROT.  This operates on half-
242  * pgdir entry increments.
243  */
244 static inline void
245 alloc_init_section(unsigned long virt, unsigned long phys, int prot)
246 {
247         pmd_t *pmdp = pmd_off_k(virt);
248
249         if (virt & (1 << 20))
250                 pmdp++;
251
252         *pmdp = __pmd(phys | prot);
253         flush_pmd_entry(pmdp);
254 }
255
256 /*
257  * Create a SUPER SECTION PGD between VIRT and PHYS with protection PROT
258  */
259 static inline void
260 alloc_init_supersection(unsigned long virt, unsigned long phys, int prot)
261 {
262         int i;
263
264         for (i = 0; i < 16; i += 1) {
265                 alloc_init_section(virt, phys, prot | PMD_SECT_SUPER);
266
267                 virt += (PGDIR_SIZE / 2);
268         }
269 }
270
271 /*
272  * Add a PAGE mapping between VIRT and PHYS in domain
273  * DOMAIN with protection PROT.  Note that due to the
274  * way we map the PTEs, we must allocate two PTE_SIZE'd
275  * blocks - one for the Linux pte table, and one for
276  * the hardware pte table.
277  */
278 static inline void
279 alloc_init_page(unsigned long virt, unsigned long phys, unsigned int prot_l1, pgprot_t prot)
280 {
281         pmd_t *pmdp = pmd_off_k(virt);
282         pte_t *ptep;
283
284         if (pmd_none(*pmdp)) {
285                 ptep = alloc_bootmem_low_pages(2 * PTRS_PER_PTE *
286                                                sizeof(pte_t));
287
288                 __pmd_populate(pmdp, __pa(ptep) | prot_l1);
289         }
290         ptep = pte_offset_kernel(pmdp, virt);
291
292         set_pte(ptep, pfn_pte(phys >> PAGE_SHIFT, prot));
293 }
294
295 struct mem_types {
296         unsigned int    prot_pte;
297         unsigned int    prot_l1;
298         unsigned int    prot_sect;
299         unsigned int    domain;
300 };
301
302 static struct mem_types mem_types[] __initdata = {
303         [MT_DEVICE] = {
304                 .prot_pte  = L_PTE_PRESENT | L_PTE_YOUNG | L_PTE_DIRTY |
305                                 L_PTE_WRITE,
306                 .prot_l1   = PMD_TYPE_TABLE,
307                 .prot_sect = PMD_TYPE_SECT | PMD_SECT_UNCACHED |
308                                 PMD_SECT_AP_WRITE,
309                 .domain    = DOMAIN_IO,
310         },
311         [MT_CACHECLEAN] = {
312                 .prot_sect = PMD_TYPE_SECT,
313                 .domain    = DOMAIN_KERNEL,
314         },
315         [MT_MINICLEAN] = {
316                 .prot_sect = PMD_TYPE_SECT | PMD_SECT_MINICACHE,
317                 .domain    = DOMAIN_KERNEL,
318         },
319         [MT_LOW_VECTORS] = {
320                 .prot_pte  = L_PTE_PRESENT | L_PTE_YOUNG | L_PTE_DIRTY |
321                                 L_PTE_EXEC,
322                 .prot_l1   = PMD_TYPE_TABLE,
323                 .domain    = DOMAIN_USER,
324         },
325         [MT_HIGH_VECTORS] = {
326                 .prot_pte  = L_PTE_PRESENT | L_PTE_YOUNG | L_PTE_DIRTY |
327                                 L_PTE_USER | L_PTE_EXEC,
328                 .prot_l1   = PMD_TYPE_TABLE,
329                 .domain    = DOMAIN_USER,
330         },
331         [MT_MEMORY] = {
332                 .prot_sect = PMD_TYPE_SECT | PMD_SECT_AP_WRITE,
333                 .domain    = DOMAIN_KERNEL,
334         },
335         [MT_ROM] = {
336                 .prot_sect = PMD_TYPE_SECT,
337                 .domain    = DOMAIN_KERNEL,
338         },
339         [MT_IXP2000_DEVICE] = { /* IXP2400 requires XCB=101 for on-chip I/O */
340                 .prot_pte  = L_PTE_PRESENT | L_PTE_YOUNG | L_PTE_DIRTY |
341                                 L_PTE_WRITE,
342                 .prot_l1   = PMD_TYPE_TABLE,
343                 .prot_sect = PMD_TYPE_SECT | PMD_SECT_UNCACHED |
344                                 PMD_SECT_AP_WRITE | PMD_SECT_BUFFERABLE |
345                                 PMD_SECT_TEX(1),
346                 .domain    = DOMAIN_IO,
347         }
348 };
349
350 /*
351  * Adjust the PMD section entries according to the CPU in use.
