arch/i386/mm/boot_ioremap.c

   1 /*
   2  * arch/i386/mm/boot_ioremap.c
   3  *
   4  * Re-map functions for early boot-time before paging_init() when the
   5  * boot-time pagetables are still in use
   6  *
   7  * Written by Dave Hansen <haveblue@us.ibm.com>
   8  */
   9
  10
  11 /*
  12  * We need to use the 2-level pagetable functions, but CONFIG_X86_PAE
  13  * keeps that from happenning.  If anyone has a better way, I'm listening.
  14  *
  15  * boot_pte_t is defined only if this all works correctly
  16  */
  17
  18 #undef CONFIG_X86_PAE
  19 #include <asm/page.h>
  20 #include <asm/pgtable.h>
  21 #include <asm/tlbflush.h>
  22 #include <linux/init.h>
  23 #include <linux/stddef.h>
  24
  25 /*
  26  * I'm cheating here.  It is known that the two boot PTE pages are
  27  * allocated next to each other.  I'm pretending that they're just
  28  * one big array.
  29  */
  30
  31 #define BOOT_PTE_PTRS (PTRS_PER_PTE*2)
  32
  33 static unsigned long boot_pte_index(unsigned long vaddr)
  34 {
  35         return __pa(vaddr) >> PAGE_SHIFT;
  36 }
  37
  38 static inline boot_pte_t* boot_vaddr_to_pte(void *address)
  39 {
  40         boot_pte_t* boot_pg = (boot_pte_t*)pg0;
  41         return &boot_pg[boot_pte_index((unsigned long)address)];
  42 }
  43
  44 /*
  45  * This is only for a caller who is clever enough to page-align
  46  * phys_addr and virtual_source, and who also has a preference
  47  * about which virtual address from which to steal ptes
  48  */
  49 static void __boot_ioremap(unsigned long phys_addr, unsigned long nrpages,
  50                     void* virtual_source)
  51 {
  52         boot_pte_t* pte;
  53         int i;
  54         char *vaddr = virtual_source;
  55
  56         pte = boot_vaddr_to_pte(virtual_source);
  57         for (i=0; i < nrpages; i++, phys_addr += PAGE_SIZE, pte++) {
  58                 set_pte(pte, pfn_pte(phys_addr>>PAGE_SHIFT, PAGE_KERNEL));
  59                 __flush_tlb_one(&vaddr[i*PAGE_SIZE]);
  60         }
  61 }
  62
  63 /* the virtual space we're going to remap comes from this array */
  64 #define BOOT_IOREMAP_PAGES 4
  65 #define BOOT_IOREMAP_SIZE (BOOT_IOREMAP_PAGES*PAGE_SIZE)
  66 static __initdata char boot_ioremap_space[BOOT_IOREMAP_SIZE]
  67                        __attribute__ ((aligned (PAGE_SIZE)));
  68
  69 /*
  70  * This only applies to things which need to ioremap before paging_init()
  71  * bt_ioremap() and plain ioremap() are both useless at this point.
  72  *
  73  * When used, we're still using the boot-time pagetables, which only
  74  * have 2 PTE pages mapping the first 8MB
  75  *
  76  * There is no unmap.  The boot-time PTE pages aren't used after boot.
  77  * If you really want the space back, just remap it yourself.
  78  * boot_ioremap(&ioremap_space-PAGE_OFFSET, BOOT_IOREMAP_SIZE)
  79  */
  80 __init void* boot_ioremap(unsigned long phys_addr, unsigned long size)
  81 {
  82         unsigned long last_addr, offset;
  83         unsigned int nrpages;
  84
  85         last_addr = phys_addr + size - 1;
  86
  87         /* page align the requested address */
  88         offset = phys_addr & ~PAGE_MASK;
  89         phys_addr &= PAGE_MASK;
  90         size = PAGE_ALIGN(last_addr) - phys_addr;
  91
  92         nrpages = size >> PAGE_SHIFT;
  93         if (nrpages > BOOT_IOREMAP_PAGES)
  94                 return NULL;
  95
  96         __boot_ioremap(phys_addr, nrpages, boot_ioremap_space);
  97
  98         return &boot_ioremap_space[offset];
  99 }