uncached.c

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/*
 * 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.
 *
 * Copyright (C) 2005 Thiemo Seufer
 * Copyright (C) 2005  MIPS Technologies, Inc.  All rights reserved.
 *  Author: Maciej W. Rozycki <[email protected]>
 */

#include <linux/init.h>

#include <asm/addrspace.h>
#include <asm/bug.h>
#include <asm/cacheflush.h>

#ifndef CKSEG2
#define CKSEG2 CKSSEG
#endif
#ifndef TO_PHYS_MASK
#define TO_PHYS_MASK -1
#endif

/*
 * FUNC is executed in one of the uncached segments, depending on its
 * original address as follows:
 *
 * 1. If the original address is in CKSEG0 or CKSEG1, then the uncached
 *    segment used is CKSEG1.
 * 2. If the original address is in XKPHYS, then the uncached segment
 *    used is XKPHYS(2).
 * 3. Otherwise it's a bug.
 *
 * The same remapping is done with the stack pointer.  Stack handling
 * works because we don't handle stack arguments or more complex return
 * values, so we can avoid sharing the same stack area between a cached
 * and the uncached mode.
 */
unsigned long __cpuinit run_uncached(void *func)
{
    register long sp __asm__("$sp");
    register long ret __asm__("$2");
    long lfunc = (long)func, ufunc;
    long usp;

    if (sp >= (long)CKSEG0 && sp < (long)CKSEG2)
        usp = CKSEG1ADDR(sp);
#ifdef CONFIG_64BIT
    else if ((long long)sp >= (long long)PHYS_TO_XKPHYS(0, 0) &&
         (long long)sp < (long long)PHYS_TO_XKPHYS(8, 0))
        usp = PHYS_TO_XKPHYS(K_CALG_UNCACHED,
                     XKPHYS_TO_PHYS((long long)sp));
#endif
    else {
        BUG();
        usp = sp;
    }
    if (lfunc >= (long)CKSEG0 && lfunc < (long)CKSEG2)
        ufunc = CKSEG1ADDR(lfunc);
#ifdef CONFIG_64BIT
    else if ((long long)lfunc >= (long long)PHYS_TO_XKPHYS(0, 0) &&
         (long long)lfunc < (long long)PHYS_TO_XKPHYS(8, 0))
        ufunc = PHYS_TO_XKPHYS(K_CALG_UNCACHED,
                       XKPHYS_TO_PHYS((long long)lfunc));
#endif
    else {
        BUG();
        ufunc = lfunc;
    }

    __asm__ __volatile__ (
        "   move    $16, $sp\n"
        "   move    $sp, %1\n"
        "   jalr    %2\n"
        "   move    $sp, $16"
        : "=r" (ret)
        : "r" (usp), "r" (ufunc)
        : "$16", "$31");

    return ret;
}