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