352  */
353 void __init build_mem_type_table(void)
354 {
355         struct cachepolicy *cp;
356         unsigned int cr = get_cr();
357         unsigned int user_pgprot, kern_pgprot;
358         int cpu_arch = cpu_architecture();
359         int i;
360
361 #if defined(CONFIG_CPU_DCACHE_DISABLE)
362         if (cachepolicy > CPOLICY_BUFFERED)
363                 cachepolicy = CPOLICY_BUFFERED;
364 #elif defined(CONFIG_CPU_DCACHE_WRITETHROUGH)
365         if (cachepolicy > CPOLICY_WRITETHROUGH)
366                 cachepolicy = CPOLICY_WRITETHROUGH;
367 #endif
368         if (cpu_arch < CPU_ARCH_ARMv5) {
369                 if (cachepolicy >= CPOLICY_WRITEALLOC)
370                         cachepolicy = CPOLICY_WRITEBACK;
371                 ecc_mask = 0;
372         }
373
374         if (cpu_arch <= CPU_ARCH_ARMv5TEJ) {
375                 for (i = 0; i < ARRAY_SIZE(mem_types); i++) {
376                         if (mem_types[i].prot_l1)
377                                 mem_types[i].prot_l1 |= PMD_BIT4;
378                         if (mem_types[i].prot_sect)
379                                 mem_types[i].prot_sect |= PMD_BIT4;
380                 }
381         }
382
383         cp = &cache_policies[cachepolicy];
384         kern_pgprot = user_pgprot = cp->pte;
385
386         /*
387          * ARMv6 and above have extended page tables.
388          */
389         if (cpu_arch >= CPU_ARCH_ARMv6 && (cr & CR_XP)) {
390                 /*
391                  * bit 4 becomes XN which we must clear for the
392                  * kernel memory mapping.
393                  */
394                 mem_types[MT_MEMORY].prot_sect &= ~PMD_BIT4;
395                 mem_types[MT_ROM].prot_sect &= ~PMD_BIT4;
396
397                 /*
398                  * Mark cache clean areas and XIP ROM read only
399                  * from SVC mode and no access from userspace.
400                  */
401                 mem_types[MT_ROM].prot_sect |= PMD_SECT_APX|PMD_SECT_AP_WRITE;
402                 mem_types[MT_MINICLEAN].prot_sect |= PMD_SECT_APX|PMD_SECT_AP_WRITE;
403                 mem_types[MT_CACHECLEAN].prot_sect |= PMD_SECT_APX|PMD_SECT_AP_WRITE;
404
405                 /*
406                  * Mark the device area as "shared device"
407                  */
408                 mem_types[MT_DEVICE].prot_pte |= L_PTE_BUFFERABLE;
409                 mem_types[MT_DEVICE].prot_sect |= PMD_SECT_BUFFERED;
410
411                 /*
412                  * User pages need to be mapped with the ASID
413                  * (iow, non-global)
414                  */
415                 user_pgprot |= L_PTE_ASID;
416
417 #ifdef CONFIG_SMP
418                 /*
419                  * Mark memory with the "shared" attribute for SMP systems
420                  */
421                 user_pgprot |= L_PTE_SHARED;
422                 kern_pgprot |= L_PTE_SHARED;
423                 mem_types[MT_MEMORY].prot_sect |= PMD_SECT_S;
424 #endif
425         }
426
427         for (i = 0; i < 16; i++) {
428                 unsigned long v = pgprot_val(protection_map[i]);
429                 v = (v & ~(L_PTE_BUFFERABLE|L_PTE_CACHEABLE)) | user_pgprot;
430                 protection_map[i] = __pgprot(v);
431         }
432
433         mem_types[MT_LOW_VECTORS].prot_pte |= kern_pgprot;
434         mem_types[MT_HIGH_VECTORS].prot_pte |= kern_pgprot;
435
436         if (cpu_arch >= CPU_ARCH_ARMv5) {
437 #ifndef CONFIG_SMP
438                 /*
439                  * Only use write-through for non-SMP systems
440                  */
441                 mem_types[MT_LOW_VECTORS].prot_pte &= ~L_PTE_BUFFERABLE;
