arch/powerpc/mm/8xx_mmu.c

   1 /*
   2  * This file contains the routines for initializing the MMU
   3  * on the 8xx series of chips.
   4  *  -- christophe
   5  *
   6  *  Derived from arch/powerpc/mm/40x_mmu.c:
   7  *
   8  *  This program is free software; you can redistribute it and/or
   9  *  modify it under the terms of the GNU General Public License
  10  *  as published by the Free Software Foundation; either version
  11  *  2 of the License, or (at your option) any later version.
  12  *
  13  */
  14
  15 #include <linux/memblock.h>
  16
  17 #include "mmu_decl.h"
  18
  19 extern int __map_without_ltlbs;
  20 /*
  21  * MMU_init_hw does the chip-specific initialization of the MMU hardware.
  22  */
  23 void __init MMU_init_hw(void)
  24 {
  25         /* Nothing to do for the time being but keep it similar to other PPC */
  26 }
  27
  28 #define LARGE_PAGE_SIZE_4M      (1<<22)
  29 #define LARGE_PAGE_SIZE_8M      (1<<23)
  30 #define LARGE_PAGE_SIZE_64M     (1<<26)
  31
  32 unsigned long __init mmu_mapin_ram(unsigned long top)
  33 {
  34         unsigned long v, s, mapped;
  35         phys_addr_t p;
  36
  37         v = KERNELBASE;
  38         p = 0;
  39         s = top;
  40
  41         if (__map_without_ltlbs)
  42                 return 0;
  43
  44 #ifdef CONFIG_PPC_4K_PAGES
  45         while (s >= LARGE_PAGE_SIZE_8M) {
  46                 pmd_t *pmdp;
  47                 unsigned long val = p | MD_PS8MEG;
  48
  49                 pmdp = pmd_offset(pud_offset(pgd_offset_k(v), v), v);
  50                 *pmdp++ = __pmd(val);
  51                 *pmdp++ = __pmd(val + LARGE_PAGE_SIZE_4M);
  52
  53                 v += LARGE_PAGE_SIZE_8M;
  54                 p += LARGE_PAGE_SIZE_8M;
  55                 s -= LARGE_PAGE_SIZE_8M;
  56         }
  57 #else /* CONFIG_PPC_16K_PAGES */
  58         while (s >= LARGE_PAGE_SIZE_64M) {
  59                 pmd_t *pmdp;
  60                 unsigned long val = p | MD_PS8MEG;
  61
  62                 pmdp = pmd_offset(pud_offset(pgd_offset_k(v), v), v);
  63                 *pmdp++ = __pmd(val);
  64
  65                 v += LARGE_PAGE_SIZE_64M;
  66                 p += LARGE_PAGE_SIZE_64M;
  67                 s -= LARGE_PAGE_SIZE_64M;
  68         }
  69 #endif
  70
  71         mapped = top - s;
  72
  73         /* If the size of RAM is not an exact power of two, we may not
  74          * have covered RAM in its entirety with 8 MiB
  75          * pages. Consequently, restrict the top end of RAM currently
  76          * allocable so that calls to the MEMBLOCK to allocate PTEs for "tail"
  77          * coverage with normal-sized pages (or other reasons) do not
  78          * attempt to allocate outside the allowed range.
  79          */
  80         memblock_set_current_limit(mapped);
  81
  82         return mapped;
  83 }
  84
  85 void setup_initial_memory_limit(phys_addr_t first_memblock_base,
  86                                 phys_addr_t first_memblock_size)
  87 {
  88         /* We don't currently support the first MEMBLOCK not mapping 0
  89          * physical on those processors
  90          */
  91         BUG_ON(first_memblock_base != 0);
  92
  93 #ifdef CONFIG_PIN_TLB
  94         /* 8xx can only access 24MB at the moment */
  95         memblock_set_current_limit(min_t(u64, first_memblock_size, 0x01800000));
  96 #else
  97         /* 8xx can only access 8MB at the moment */
  98         memblock_set_current_limit(min_t(u64, first_memblock_size, 0x00800000));
  99 #endif
 100 }