arch/arm/mm/highmem.c

   1 /*
   2  * arch/arm/mm/highmem.c -- ARM highmem support
   3  *
   4  * Author:      Nicolas Pitre
   5  * Created:     september 8, 2008
   6  * Copyright:   Marvell Semiconductors Inc.
   7  *
   8  * This program is free software; you can redistribute it and/or modify
   9  * it under the terms of the GNU General Public License version 2 as
  10  * published by the Free Software Foundation.
  11  */
  12
  13 #include <linux/module.h>
  14 #include <linux/highmem.h>
  15 #include <linux/interrupt.h>
  16 #include <asm/fixmap.h>
  17 #include <asm/cacheflush.h>
  18 #include <asm/tlbflush.h>
  19 #include "mm.h"
  20
  21 void *kmap(struct page *page)
  22 {
  23         might_sleep();
  24         if (!PageHighMem(page))
  25                 return page_address(page);
  26         return kmap_high(page);
  27 }
  28 EXPORT_SYMBOL(kmap);
  29
  30 void kunmap(struct page *page)
  31 {
  32         BUG_ON(in_interrupt());
  33         if (!PageHighMem(page))
  34                 return;
  35         kunmap_high(page);
  36 }
  37 EXPORT_SYMBOL(kunmap);
  38
  39 void *__kmap_atomic(struct page *page)
  40 {
  41         unsigned int idx;
  42         unsigned long vaddr;
  43         void *kmap;
  44         int type;
  45
  46         pagefault_disable();
  47         if (!PageHighMem(page))
  48                 return page_address(page);
  49
  50 #ifdef CONFIG_DEBUG_HIGHMEM
  51         /*
  52          * There is no cache coherency issue when non VIVT, so force the
  53          * dedicated kmap usage for better debugging purposes in that case.
  54          */
  55         if (!cache_is_vivt())
  56                 kmap = NULL;
  57         else
  58 #endif
  59                 kmap = kmap_high_get(page);
  60         if (kmap)
  61                 return kmap;
  62
  63         type = kmap_atomic_idx_push();
  64
  65         idx = type + KM_TYPE_NR * smp_processor_id();
  66         vaddr = __fix_to_virt(FIX_KMAP_BEGIN + idx);
  67 #ifdef CONFIG_DEBUG_HIGHMEM
  68         /*
  69          * With debugging enabled, kunmap_atomic forces that entry to 0.
  70          * Make sure it was indeed properly unmapped.
  71          */
  72         BUG_ON(!pte_none(*(TOP_PTE(vaddr))));
  73 #endif
  74         set_pte_ext(TOP_PTE(vaddr), mk_pte(page, kmap_prot), 0);
  75         /*
  76          * When debugging is off, kunmap_atomic leaves the previous mapping
  77          * in place, so this TLB flush ensures the TLB is updated with the
  78          * new mapping.
  79          */
  80         local_flush_tlb_kernel_page(vaddr);
  81
  82         return (void *)vaddr;
  83 }
  84 EXPORT_SYMBOL(__kmap_atomic);
  85
  86 void __kunmap_atomic(void *kvaddr)
  87 {
  88         unsigned long vaddr = (unsigned long) kvaddr & PAGE_MASK;
  89         int idx, type;
  90
  91         if (kvaddr >= (void *)FIXADDR_START) {
  92                 type = kmap_atomic_idx();
  93                 idx = type + KM_TYPE_NR * smp_processor_id();
  94
  95                 if (cache_is_vivt())
  96                         __cpuc_flush_dcache_area((void *)vaddr, PAGE_SIZE);
  97 #ifdef CONFIG_DEBUG_HIGHMEM
  98                 BUG_ON(vaddr != __fix_to_virt(FIX_KMAP_BEGIN + idx));
  99                 set_pte_ext(TOP_PTE(vaddr), __pte(0), 0);
 100                 local_flush_tlb_kernel_page(vaddr);
 101 #else
 102                 (void) idx;  /* to kill a warning */
 103 #endif
 104                 kmap_atomic_idx_pop();
 105         } else if (vaddr >= PKMAP_ADDR(0) && vaddr < PKMAP_ADDR(LAST_PKMAP)) {
 106                 /* this address was obtained through kmap_high_get() */
 107                 kunmap_high(pte_page(pkmap_page_table[PKMAP_NR(vaddr)]));
 108         }
 109         pagefault_enable();
 110 }
 111 EXPORT_SYMBOL(__kunmap_atomic);
 112
 113 void *kmap_atomic_pfn(unsigned long pfn)
 114 {
 115         unsigned long vaddr;
 116         int idx, type;
 117
 118         pagefault_disable();
 119
 120         type = kmap_atomic_idx_push();
 121         idx = type + KM_TYPE_NR * smp_processor_id();
 122         vaddr = __fix_to_virt(FIX_KMAP_BEGIN + idx);
 123 #ifdef CONFIG_DEBUG_HIGHMEM
 124         BUG_ON(!pte_none(*(TOP_PTE(vaddr))));
 125 #endif
 126         set_pte_ext(TOP_PTE(vaddr), pfn_pte(pfn, kmap_prot), 0);
 127         local_flush_tlb_kernel_page(vaddr);
 128
 129         return (void *)vaddr;
 130 }
 131
 132 struct page *kmap_atomic_to_page(const void *ptr)
 133 {
 134         unsigned long vaddr = (unsigned long)ptr;
 135         pte_t *pte;
 136
 137         if (vaddr < FIXADDR_START)
 138                 return virt_to_page(ptr);
 139
 140         pte = TOP_PTE(vaddr);
 141         return pte_page(*pte);
 142 }
 143
 144 #ifdef CONFIG_CPU_CACHE_VIPT
 145
 146 #include <linux/percpu.h>
 147
 148 /*
 149  * The VIVT cache of a highmem page is always flushed before the page
 150  * is unmapped. Hence unmapped highmem pages need no cache maintenance
 151  * in that case.
