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highmem.c

/*
 * arch/arm/mm/highmem.c -- ARM highmem support
 *
 * Author:  Nicolas Pitre
 * Created: september 8, 2008
 * Copyright:     Marvell Semiconductors Inc.
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 */

#include <linux/module.h>
#include <linux/highmem.h>
#include <linux/interrupt.h>
#include <asm/fixmap.h>
#include <asm/cacheflush.h>
#include <asm/tlbflush.h>
#include "mm.h"

void *kmap(struct page *page)
{
      might_sleep();
      if (!PageHighMem(page))
            return page_address(page);
      return kmap_high(page);
}
EXPORT_SYMBOL(kmap);

void kunmap(struct page *page)
{
      BUG_ON(in_interrupt());
      if (!PageHighMem(page))
            return;
      kunmap_high(page);
}
EXPORT_SYMBOL(kunmap);

void *__kmap_atomic(struct page *page)
{
      unsigned int idx;
      unsigned long vaddr;
      void *kmap;
      int type;

      pagefault_disable();
      if (!PageHighMem(page))
            return page_address(page);

#ifdef CONFIG_DEBUG_HIGHMEM
      /*
       * There is no cache coherency issue when non VIVT, so force the
       * dedicated kmap usage for better debugging purposes in that case.
       */
      if (!cache_is_vivt())
            kmap = NULL;
      else
#endif
            kmap = kmap_high_get(page);
      if (kmap)
            return kmap;

      type = kmap_atomic_idx_push();

      idx = type + KM_TYPE_NR * smp_processor_id();
      vaddr = __fix_to_virt(FIX_KMAP_BEGIN + idx);
#ifdef CONFIG_DEBUG_HIGHMEM
      /*
       * With debugging enabled, kunmap_atomic forces that entry to 0.
       * Make sure it was indeed properly unmapped.
       */
      BUG_ON(!pte_none(*(TOP_PTE(vaddr))));
#endif
      set_pte_ext(TOP_PTE(vaddr), mk_pte(page, kmap_prot), 0);
      /*
       * When debugging is off, kunmap_atomic leaves the previous mapping
       * in place, so this TLB flush ensures the TLB is updated with the
       * new mapping.
       */
      local_flush_tlb_kernel_page(vaddr);

      return (void *)vaddr;
}
EXPORT_SYMBOL(__kmap_atomic);

void __kunmap_atomic(void *kvaddr)
{
      unsigned long vaddr = (unsigned long) kvaddr & PAGE_MASK;
      int idx, type;

      if (kvaddr >= (void *)FIXADDR_START) {
            type = kmap_atomic_idx();
            idx = type + KM_TYPE_NR * smp_processor_id();

            if (cache_is_vivt())
                  __cpuc_flush_dcache_area((void *)vaddr, PAGE_SIZE);
#ifdef CONFIG_DEBUG_HIGHMEM
            BUG_ON(vaddr != __fix_to_virt(FIX_KMAP_BEGIN + idx));
            set_pte_ext(TOP_PTE(vaddr), __pte(0), 0);
            local_flush_tlb_kernel_page(vaddr);
#else
            (void) idx;  /* to kill a warning */
#endif
            kmap_atomic_idx_pop();
      } else if (vaddr >= PKMAP_ADDR(0) && vaddr < PKMAP_ADDR(LAST_PKMAP)) {
            /* this address was obtained through kmap_high_get() */
            kunmap_high(pte_page(pkmap_page_table[PKMAP_NR(vaddr)]));
      }
      pagefault_enable();
}
EXPORT_SYMBOL(__kunmap_atomic);

void *kmap_atomic_pfn(unsigned long pfn)
{
      unsigned long vaddr;
      int idx, type;

      pagefault_disable();

      type = kmap_atomic_idx_push();
      idx = type + KM_TYPE_NR * smp_processor_id();
      vaddr = __fix_to_virt(FIX_KMAP_BEGIN + idx);
#ifdef CONFIG_DEBUG_HIGHMEM
      BUG_ON(!pte_none(*(TOP_PTE(vaddr))));
#endif
      set_pte_ext(TOP_PTE(vaddr), pfn_pte(pfn, kmap_prot), 0);
      local_flush_tlb_kernel_page(vaddr);

      return (void *)vaddr;
}

struct page *kmap_atomic_to_page(const void *ptr)
{
      unsigned long vaddr = (unsigned long)ptr;
      pte_t *pte;

      if (vaddr < FIXADDR_START)
            return virt_to_page(ptr);

      pte = TOP_PTE(vaddr);
      return pte_page(*pte);
}

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