x86/xen: resume timer irqs early

[linux/fpc-iii.git] / arch / arm / mm / mmu.c

/*
 *  linux/arch/arm/mm/mmu.c
 *
 *  Copyright (C) 1995-2005 Russell King
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 */
#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/errno.h>
#include <linux/init.h>
#include <linux/mman.h>
#include <linux/nodemask.h>
#include <linux/memblock.h>
#include <linux/fs.h>
#include <linux/vmalloc.h>
#include <linux/sizes.h>

#include <asm/cp15.h>
#include <asm/cputype.h>
#include <asm/sections.h>
#include <asm/cachetype.h>
#include <asm/setup.h>
#include <asm/smp_plat.h>
#include <asm/tlb.h>
#include <asm/highmem.h>
#include <asm/system_info.h>
#include <asm/traps.h>

#include <asm/mach/arch.h>
#include <asm/mach/map.h>
#include <asm/mach/pci.h>

#include "mm.h"
#include "tcm.h"

/*
 * empty_zero_page is a special page that is used for
 * zero-initialized data and COW.
 */
struct page *empty_zero_page;
EXPORT_SYMBOL(empty_zero_page);

/*
 * The pmd table for the upper-most set of pages.
 */
pmd_t *top_pmd;

#define CPOLICY_UNCACHED        0
#define CPOLICY_BUFFERED        1
#define CPOLICY_WRITETHROUGH    2
#define CPOLICY_WRITEBACK       3
#define CPOLICY_WRITEALLOC      4

static unsigned int cachepolicy __initdata = CPOLICY_WRITEBACK;
static unsigned int ecc_mask __initdata = 0;
pgprot_t pgprot_user;
pgprot_t pgprot_kernel;
pgprot_t pgprot_hyp_device;
pgprot_t pgprot_s2;
pgprot_t pgprot_s2_device;

EXPORT_SYMBOL(pgprot_user);
EXPORT_SYMBOL(pgprot_kernel);

struct cachepolicy {
        const char      policy[16];
        unsigned int    cr_mask;
        pmdval_t        pmd;
        pteval_t        pte;
        pteval_t        pte_s2;
};

#ifdef CONFIG_ARM_LPAE
#define s2_policy(policy)       policy
#else
#define s2_policy(policy)       0
#endif

static struct cachepolicy cache_policies[] __initdata = {
        {
                .policy         = "uncached",
                .cr_mask        = CR_W|CR_C,
                .pmd            = PMD_SECT_UNCACHED,
                .pte            = L_PTE_MT_UNCACHED,
                .pte_s2         = s2_policy(L_PTE_S2_MT_UNCACHED),
        }, {
                .policy         = "buffered",
                .cr_mask        = CR_C,
                .pmd            = PMD_SECT_BUFFERED,
                .pte            = L_PTE_MT_BUFFERABLE,
                .pte_s2         = s2_policy(L_PTE_S2_MT_UNCACHED),
        }, {
                .policy         = "writethrough",
                .cr_mask        = 0,
                .pmd            = PMD_SECT_WT,
                .pte            = L_PTE_MT_WRITETHROUGH,
                .pte_s2         = s2_policy(L_PTE_S2_MT_WRITETHROUGH),
        }, {
                .policy         = "writeback",
                .cr_mask        = 0,
                .pmd            = PMD_SECT_WB,
                .pte            = L_PTE_MT_WRITEBACK,
                .pte_s2         = s2_policy(L_PTE_S2_MT_WRITEBACK),
        }, {
                .policy         = "writealloc",
                .cr_mask        = 0,
                .pmd            = PMD_SECT_WBWA,
                .pte            = L_PTE_MT_WRITEALLOC,
                .pte_s2         = s2_policy(L_PTE_S2_MT_WRITEBACK),
        }
};

