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
34static unsigned long boot_pte_index(unsigned long vaddr)
35{
36	return __pa(vaddr) >> PAGE_SHIFT;
37}
38
39static 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 */
50static 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)
67static __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}
101