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 #include <asm/cacheflush.h>
  16
  17 #ifndef CKSEG2
  18 #define CKSEG2 CKSSEG
  19 #endif
  20 #ifndef TO_PHYS_MASK
  21 #define TO_PHYS_MASK -1
  22 #endif
  23
  24 /*
  25  * FUNC is executed in one of the uncached segments, depending on its
  26  * original address as follows:
  27  *
  28  * 1. If the original address is in CKSEG0 or CKSEG1, then the uncached
  29  *    segment used is CKSEG1.
  30  * 2. If the original address is in XKPHYS, then the uncached segment
  31  *    used is XKPHYS(2).
  32  * 3. Otherwise it's a bug.
  33  *
  34  * The same remapping is done with the stack pointer.  Stack handling
  35  * works because we don't handle stack arguments or more complex return
  36  * values, so we can avoid sharing the same stack area between a cached
  37  * and the uncached mode.
  38  */
  39 unsigned long __init run_uncached(void *func)
  40 {
  41         register long sp __asm__("$sp");
  42         register long ret __asm__("$2");
  43         long lfunc = (long)func, ufunc;
  44         long usp;
  45
  46         if (sp >= (long)CKSEG0 && sp < (long)CKSEG2)
  47                 usp = CKSEG1ADDR(sp);
  48 #ifdef CONFIG_64BIT
  49         else if ((long long)sp >= (long long)PHYS_TO_XKPHYS(0, 0) &&
  50                  (long long)sp < (long long)PHYS_TO_XKPHYS(8, 0))
  51                 usp = PHYS_TO_XKPHYS(K_CALG_UNCACHED,
  52                                      XKPHYS_TO_PHYS((long long)sp));
  53 #endif
  54         else {
  55                 BUG();
  56                 usp = sp;
  57         }
  58         if (lfunc >= (long)CKSEG0 && lfunc < (long)CKSEG2)
  59                 ufunc = CKSEG1ADDR(lfunc);
  60 #ifdef CONFIG_64BIT
  61         else if ((long long)lfunc >= (long long)PHYS_TO_XKPHYS(0, 0) &&
  62                  (long long)lfunc < (long long)PHYS_TO_XKPHYS(8, 0))
  63                 ufunc = PHYS_TO_XKPHYS(K_CALG_UNCACHED,
  64                                        XKPHYS_TO_PHYS((long long)lfunc));
  65 #endif
  66         else {
  67                 BUG();
  68                 ufunc = lfunc;
  69         }
  70
  71         __asm__ __volatile__ (
  72                 "       move    $16, $sp\n"
  73                 "       move    $sp, %1\n"
  74                 "       jalr    %2\n"
  75                 "       move    $sp, $16"
  76                 : "=r" (ret)
  77                 : "r" (usp), "r" (ufunc)
  78                 : "$16", "$31");
  79
  80         return ret;
  81 }