#ifdef CONFIG_CPU_CP15
/*
 * These are useful for identifying cache coherency
 * problems by allowing the cache or the cache and
 * writebuffer to be turned off.  (Note: the write
 * buffer should not be on and the cache off).
 */
static int __init early_cachepolicy(char *p)
{
        int i;

        for (i = 0; i < ARRAY_SIZE(cache_policies); i++) {
                int len = strlen(cache_policies[i].policy);

                if (memcmp(p, cache_policies[i].policy, len) == 0) {
                        cachepolicy = i;
                        cr_alignment &= ~cache_policies[i].cr_mask;
                        cr_no_alignment &= ~cache_policies[i].cr_mask;
                        break;
                }
        }
        if (i == ARRAY_SIZE(cache_policies))
                printk(KERN_ERR "ERROR: unknown or unsupported cache policy\n");
        /*
         * This restriction is partly to do with the way we boot; it is
         * unpredictable to have memory mapped using two different sets of
         * memory attributes (shared, type, and cache attribs).  We can not
         * change these attributes once the initial assembly has setup the
         * page tables.
         */
        if (cpu_architecture() >= CPU_ARCH_ARMv6) {
                printk(KERN_WARNING "Only cachepolicy=writeback supported on ARMv6 and later\n");
                cachepolicy = CPOLICY_WRITEBACK;
        }
        flush_cache_all();
        set_cr(cr_alignment);
        return 0;
}
early_param("cachepolicy", early_cachepolicy);

static int __init early_nocache(char *__unused)
{
        char *p = "buffered";
        printk(KERN_WARNING "nocache is deprecated; use cachepolicy=%s\n", p);
        early_cachepolicy(p);
        return 0;
}
early_param("nocache", early_nocache);

static int __init early_nowrite(char *__unused)
{
        char *p = "uncached";
        printk(KERN_WARNING "nowb is deprecated; use cachepolicy=%s\n", p);
        early_cachepolicy(p);
        return 0;
}
early_param("nowb", early_nowrite);

#ifndef CONFIG_ARM_LPAE
static int __init early_ecc(char *p)
{
        if (memcmp(p, "on", 2) == 0)
                ecc_mask = PMD_PROTECTION;
        else if (memcmp(p, "off", 3) == 0)
                ecc_mask = 0;
        return 0;
}
early_param("ecc", early_ecc);
#endif

static int __init noalign_setup(char *__unused)
{
        cr_alignment &= ~CR_A;
        cr_no_alignment &= ~CR_A;
        set_cr(cr_alignment);
        return 1;
}
__setup("noalign", noalign_setup);

#ifndef CONFIG_SMP
void adjust_cr(unsigned long mask, unsigned long set)
{
        unsigned long flags;

        mask &= ~CR_A;

        set &= mask;

        local_irq_save(flags);

        cr_no_alignment = (cr_no_alignment & ~mask) | set;
        cr_alignment = (cr_alignment & ~mask) | set;

        set_cr((get_cr() & ~mask) | set);

        local_irq_restore(flags);
}
#endif

#else /* ifdef CONFIG_CPU_CP15 */

static int __init early_cachepolicy(char *p)
{
        pr_warning("cachepolicy kernel parameter not supported without cp15\n");
}
early_param("cachepolicy", early_cachepolicy);

static int __init noalign_setup(char *__unused)
{
        pr_warning("noalign kernel parameter not supported without cp15\n");
}
__setup("noalign", noalign_setup);

