arch/arm26/mm/memc.c

   1 /*
   2  *  linux/arch/arm26/mm/memc.c
   3  *
   4  *  Copyright (C) 1998-2000 Russell King
   5  *
   6  * This program is free software; you can redistribute it and/or modify
   7  * it under the terms of the GNU General Public License version 2 as
   8  * published by the Free Software Foundation.
   9  *
  10  *  Page table sludge for older ARM processor architectures.
  11  */
  12 #include <linux/sched.h>
  13 #include <linux/mm.h>
  14 #include <linux/init.h>
  15 #include <linux/bootmem.h>
  16
  17 #include <asm/pgtable.h>
  18 #include <asm/pgalloc.h>
  19 #include <asm/page.h>
  20 #include <asm/memory.h>
  21 #include <asm/hardware.h>
  22
  23 #include <asm/map.h>
  24
  25 #define MEMC_TABLE_SIZE (256*sizeof(unsigned long))
  26
  27 struct kmem_cache *pte_cache, *pgd_cache;
  28 int page_nr;
  29
  30 /*
  31  * Allocate space for a page table and a MEMC table.
  32  * Note that we place the MEMC
  33  * table before the page directory.  This means we can
  34  * easily get to both tightly-associated data structures
  35  * with a single pointer.
  36  */
  37 static inline pgd_t *alloc_pgd_table(void)
  38 {
  39         void *pg2k = kmem_cache_alloc(pgd_cache, GFP_KERNEL);
  40
  41         if (pg2k)
  42                 pg2k += MEMC_TABLE_SIZE;
  43
  44         return (pgd_t *)pg2k;
  45 }
  46
  47 /*
  48  * Free a page table. this function is the counterpart to get_pgd_slow
  49  * below, not alloc_pgd_table above.
  50  */
  51 void free_pgd_slow(pgd_t *pgd)
  52 {
  53         unsigned long tbl = (unsigned long)pgd;
  54
  55         tbl -= MEMC_TABLE_SIZE;
  56
  57         kmem_cache_free(pgd_cache, (void *)tbl);
  58 }
  59
  60 /*
  61  * Allocate a new pgd and fill it in ready for use
  62  *
  63  * A new tasks pgd is completely empty (all pages !present) except for:
  64  *
  65  * o The machine vectors at virtual address 0x0
  66  * o The vmalloc region at the top of address space
  67  *
  68  */
  69 #define FIRST_KERNEL_PGD_NR     (FIRST_USER_PGD_NR + USER_PTRS_PER_PGD)
  70
  71 pgd_t *get_pgd_slow(struct mm_struct *mm)
  72 {
  73         pgd_t *new_pgd, *init_pgd;
  74         pmd_t *new_pmd, *init_pmd;
  75         pte_t *new_pte, *init_pte;
  76
  77         new_pgd = alloc_pgd_table();
  78         if (!new_pgd)
  79                 goto no_pgd;
  80
  81         /*
  82          * On ARM, first page must always be allocated since it contains
  83          * the machine vectors.
  84          */
  85         new_pmd = pmd_alloc(mm, new_pgd, 0);
  86         if (!new_pmd)
  87                 goto no_pmd;
  88
  89         new_pte = pte_alloc_map(mm, new_pmd, 0);
  90         if (!new_pte)
  91                 goto no_pte;
  92
  93         init_pgd = pgd_offset(&init_mm, 0);
  94         init_pmd = pmd_offset(init_pgd, 0);
  95         init_pte = pte_offset(init_pmd, 0);
  96
  97         set_pte(new_pte, *init_pte);
  98         pte_unmap(new_pte);
  99
 100         /*
 101          * the page table entries are zeroed
 102          * when the table is created. (see the cache_ctor functions below)
 103          * Now we need to plonk the kernel (vmalloc) area at the end of
 104          * the address space. We copy this from the init thread, just like
 105          * the init_pte we copied above...
 106          */
 107         memcpy(new_pgd + FIRST_KERNEL_PGD_NR, init_pgd + FIRST_KERNEL_PGD_NR,
 108                 (PTRS_PER_PGD - FIRST_KERNEL_PGD_NR) * sizeof(pgd_t));
 109
 110         /* update MEMC tables */
 111         cpu_memc_update_all(new_pgd);
 112         return new_pgd;
 113
 114 no_pte:
 115         pmd_free(new_pmd);
 116 no_pmd:
 117         free_pgd_slow(new_pgd);
 118 no_pgd:
 119         return NULL;
 120 }
 121
 122 /*
 123  * No special code is required here.
 124  */
 125 void setup_mm_for_reboot(char mode)
 126 {
 127 }
 128
 129 /*
 130  * This contains the code to setup the memory map on an ARM2/ARM250/ARM3
 131  *  o swapper_pg_dir = 0x0207d000
 132  *  o kernel proper starts at 0x0208000
 133  *  o create (allocate) a pte to contain the machine vectors
 134  *  o populate the pte (points to 0x02078000) (FIXME - is it zeroed?)
 135  *  o populate the init tasks page directory (pgd) with the new pte
 136  *  o zero the rest of the init tasks pgdir (FIXME - what about vmalloc?!)
 137  */
 138 void __init memtable_init(struct meminfo *mi)
 139 {
 140         pte_t *pte;
 141         int i;
 142
 143         page_nr = max_low_pfn;
 144
 145         pte = alloc_bootmem_low_pages(PTRS_PER_PTE * sizeof(pte_t));
 146         pte[0] = mk_pte_phys(PAGE_OFFSET + SCREEN_SIZE, PAGE_READONLY);
 147         pmd_populate(&init_mm, pmd_offset(swapper_pg_dir, 0), pte);
 148
 149         for (i = 1; i < PTRS_PER_PGD; i++)
 150                 pgd_val(swapper_pg_dir[i]) = 0;
 151 }
 152
 153 void __init iotable_init(struct map_desc *io_desc)
 154 {
 155         /* nothing to do */
 156 }
 157
 158 /*
 159  * We never have holes in the memmap
 160  */
 161 void __init create_memmap_holes(struct meminfo *mi)
 162 {
 163 }
 164
 165 static void pte_cache_ctor(void *pte, struct kmem_cache *cache, unsigned long flags)
 166 {
 167         memzero(pte, sizeof(pte_t) * PTRS_PER_PTE);
 168 }
 169
 170 static void pgd_cache_ctor(void *pgd, struct kmem_cache *cache, unsigned long flags)
 171 {
 172         memzero(pgd + MEMC_TABLE_SIZE, USER_PTRS_PER_PGD * sizeof(pgd_t));
 173 }
 174
 175 void __init pgtable_cache_init(void)
 176 {
 177         pte_cache = kmem_cache_create("pte-cache",
 178                                 sizeof(pte_t) * PTRS_PER_PTE,
 179                                 0, 0, pte_cache_ctor, NULL);
 180         if (!pte_cache)
 181                 BUG();
 182
 183         pgd_cache = kmem_cache_create("pgd-cache", MEMC_TABLE_SIZE +
 184                                 sizeof(pgd_t) * PTRS_PER_PGD,
 185                                 0, 0, pgd_cache_ctor, NULL);
 186         if (!pgd_cache)
 187                 BUG();
 188 }