arch/mips/lib/uncached.c

   1 /*
   2  * This file is subject to the terms and conditions of the GNU General Public
   3  * License.  See the file "COPYING" in the main directory of this archive
   4  * for more details.
   5  *
   6  * Copyright (C) 2005 Thiemo Seufer
   7  * Copyright (C) 2005  MIPS Technologies, Inc.  All rights reserved.
   8  *      Author: Maciej W. Rozycki <macro@mips.com>
   9  */
  10
  11 #include <linux/init.h>
  12
  13 #include <asm/addrspace.h>
  14 #include <asm/bug.h>
  15
  16 #ifndef CKSEG2
  17 #define CKSEG2 CKSSEG
  18 #endif
  19 #ifndef TO_PHYS_MASK
  20 #define TO_PHYS_MASK -1
  21 #endif
  22
  23 /*
  24  * FUNC is executed in one of the uncached segments, depending on its
  25  * original address as follows:
  26  *
  27  * 1. If the original address is in CKSEG0 or CKSEG1, then the uncached
  28  *    segment used is CKSEG1.
  29  * 2. If the original address is in XKPHYS, then the uncached segment
  30  *    used is XKPHYS(2).
  31  * 3. Otherwise it's a bug.
  32  *
  33  * The same remapping is done with the stack pointer.  Stack handling
  34  * works because we don't handle stack arguments or more complex return
  35  * values, so we can avoid sharing the same stack area between a cached
  36  * and the uncached mode.
  37  */
  38 unsigned long __init run_uncached(void *func)
  39 {
  40         register long sp __asm__("$sp");
  41         register long ret __asm__("$2");
  42         long lfunc = (long)func, ufunc;
  43         long usp;
  44
  45         if (sp >= (long)CKSEG0 && sp < (long)CKSEG2)
  46                 usp = CKSEG1ADDR(sp);
  47         else if ((long long)sp >= (long long)PHYS_TO_XKPHYS(0LL, 0) &&
  48                  (long long)sp < (long long)PHYS_TO_XKPHYS(8LL, 0))
  49                 usp = PHYS_TO_XKPHYS((long long)K_CALG_UNCACHED,
  50                                      XKPHYS_TO_PHYS((long long)sp));
  51         else {
  52                 BUG();
  53                 usp = sp;
  54         }
  55         if (lfunc >= (long)CKSEG0 && lfunc < (long)CKSEG2)
  56                 ufunc = CKSEG1ADDR(lfunc);
  57         else if ((long long)lfunc >= (long long)PHYS_TO_XKPHYS(0LL, 0) &&
  58                  (long long)lfunc < (long long)PHYS_TO_XKPHYS(8LL, 0))
  59                 ufunc = PHYS_TO_XKPHYS((long long)K_CALG_UNCACHED,
  60                                        XKPHYS_TO_PHYS((long long)lfunc));
  61         else {
  62                 BUG();
  63                 ufunc = lfunc;
  64         }
  65
  66         __asm__ __volatile__ (
  67                 "       move    $16, $sp\n"
  68                 "       move    $sp, %1\n"
  69                 "       jalr    %2\n"
  70                 "       move    $sp, $16"
  71                 : "=r" (ret)
  72                 : "r" (usp), "r" (ufunc)
  73                 : "$16", "$31");
  74
  75         return ret;
  76 }