copypage-xscale.c

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/*
 *  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"

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

static DEFINE_RAW_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, struct vm_area_struct *vma)
{
    void *kto = kmap_atomic(to);

    if (!test_and_set_bit(PG_dcache_clean, &from->flags))
        __flush_dcache_page(page_mapping(from), from);

    raw_spin_lock(&minicache_lock);

    set_top_pte(COPYPAGE_MINICACHE, mk_pte(from, minicache_pgprot));

    mc_copy_user_page((void *)COPYPAGE_MINICACHE, kto);

    raw_spin_unlock(&minicache_lock);

    kunmap_atomic(kto);
}

/*
 * XScale optimised clear_user_page
 */
void
xscale_mc_clear_user_highpage(struct page *page, unsigned long vaddr)
{
    void *ptr, *kaddr = kmap_atomic(page);
    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);
}

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,
};