442                 mem_types[MT_HIGH_VECTORS].prot_pte &= ~L_PTE_BUFFERABLE;
443 #endif
444         } else {
445                 mem_types[MT_MINICLEAN].prot_sect &= ~PMD_SECT_TEX(1);
446         }
447
448         pgprot_kernel = __pgprot(L_PTE_PRESENT | L_PTE_YOUNG |
449                                  L_PTE_DIRTY | L_PTE_WRITE |
450                                  L_PTE_EXEC | kern_pgprot);
451
452         mem_types[MT_LOW_VECTORS].prot_l1 |= ecc_mask;
453         mem_types[MT_HIGH_VECTORS].prot_l1 |= ecc_mask;
454         mem_types[MT_MEMORY].prot_sect |= ecc_mask | cp->pmd;
455         mem_types[MT_ROM].prot_sect |= cp->pmd;
456
457         switch (cp->pmd) {
458         case PMD_SECT_WT:
459                 mem_types[MT_CACHECLEAN].prot_sect |= PMD_SECT_WT;
460                 break;
461         case PMD_SECT_WB:
462         case PMD_SECT_WBWA:
463                 mem_types[MT_CACHECLEAN].prot_sect |= PMD_SECT_WB;
464                 break;
465         }
466         printk("Memory policy: ECC %sabled, Data cache %s\n",
467                 ecc_mask ? "en" : "dis", cp->policy);
468 }
469
470 #define vectors_base()  (vectors_high() ? 0xffff0000 : 0)
471
472 /*
473  * Create the page directory entries and any necessary
474  * page tables for the mapping specified by `md'.  We
475  * are able to cope here with varying sizes and address
476  * offsets, and we take full advantage of sections and
477  * supersections.
478  */
479 void __init create_mapping(struct map_desc *md)
480 {
481         unsigned long virt, length;
482         int prot_sect, prot_l1, domain;
483         pgprot_t prot_pte;
484         unsigned long off = (u32)__pfn_to_phys(md->pfn);
485
486         if (md->virtual != vectors_base() && md->virtual < TASK_SIZE) {
487                 printk(KERN_WARNING "BUG: not creating mapping for "
488                        "0x%08llx at 0x%08lx in user region\n",
489                        __pfn_to_phys((u64)md->pfn), md->virtual);
490                 return;
491         }
492
493         if ((md->type == MT_DEVICE || md->type == MT_ROM) &&
494             md->virtual >= PAGE_OFFSET && md->virtual < VMALLOC_END) {
495                 printk(KERN_WARNING "BUG: mapping for 0x%08llx at 0x%08lx "
496                        "overlaps vmalloc space\n",
497                        __pfn_to_phys((u64)md->pfn), md->virtual);
498         }
499
500         domain    = mem_types[md->type].domain;
501         prot_pte  = __pgprot(mem_types[md->type].prot_pte);
502         prot_l1   = mem_types[md->type].prot_l1 | PMD_DOMAIN(domain);
503         prot_sect = mem_types[md->type].prot_sect | PMD_DOMAIN(domain);
504
505         /*
506          * Catch 36-bit addresses
507          */
508         if(md->pfn >= 0x100000) {
509                 if(domain) {
510                         printk(KERN_ERR "MM: invalid domain in supersection "
511                                 "mapping for 0x%08llx at 0x%08lx\n",
512                                 __pfn_to_phys((u64)md->pfn), md->virtual);
513                         return;
514                 }
515                 if((md->virtual | md->length | __pfn_to_phys(md->pfn))
516                         & ~SUPERSECTION_MASK) {
517                         printk(KERN_ERR "MM: cannot create mapping for "
518                                 "0x%08llx at 0x%08lx invalid alignment\n",
519                                 __pfn_to_phys((u64)md->pfn), md->virtual);
520                         return;
521                 }
522
523                 /*
524                  * Shift bits [35:32] of address into bits [23:20] of PMD
525                  * (See ARMv6 spec).
