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copypage-xscale.c

/*
 *  linux/arch/arm/lib/copypage-xscale.S
 *
 *  Copyright (C) 1995-2005 Russell King
 *
 * 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.
 *
 * This handles the mini data cache, as found on SA11x0 and XScale
 * processors.  When we copy a user page page, we map it in such a way
 * that accesses to this page will not touch the main data cache, but
 * will be cached in the mini data cache.  This prevents us thrashing
 * the main data cache on page faults.
 */
#include <linux/init.h>
#include <linux/mm.h>
#include <linux/highmem.h>

#include <asm/pgtable.h>
#include <asm/tlbflush.h>
#include <asm/cacheflush.h>

#include "mm.h"

/*
 * 0xffff8000 to 0xffffffff is reserved for any ARM architecture
 * specific hacks for copying pages efficiently.
 */
#define COPYPAGE_MINICACHE    0xffff8000

#define minicache_pgprot __pgprot(L_PTE_PRESENT | L_PTE_YOUNG | \
                          L_PTE_MT_MINICACHE)

static DEFINE_SPINLOCK(minicache_lock);

/*
 * XScale mini-dcache optimised copy_user_highpage
 *
 * We flush the destination cache lines just before we write the data into the
 * corresponding address.  Since the Dcache is read-allocate, this removes the
 * Dcache aliasing issue.  The writes will be forwarded to the write buffer,
 * and merged as appropriate.
 */
static void __naked
mc_copy_user_page(void *from, void *to)
{
      /*
       * Strangely enough, best performance is achieved
       * when prefetching destination as well.  (NP)
       */
      asm volatile(
      "stmfd      sp!, {r4, r5, lr}       \n\
      mov   lr, %2                        \n\
      pld   [r0, #0]                \n\
      pld   [r0, #32]               \n\
      pld   [r1, #0]                \n\
      pld   [r1, #32]               \n\
1:    pld   [r0, #64]               \n\
      pld   [r0, #96]               \n\
      pld   [r1, #64]               \n\
      pld   [r1, #96]               \n\
2:    ldrd  r2, [r0], #8                  \n\
      ldrd  r4, [r0], #8                  \n\
      mov   ip, r1                        \n\
      strd  r2, [r1], #8                  \n\
      ldrd  r2, [r0], #8                  \n\
      strd  r4, [r1], #8                  \n\
      ldrd  r4, [r0], #8                  \n\
      strd  r2, [r1], #8                  \n\
      strd  r4, [r1], #8                  \n\
      mcr   p15, 0, ip, c7, c10, 1        @ clean D line\n\
      ldrd  r2, [r0], #8                  \n\
      mcr   p15, 0, ip, c7, c6, 1         @ invalidate D line\n\
      ldrd  r4, [r0], #8                  \n\
      mov   ip, r1                        \n\
      strd  r2, [r1], #8                  \n\
      ldrd  r2, [r0], #8                  \n\
      strd  r4, [r1], #8                  \n\
      ldrd  r4, [r0], #8                  \n\
      strd  r2, [r1], #8                  \n\
      strd  r4, [r1], #8                  \n\
      mcr   p15, 0, ip, c7, c10, 1        @ clean D line\n\
      subs  lr, lr, #1              \n\
      mcr   p15, 0, ip, c7, c6, 1         @ invalidate D line\n\
      bgt   1b                      \n\
      beq   2b                      \n\
      ldmfd sp!, {r4, r5, pc}       "
      :
      : "r" (from), "r" (to), "I" (PAGE_SIZE / 64 - 1));
}

void xscale_mc_copy_user_highpage(struct page *to, struct page *from,
      unsigned long vaddr)
{
      void *kto = kmap_atomic(to, KM_USER1);

      if (test_and_clear_bit(PG_dcache_dirty, &from->flags))
            __flush_dcache_page(page_mapping(from), from);

      spin_lock(&minicache_lock);

      set_pte_ext(TOP_PTE(COPYPAGE_MINICACHE), pfn_pte(page_to_pfn(from), minicache_pgprot), 0);
      flush_tlb_kernel_page(COPYPAGE_MINICACHE);

      mc_copy_user_page((void *)COPYPAGE_MINICACHE, kto);

      spin_unlock(&minicache_lock);

      kunmap_atomic(kto, KM_USER1);
}

/*
 * XScale optimised clear_user_page
 */
void
xscale_mc_clear_user_highpage(struct page *page, unsigned long vaddr)
{
      void *ptr, *kaddr = kmap_atomic(page, KM_USER0);
      asm volatile(
      "mov  r1, %2                        \n\
      mov   r2, #0                        \n\
      mov   r3, #0                        \n\
1:    mov   ip, %0                        \n\
      strd  r2, [%0], #8                  \n\
      strd  r2, [%0], #8                  \n\
      strd  r2, [%0], #8                  \n\
      strd  r2, [%0], #8                  \n\
      mcr   p15, 0, ip, c7, c10, 1        @ clean D line\n\
      subs  r1, r1, #1              \n\
      mcr   p15, 0, ip, c7, c6, 1         @ invalidate D line\n\
      bne   1b"
      : "=r" (ptr)
      : "0" (kaddr), "I" (PAGE_SIZE / 32)
      : "r1", "r2", "r3", "ip");
      kunmap_atomic(kaddr, KM_USER0);
}

struct cpu_user_fns xscale_mc_user_fns __initdata = {
      .cpu_clear_user_highpage = xscale_mc_clear_user_highpage,
      .cpu_copy_user_highpage = xscale_mc_copy_user_highpage,
};

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