#endif /* ifdef CONFIG_CPU_CP15 / else */

#define PROT_PTE_DEVICE         L_PTE_PRESENT|L_PTE_YOUNG|L_PTE_DIRTY|L_PTE_XN
#define PROT_PTE_S2_DEVICE      PROT_PTE_DEVICE
#define PROT_SECT_DEVICE        PMD_TYPE_SECT|PMD_SECT_AP_WRITE

static struct mem_type mem_types[] = {
        [MT_DEVICE] = {           /* Strongly ordered / ARMv6 shared device */
                .prot_pte       = PROT_PTE_DEVICE | L_PTE_MT_DEV_SHARED |
                                  L_PTE_SHARED,
                .prot_pte_s2    = s2_policy(PROT_PTE_S2_DEVICE) |
                                  s2_policy(L_PTE_S2_MT_DEV_SHARED) |
                                  L_PTE_SHARED,
                .prot_l1        = PMD_TYPE_TABLE,
                .prot_sect      = PROT_SECT_DEVICE | PMD_SECT_S,
                .domain         = DOMAIN_IO,
        },
        [MT_DEVICE_NONSHARED] = { /* ARMv6 non-shared device */
                .prot_pte       = PROT_PTE_DEVICE | L_PTE_MT_DEV_NONSHARED,
                .prot_l1        = PMD_TYPE_TABLE,
                .prot_sect      = PROT_SECT_DEVICE,
                .domain         = DOMAIN_IO,
        },
        [MT_DEVICE_CACHED] = {    /* ioremap_cached */
                .prot_pte       = PROT_PTE_DEVICE | L_PTE_MT_DEV_CACHED,
                .prot_l1        = PMD_TYPE_TABLE,
                .prot_sect      = PROT_SECT_DEVICE | PMD_SECT_WB,
                .domain         = DOMAIN_IO,
        },
        [MT_DEVICE_WC] = {      /* ioremap_wc */
                .prot_pte       = PROT_PTE_DEVICE | L_PTE_MT_DEV_WC,
                .prot_l1        = PMD_TYPE_TABLE,
                .prot_sect      = PROT_SECT_DEVICE,
                .domain         = DOMAIN_IO,
        },
        [MT_UNCACHED] = {
                .prot_pte       = PROT_PTE_DEVICE,
                .prot_l1        = PMD_TYPE_TABLE,
                .prot_sect      = PMD_TYPE_SECT | PMD_SECT_XN,
                .domain         = DOMAIN_IO,
        },
        [MT_CACHECLEAN] = {
                .prot_sect = PMD_TYPE_SECT | PMD_SECT_XN,
                .domain    = DOMAIN_KERNEL,
        },
#ifndef CONFIG_ARM_LPAE
        [MT_MINICLEAN] = {
                .prot_sect = PMD_TYPE_SECT | PMD_SECT_XN | PMD_SECT_MINICACHE,
                .domain    = DOMAIN_KERNEL,
        },
#endif
        [MT_LOW_VECTORS] = {
                .prot_pte  = L_PTE_PRESENT | L_PTE_YOUNG | L_PTE_DIRTY |
                                L_PTE_RDONLY,
                .prot_l1   = PMD_TYPE_TABLE,
                .domain    = DOMAIN_USER,
        },
        [MT_HIGH_VECTORS] = {
                .prot_pte  = L_PTE_PRESENT | L_PTE_YOUNG | L_PTE_DIRTY |
                                L_PTE_USER | L_PTE_RDONLY,
                .prot_l1   = PMD_TYPE_TABLE,
                .domain    = DOMAIN_USER,
        },
        [MT_MEMORY] = {
                .prot_pte  = L_PTE_PRESENT | L_PTE_YOUNG | L_PTE_DIRTY,
                .prot_l1   = PMD_TYPE_TABLE,
                .prot_sect = PMD_TYPE_SECT | PMD_SECT_AP_WRITE,
                .domain    = DOMAIN_KERNEL,
        },
        [MT_ROM] = {
                .prot_sect = PMD_TYPE_SECT,
                .domain    = DOMAIN_KERNEL,
        },
        [MT_MEMORY_NONCACHED] = {
                .prot_pte  = L_PTE_PRESENT | L_PTE_YOUNG | L_PTE_DIRTY |
                                L_PTE_MT_BUFFERABLE,
                .prot_l1   = PMD_TYPE_TABLE,
                .prot_sect = PMD_TYPE_SECT | PMD_SECT_AP_WRITE,
                .domain    = DOMAIN_KERNEL,
        },
        [MT_MEMORY_DTCM] = {
                .prot_pte  = L_PTE_PRESENT | L_PTE_YOUNG | L_PTE_DIRTY |
                                L_PTE_XN,
                .prot_l1   = PMD_TYPE_TABLE,
                .prot_sect = PMD_TYPE_SECT | PMD_SECT_XN,
                .domain    = DOMAIN_KERNEL,
        },
        [MT_MEMORY_ITCM] = {
                .prot_pte  = L_PTE_PRESENT | L_PTE_YOUNG | L_PTE_DIRTY,
                .prot_l1   = PMD_TYPE_TABLE,
                .domain    = DOMAIN_KERNEL,
        },
        [MT_MEMORY_SO] = {
                .prot_pte  = L_PTE_PRESENT | L_PTE_YOUNG | L_PTE_DIRTY |
                                L_PTE_MT_UNCACHED | L_PTE_XN,
                .prot_l1   = PMD_TYPE_TABLE,
                .prot_sect = PMD_TYPE_SECT | PMD_SECT_AP_WRITE | PMD_SECT_S |
                                PMD_SECT_UNCACHED | PMD_SECT_XN,
                .domain    = DOMAIN_KERNEL,
        },
        [MT_MEMORY_DMA_READY] = {
                .prot_pte  = L_PTE_PRESENT | L_PTE_YOUNG | L_PTE_DIRTY,
                .prot_l1   = PMD_TYPE_TABLE,
                .domain    = DOMAIN_KERNEL,
        },
};

