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 #undef CONFIG_PARAVIRT
  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
  34 static unsigned long boot_pte_index(unsigned long vaddr)
  35 {
  36         return __pa(vaddr) >> PAGE_SHIFT;
  37 }
  38
  39 static inline boot_pte_t* boot_vaddr_to_pte(void *address)
  40 {
  41         boot_pte_t* boot_pg = (boot_pte_t*)pg0;
  42         return &boot_pg[boot_pte_index((unsigned long)address)];
  43 }
  44
  45 /*
  46  * This is only for a caller who is clever enough to page-align
  47  * phys_addr and virtual_source, and who also has a preference
  48  * about which virtual address from which to steal ptes
  49  */
  50 static void __boot_ioremap(unsigned long phys_addr, unsigned long nrpages,
  51                     void* virtual_source)
  52 {
  53         boot_pte_t* pte;
  54         int i;
  55         char *vaddr = virtual_source;
  56
  57         pte = boot_vaddr_to_pte(virtual_source);
  58         for (i=0; i < nrpages; i++, phys_addr += PAGE_SIZE, pte++) {
  59                 set_pte(pte, pfn_pte(phys_addr>>PAGE_SHIFT, PAGE_KERNEL));
  60                 __flush_tlb_one(&vaddr[i*PAGE_SIZE]);
  61         }
  62 }
  63
  64 /* the virtual space we're going to remap comes from this array */
  65 #define BOOT_IOREMAP_PAGES 4
  66 #define BOOT_IOREMAP_SIZE (BOOT_IOREMAP_PAGES*PAGE_SIZE)
  67 static __initdata char boot_ioremap_space[BOOT_IOREMAP_SIZE]
  68                        __attribute__ ((aligned (PAGE_SIZE)));
  69
  70 /*
  71  * This only applies to things which need to ioremap before paging_init()
  72  * bt_ioremap() and plain ioremap() are both useless at this point.
  73  *
  74  * When used, we're still using the boot-time pagetables, which only
  75  * have 2 PTE pages mapping the first 8MB
  76  *
  77  * There is no unmap.  The boot-time PTE pages aren't used after boot.
  78  * If you really want the space back, just remap it yourself.
  79  * boot_ioremap(&ioremap_space-PAGE_OFFSET, BOOT_IOREMAP_SIZE)
  80  */
  81 __init void* boot_ioremap(unsigned long phys_addr, unsigned long size)
  82 {
  83         unsigned long last_addr, offset;
  84         unsigned int nrpages;
  85
  86         last_addr = phys_addr + size - 1;
  87
  88         /* page align the requested address */
  89         offset = phys_addr & ~PAGE_MASK;
  90         phys_addr &= PAGE_MASK;
  91         size = PAGE_ALIGN(last_addr) - phys_addr;
  92
  93         nrpages = size >> PAGE_SHIFT;
  94         if (nrpages > BOOT_IOREMAP_PAGES)
  95                 return NULL;
  96
  97         __boot_ioremap(phys_addr, nrpages, boot_ioremap_space);
  98
  99         return &boot_ioremap_space[offset];
 100 }