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_pop();
  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         } else if (vaddr >= PKMAP_ADDR(0) && vaddr < PKMAP_ADDR(LAST_PKMAP)) {
 105                 /* this address was obtained through kmap_high_get() */
 106                 kunmap_high(pte_page(pkmap_page_table[PKMAP_NR(vaddr)]));
 107         }
 108         pagefault_enable();
 109 }
 110 EXPORT_SYMBOL(__kunmap_atomic);
 111
 112 void *kmap_atomic_pfn(unsigned long pfn)
 113 {
 114         unsigned long vaddr;
 115         int idx, type;
 116
 117         pagefault_disable();
 118
 119         type = kmap_atomic_idx_push();
 120         idx = type + KM_TYPE_NR * smp_processor_id();
 121         vaddr = __fix_to_virt(FIX_KMAP_BEGIN + idx);
 122 #ifdef CONFIG_DEBUG_HIGHMEM
 123         BUG_ON(!pte_none(*(TOP_PTE(vaddr))));
 124 #endif
 125         set_pte_ext(TOP_PTE(vaddr), pfn_pte(pfn, kmap_prot), 0);
 126         local_flush_tlb_kernel_page(vaddr);
 127
 128         return (void *)vaddr;
 129 }
 130
 131 struct page *kmap_atomic_to_page(const void *ptr)
 132 {
 133         unsigned long vaddr = (unsigned long)ptr;
 134         pte_t *pte;
 135
 136         if (vaddr < FIXADDR_START)
 137                 return virt_to_page(ptr);
 138
 139         pte = TOP_PTE(vaddr);
 140         return pte_page(*pte);
 141 }
 142
 143 #ifdef CONFIG_CPU_CACHE_VIPT
 144
 145 #include <linux/percpu.h>
 146
 147 /*
 148  * The VIVT cache of a highmem page is always flushed before the page
 149  * is unmapped. Hence unmapped highmem pages need no cache maintenance
 150  * in that case.
 151  *
 152  * However unmapped pages may still be cached with a VIPT cache, and
 153  * it is not possible to perform cache maintenance on them using physical
 154  * addresses unfortunately.  So we have no choice but to set up a temporary
 155  * virtual mapping for that purpose.
 156  *
 157  * Yet this VIPT cache maintenance may be triggered from DMA support
 158  * functions which are possibly called from interrupt context. As we don't
 159  * want to keep interrupt disabled all the time when such maintenance is
 160  * taking place, we therefore allow for some reentrancy by preserving and
 161  * restoring the previous fixmap entry before the interrupted context is
 162  * resumed.  If the reentrancy depth is 0 then there is no need to restore
 163  * the previous fixmap, and leaving the current one in place allow it to
 164  * be reused the next time without a TLB flush (common with DMA).
 165  */
 166
 167 static DEFINE_PER_CPU(int, kmap_high_l1_vipt_depth);
 168
 169 void *kmap_high_l1_vipt(struct page *page, pte_t *saved_pte)
 170 {
 171         unsigned int idx, cpu;
 172         int *depth;
 173         unsigned long vaddr, flags;
 174         pte_t pte, *ptep;
 175
 176         if (!in_interrupt())
 177                 preempt_disable();
 178
 179         cpu = smp_processor_id();
 180         depth = &per_cpu(kmap_high_l1_vipt_depth, cpu);
 181
 182         idx = KM_L1_CACHE + KM_TYPE_NR * cpu;
 183         vaddr = __fix_to_virt(FIX_KMAP_BEGIN + idx);
 184         ptep = TOP_PTE(vaddr);
 185         pte = mk_pte(page, kmap_prot);
 186
 187         raw_local_irq_save(flags);
 188         (*depth)++;
 189         if (pte_val(*ptep) == pte_val(pte)) {
 190                 *saved_pte = pte;
 191         } else {
 192                 *saved_pte = *ptep;
 193                 set_pte_ext(ptep, pte, 0);
 194                 local_flush_tlb_kernel_page(vaddr);
 195         }
 196         raw_local_irq_restore(flags);
 197
 198         return (void *)vaddr;
 199 }
 200
 201 void kunmap_high_l1_vipt(struct page *page, pte_t saved_pte)
 202 {
 203         unsigned int idx, cpu = smp_processor_id();
 204         int *depth = &per_cpu(kmap_high_l1_vipt_depth, cpu);
 205         unsigned long vaddr, flags;
 206         pte_t pte, *ptep;
 207
 208         idx = KM_L1_CACHE + KM_TYPE_NR * cpu;
 209         vaddr = __fix_to_virt(FIX_KMAP_BEGIN + idx);
 210         ptep = TOP_PTE(vaddr);
 211         pte = mk_pte(page, kmap_prot);
 212
 213         BUG_ON(pte_val(*ptep) != pte_val(pte));
 214         BUG_ON(*depth <= 0);
 215
 216         raw_local_irq_save(flags);
 217         (*depth)--;
 218         if (*depth != 0 && pte_val(pte) != pte_val(saved_pte)) {
 219                 set_pte_ext(ptep, saved_pte, 0);
 220                 local_flush_tlb_kernel_page(vaddr);
 221         }
 222         raw_local_irq_restore(flags);
 223
 224         if (!in_interrupt())
 225                 preempt_enable();
 226 }
 227
 228 #endif  /* CONFIG_CPU_CACHE_VIPT */