const struct mem_type *get_mem_type(unsigned int type)
{
        return type < ARRAY_SIZE(mem_types) ? &mem_types[type] : NULL;
}
EXPORT_SYMBOL(get_mem_type);

/*
 * Adjust the PMD section entries according to the CPU in use.
 */
static void __init build_mem_type_table(void)
{
        struct cachepolicy *cp;
        unsigned int cr = get_cr();
        pteval_t user_pgprot, kern_pgprot, vecs_pgprot;
        pteval_t hyp_device_pgprot, s2_pgprot, s2_device_pgprot;
        int cpu_arch = cpu_architecture();
        int i;

        if (cpu_arch < CPU_ARCH_ARMv6) {
#if defined(CONFIG_CPU_DCACHE_DISABLE)
                if (cachepolicy > CPOLICY_BUFFERED)
                        cachepolicy = CPOLICY_BUFFERED;
#elif defined(CONFIG_CPU_DCACHE_WRITETHROUGH)
                if (cachepolicy > CPOLICY_WRITETHROUGH)
                        cachepolicy = CPOLICY_WRITETHROUGH;
#endif
        }
        if (cpu_arch < CPU_ARCH_ARMv5) {
                if (cachepolicy >= CPOLICY_WRITEALLOC)
                        cachepolicy = CPOLICY_WRITEBACK;
                ecc_mask = 0;
        }
        if (is_smp())
                cachepolicy = CPOLICY_WRITEALLOC;

        /*
         * Strip out features not present on earlier architectures.
         * Pre-ARMv5 CPUs don't have TEX bits.  Pre-ARMv6 CPUs or those
         * without extended page tables don't have the 'Shared' bit.
         */
        if (cpu_arch < CPU_ARCH_ARMv5)
                for (i = 0; i < ARRAY_SIZE(mem_types); i++)
                        mem_types[i].prot_sect &= ~PMD_SECT_TEX(7);
        if ((cpu_arch < CPU_ARCH_ARMv6 || !(cr & CR_XP)) && !cpu_is_xsc3())
                for (i = 0; i < ARRAY_SIZE(mem_types); i++)
                        mem_types[i].prot_sect &= ~PMD_SECT_S;

