arch/powerpc/mm/40x_mmu.c

   1 /*
   2  * This file contains the routines for initializing the MMU
   3  * on the 4xx series of chips.
   4  *  -- paulus
   5  *
   6  *  Derived from arch/ppc/mm/init.c:
   7  *    Copyright (C) 1995-1996 Gary Thomas (gdt@linuxppc.org)
   8  *
   9  *  Modifications by Paul Mackerras (PowerMac) (paulus@cs.anu.edu.au)
  10  *  and Cort Dougan (PReP) (cort@cs.nmt.edu)
  11  *    Copyright (C) 1996 Paul Mackerras
  12  *
  13  *  Derived from "arch/i386/mm/init.c"
  14  *    Copyright (C) 1991, 1992, 1993, 1994  Linus Torvalds
  15  *
  16  *  This program is free software; you can redistribute it and/or
  17  *  modify it under the terms of the GNU General Public License
  18  *  as published by the Free Software Foundation; either version
  19  *  2 of the License, or (at your option) any later version.
  20  *
  21  */
  22
  23 #include <linux/signal.h>
  24 #include <linux/sched.h>
  25 #include <linux/kernel.h>
  26 #include <linux/errno.h>
  27 #include <linux/string.h>
  28 #include <linux/types.h>
  29 #include <linux/ptrace.h>
  30 #include <linux/mman.h>
  31 #include <linux/mm.h>
  32 #include <linux/swap.h>
  33 #include <linux/stddef.h>
  34 #include <linux/vmalloc.h>
  35 #include <linux/init.h>
  36 #include <linux/delay.h>
  37 #include <linux/highmem.h>
  38 #include <linux/memblock.h>
  39
  40 #include <asm/pgalloc.h>
  41 #include <asm/prom.h>
  42 #include <asm/io.h>
  43 #include <asm/mmu_context.h>
  44 #include <asm/pgtable.h>
  45 #include <asm/mmu.h>
  46 #include <linux/uaccess.h>
  47 #include <asm/smp.h>
  48 #include <asm/bootx.h>
  49 #include <asm/machdep.h>
  50 #include <asm/setup.h>
  51
  52 #include "mmu_decl.h"
  53
  54 extern int __map_without_ltlbs;
  55 /*
  56  * MMU_init_hw does the chip-specific initialization of the MMU hardware.
  57  */
  58 void __init MMU_init_hw(void)
  59 {
  60         /*
  61          * The Zone Protection Register (ZPR) defines how protection will
  62          * be applied to every page which is a member of a given zone. At
  63          * present, we utilize only two of the 4xx's zones.
  64          * The zone index bits (of ZSEL) in the PTE are used for software
  65          * indicators, except the LSB.  For user access, zone 1 is used,
  66          * for kernel access, zone 0 is used.  We set all but zone 1
  67          * to zero, allowing only kernel access as indicated in the PTE.
  68          * For zone 1, we set a 01 binary (a value of 10 will not work)
  69          * to allow user access as indicated in the PTE.  This also allows
  70          * kernel access as indicated in the PTE.
  71          */
  72
  73         mtspr(SPRN_ZPR, 0x10000000);
  74
  75         flush_instruction_cache();
  76
  77         /*
  78          * Set up the real-mode cache parameters for the exception vector
  79          * handlers (which are run in real-mode).
  80          */
  81
  82         mtspr(SPRN_DCWR, 0x00000000);   /* All caching is write-back */
  83
  84         /*
  85          * Cache instruction and data space where the exception
  86          * vectors and the kernel live in real-mode.
  87          */
  88
  89         mtspr(SPRN_DCCR, 0xFFFF0000);   /* 2GByte of data space at 0x0. */
  90         mtspr(SPRN_ICCR, 0xFFFF0000);   /* 2GByte of instr. space at 0x0. */
  91 }
  92
  93 #define LARGE_PAGE_SIZE_16M     (1<<24)
  94 #define LARGE_PAGE_SIZE_4M      (1<<22)
  95
  96 unsigned long __init mmu_mapin_ram(unsigned long top)
  97 {
  98         unsigned long v, s, mapped;
  99         phys_addr_t p;
 100
 101         v = KERNELBASE;
 102         p = 0;
 103         s = total_lowmem;
 104
 105         if (__map_without_ltlbs)
 106                 return 0;
 107
 108         while (s >= LARGE_PAGE_SIZE_16M) {
 109                 pmd_t *pmdp;
 110                 unsigned long val = p | _PMD_SIZE_16M | _PAGE_EXEC | _PAGE_HWWRITE;
 111
 112                 pmdp = pmd_offset(pud_offset(pgd_offset_k(v), v), v);
 113                 *pmdp++ = __pmd(val);
 114                 *pmdp++ = __pmd(val);
 115                 *pmdp++ = __pmd(val);
 116                 *pmdp++ = __pmd(val);
 117
 118                 v += LARGE_PAGE_SIZE_16M;
 119                 p += LARGE_PAGE_SIZE_16M;
 120                 s -= LARGE_PAGE_SIZE_16M;
 121         }
 122
 123         while (s >= LARGE_PAGE_SIZE_4M) {
 124                 pmd_t *pmdp;
 125                 unsigned long val = p | _PMD_SIZE_4M | _PAGE_EXEC | _PAGE_HWWRITE;
 126
 127                 pmdp = pmd_offset(pud_offset(pgd_offset_k(v), v), v);
 128                 *pmdp = __pmd(val);
 129
 130                 v += LARGE_PAGE_SIZE_4M;
 131                 p += LARGE_PAGE_SIZE_4M;
 132                 s -= LARGE_PAGE_SIZE_4M;
 133         }
 134
 135         mapped = total_lowmem - s;
 136
 137         /* If the size of RAM is not an exact power of two, we may not
 138          * have covered RAM in its entirety with 16 and 4 MiB
 139          * pages. Consequently, restrict the top end of RAM currently
 140          * allocable so that calls to the MEMBLOCK to allocate PTEs for "tail"
 141          * coverage with normal-sized pages (or other reasons) do not
 142          * attempt to allocate outside the allowed range.
 143          */
 144         memblock_set_current_limit(mapped);
 145
 146         return mapped;
 147 }
 148
 149 void setup_initial_memory_limit(phys_addr_t first_memblock_base,
 150                                 phys_addr_t first_memblock_size)
 151 {
 152         /* We don't currently support the first MEMBLOCK not mapping 0
 153          * physical on those processors
 154          */
 155         BUG_ON(first_memblock_base != 0);
 156
 157         /* 40x can only access 16MB at the moment (see head_40x.S) */
 158         memblock_set_current_limit(min_t(u64, first_memblock_size, 0x00800000));
 159 }