tlb-urb.c

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/*
 * arch/sh/mm/tlb-urb.c
 *
 * TLB entry wiring helpers for URB-equipped parts.
 *
 * Copyright (C) 2010  Matt Fleming
 *
 * This file is subject to the terms and conditions of the GNU General Public
 * License.  See the file "COPYING" in the main directory of this archive
 * for more details.
 */
#include <linux/mm.h>
#include <linux/io.h>
#include <asm/tlb.h>
#include <asm/mmu_context.h>

/*
 * Load the entry for 'addr' into the TLB and wire the entry.
 */
void tlb_wire_entry(struct vm_area_struct *vma, unsigned long addr, pte_t pte)
{
    unsigned long status, flags;
    int urb;

    local_irq_save(flags);

    status = __raw_readl(MMUCR);
    urb = (status & MMUCR_URB) >> MMUCR_URB_SHIFT;
    status &= ~MMUCR_URC;

    /*
     * Make sure we're not trying to wire the last TLB entry slot.
     */
    BUG_ON(!--urb);

    urb = urb % MMUCR_URB_NENTRIES;

    /*
     * Insert this entry into the highest non-wired TLB slot (via
     * the URC field).
     */
    status |= (urb << MMUCR_URC_SHIFT);
    __raw_writel(status, MMUCR);
    ctrl_barrier();

    /* Load the entry into the TLB */
    __update_tlb(vma, addr, pte);

    /* ... and wire it up. */
    status = __raw_readl(MMUCR);

    status &= ~MMUCR_URB;
    status |= (urb << MMUCR_URB_SHIFT);

    __raw_writel(status, MMUCR);
    ctrl_barrier();

    local_irq_restore(flags);
}

/*
 * Unwire the last wired TLB entry.
 *
 * It should also be noted that it is not possible to wire and unwire
 * TLB entries in an arbitrary order. If you wire TLB entry N, followed
 * by entry N+1, you must unwire entry N+1 first, then entry N. In this
 * respect, it works like a stack or LIFO queue.
 */
void tlb_unwire_entry(void)
{
    unsigned long status, flags;
    int urb;

    local_irq_save(flags);

    status = __raw_readl(MMUCR);
    urb = (status & MMUCR_URB) >> MMUCR_URB_SHIFT;
    status &= ~MMUCR_URB;

    /*
     * Make sure we're not trying to unwire a TLB entry when none
     * have been wired.
     */
    BUG_ON(urb++ == MMUCR_URB_NENTRIES);

    urb = urb % MMUCR_URB_NENTRIES;

    status |= (urb << MMUCR_URB_SHIFT);
    __raw_writel(status, MMUCR);
    ctrl_barrier();

    local_irq_restore(flags);
}