 152  *
 153  * However unmapped pages may still be cached with a VIPT cache, and
 154  * it is not possible to perform cache maintenance on them using physical
 155  * addresses unfortunately.  So we have no choice but to set up a temporary
 156  * virtual mapping for that purpose.
 157  *
 158  * Yet this VIPT cache maintenance may be triggered from DMA support
 159  * functions which are possibly called from interrupt context. As we don't
 160  * want to keep interrupt disabled all the time when such maintenance is
 161  * taking place, we therefore allow for some reentrancy by preserving and
 162  * restoring the previous fixmap entry before the interrupted context is
 163  * resumed.  If the reentrancy depth is 0 then there is no need to restore
 164  * the previous fixmap, and leaving the current one in place allow it to
 165  * be reused the next time without a TLB flush (common with DMA).
 166  */
 167
 168 static DEFINE_PER_CPU(int, kmap_high_l1_vipt_depth);
 169
 170 void *kmap_high_l1_vipt(struct page *page, pte_t *saved_pte)
 171 {
 172         unsigned int idx, cpu;
 173         int *depth;
 174         unsigned long vaddr, flags;
 175         pte_t pte, *ptep;
 176
 177         if (!in_interrupt())
 178                 preempt_disable();
 179
 180         cpu = smp_processor_id();
 181         depth = &per_cpu(kmap_high_l1_vipt_depth, cpu);
 182
 183         idx = KM_L1_CACHE + KM_TYPE_NR * cpu;
 184         vaddr = __fix_to_virt(FIX_KMAP_BEGIN + idx);
 185         ptep = TOP_PTE(vaddr);
 186         pte = mk_pte(page, kmap_prot);
 187
 188         raw_local_irq_save(flags);
 189         (*depth)++;
 190         if (pte_val(*ptep) == pte_val(pte)) {
 191                 *saved_pte = pte;
 192         } else {
 193                 *saved_pte = *ptep;
 194                 set_pte_ext(ptep, pte, 0);
 195                 local_flush_tlb_kernel_page(vaddr);
 196         }
 197         raw_local_irq_restore(flags);
 198
 199         return (void *)vaddr;
 200 }
 201
 202 void kunmap_high_l1_vipt(struct page *page, pte_t saved_pte)
 203 {
 204         unsigned int idx, cpu = smp_processor_id();
 205         int *depth = &per_cpu(kmap_high_l1_vipt_depth, cpu);
 206         unsigned long vaddr, flags;
 207         pte_t pte, *ptep;
 208
 209         idx = KM_L1_CACHE + KM_TYPE_NR * cpu;
 210         vaddr = __fix_to_virt(FIX_KMAP_BEGIN + idx);
 211         ptep = TOP_PTE(vaddr);
 212         pte = mk_pte(page, kmap_prot);
 213
 214         BUG_ON(pte_val(*ptep) != pte_val(pte));
 215         BUG_ON(*depth <= 0);
 216
 217         raw_local_irq_save(flags);
 218         (*depth)--;
 219         if (*depth != 0 && pte_val(pte) != pte_val(saved_pte)) {
 220                 set_pte_ext(ptep, saved_pte, 0);
 221                 local_flush_tlb_kernel_page(vaddr);
 222         }
 223         raw_local_irq_restore(flags);
 224
 225         if (!in_interrupt())
 226                 preempt_enable();
 227 }
 228
 229 #endif  /* CONFIG_CPU_CACHE_VIPT */