526                  */
527                 off |= (((md->pfn >> (32 - PAGE_SHIFT)) & 0xF) << 20);
528         }
529
530         virt   = md->virtual;
531         off   -= virt;
532         length = md->length;
533
534         if (mem_types[md->type].prot_l1 == 0 &&
535             (virt & 0xfffff || (virt + off) & 0xfffff || (virt + length) & 0xfffff)) {
536                 printk(KERN_WARNING "BUG: map for 0x%08lx at 0x%08lx can not "
537                        "be mapped using pages, ignoring.\n",
538                        __pfn_to_phys(md->pfn), md->virtual);
539                 return;
540         }
541
542         while ((virt & 0xfffff || (virt + off) & 0xfffff) && length >= PAGE_SIZE) {
543                 alloc_init_page(virt, virt + off, prot_l1, prot_pte);
544
545                 virt   += PAGE_SIZE;
546                 length -= PAGE_SIZE;
547         }
548
549         /* N.B. ARMv6 supersections are only defined to work with domain 0.
550          *      Since domain assignments can in fact be arbitrary, the
551          *      'domain == 0' check below is required to insure that ARMv6
552          *      supersections are only allocated for domain 0 regardless
553          *      of the actual domain assignments in use.
554          */
555         if (cpu_architecture() >= CPU_ARCH_ARMv6 && domain == 0) {
556                 /*
557                  * Align to supersection boundary if !high pages.
558                  * High pages have already been checked for proper
559                  * alignment above and they will fail the SUPSERSECTION_MASK
560                  * check because of the way the address is encoded into
561                  * offset.
562                  */
563                 if (md->pfn <= 0x100000) {
564                         while ((virt & ~SUPERSECTION_MASK ||
565                                 (virt + off) & ~SUPERSECTION_MASK) &&
566                                 length >= (PGDIR_SIZE / 2)) {
567                                 alloc_init_section(virt, virt + off, prot_sect);
568
569                                 virt   += (PGDIR_SIZE / 2);
570                                 length -= (PGDIR_SIZE / 2);
571                         }
572                 }
573
574                 while (length >= SUPERSECTION_SIZE) {
575                         alloc_init_supersection(virt, virt + off, prot_sect);
576
577                         virt   += SUPERSECTION_SIZE;
578                         length -= SUPERSECTION_SIZE;
579                 }
580         }
581
582         /*
583          * A section mapping covers half a "pgdir" entry.
584          */
585         while (length >= (PGDIR_SIZE / 2)) {
586                 alloc_init_section(virt, virt + off, prot_sect);
587
588                 virt   += (PGDIR_SIZE / 2);
589                 length -= (PGDIR_SIZE / 2);
590         }
591
592         while (length >= PAGE_SIZE) {
593                 alloc_init_page(virt, virt + off, prot_l1, prot_pte);
594
595                 virt   += PAGE_SIZE;
596                 length -= PAGE_SIZE;
597         }
598 }
599
600 /*
601  * In order to soft-boot, we need to insert a 1:1 mapping in place of
602  * the user-mode pages.  This will then ensure that we have predictable
603  * results when turning the mmu off
604  */
605 void setup_mm_for_reboot(char mode)
606 {
607         unsigned long base_pmdval;
608         pgd_t *pgd;
609         int i;
610
611         if (current->mm && current->mm->pgd)
612                 pgd = current->mm->pgd;
613         else
614                 pgd = init_mm.pgd;
615
616         base_pmdval = PMD_SECT_AP_WRITE | PMD_SECT_AP_READ | PMD_TYPE_SECT;
617         if (cpu_architecture() <= CPU_ARCH_ARMv5TEJ)
618                 base_pmdval |= PMD_BIT4;
619
620         for (i = 0; i < FIRST_USER_PGD_NR + USER_PTRS_PER_PGD; i++, pgd++) {
621                 unsigned long pmdval = (i << PGDIR_SHIFT) | base_pmdval;
622                 pmd_t *pmd;
623
624                 pmd = pmd_off(pgd, i << PGDIR_SHIFT);
625                 pmd[0] = __pmd(pmdval);
626                 pmd[1] = __pmd(pmdval + (1 << (PGDIR_SHIFT - 1)));
627                 flush_pmd_entry(pmd);
628         }
629 }
630
631 /*
632  * Create the architecture specific mappings
633  */
634 void __init iotable_init(struct map_desc *io_desc, int nr)
635 {
636         int i;
637
638         for (i = 0; i < nr; i++)
639                 create_mapping(io_desc + i);
640 }