        /*
         * ARMv5 and lower, bit 4 must be set for page tables (was: cache
         * "update-able on write" bit on ARM610).  However, Xscale and
         * Xscale3 require this bit to be cleared.
         */
        if (cpu_is_xscale() || cpu_is_xsc3()) {
                for (i = 0; i < ARRAY_SIZE(mem_types); i++) {
                        mem_types[i].prot_sect &= ~PMD_BIT4;
                        mem_types[i].prot_l1 &= ~PMD_BIT4;
                }
        } else if (cpu_arch < CPU_ARCH_ARMv6) {
                for (i = 0; i < ARRAY_SIZE(mem_types); i++) {
                        if (mem_types[i].prot_l1)
                                mem_types[i].prot_l1 |= PMD_BIT4;
                        if (mem_types[i].prot_sect)
                                mem_types[i].prot_sect |= PMD_BIT4;
                }
        }

        /*
         * Mark the device areas according to the CPU/architecture.
         */
        if (cpu_is_xsc3() || (cpu_arch >= CPU_ARCH_ARMv6 && (cr & CR_XP))) {
                if (!cpu_is_xsc3()) {
                        /*
                         * Mark device regions on ARMv6+ as execute-never
                         * to prevent speculative instruction fetches.
                         */
                        mem_types[MT_DEVICE].prot_sect |= PMD_SECT_XN;
                        mem_types[MT_DEVICE_NONSHARED].prot_sect |= PMD_SECT_XN;
                        mem_types[MT_DEVICE_CACHED].prot_sect |= PMD_SECT_XN;
                        mem_types[MT_DEVICE_WC].prot_sect |= PMD_SECT_XN;
                }
                if (cpu_arch >= CPU_ARCH_ARMv7 && (cr & CR_TRE)) {
                        /*
                         * For ARMv7 with TEX remapping,
                         * - shared device is SXCB=1100
                         * - nonshared device is SXCB=0100
                         * - write combine device mem is SXCB=0001
                         * (Uncached Normal memory)
                         */
                        mem_types[MT_DEVICE].prot_sect |= PMD_SECT_TEX(1);
                        mem_types[MT_DEVICE_NONSHARED].prot_sect |= PMD_SECT_TEX(1);
                        mem_types[MT_DEVICE_WC].prot_sect |= PMD_SECT_BUFFERABLE;
                } else if (cpu_is_xsc3()) {
                        /*
                         * For Xscale3,
                         * - shared device is TEXCB=00101
                         * - nonshared device is TEXCB=01000
                         * - write combine device mem is TEXCB=00100
                         * (Inner/Outer Uncacheable in xsc3 parlance)
                         */
                        mem_types[MT_DEVICE].prot_sect |= PMD_SECT_TEX(1) | PMD_SECT_BUFFERED;
                        mem_types[MT_DEVICE_NONSHARED].prot_sect |= PMD_SECT_TEX(2);
                        mem_types[MT_DEVICE_WC].prot_sect |= PMD_SECT_TEX(1);
                } else {
                        /*
                         * For ARMv6 and ARMv7 without TEX remapping,
                         * - shared device is TEXCB=00001
                         * - nonshared device is TEXCB=01000
                         * - write combine device mem is TEXCB=00100
                         * (Uncached Normal in ARMv6 parlance).
                         */
                        mem_types[MT_DEVICE].prot_sect |= PMD_SECT_BUFFERED;
                        mem_types[MT_DEVICE_NONSHARED].prot_sect |= PMD_SECT_TEX(2);
                        mem_types[MT_DEVICE_WC].prot_sect |= PMD_SECT_TEX(1);
                }
        } else {
                /*
                 * On others, write combining is "Uncached/Buffered"
                 */
                mem_types[MT_DEVICE_WC].prot_sect |= PMD_SECT_BUFFERABLE;
        }

        /*
         * Now deal with the memory-type mappings
         */
        cp = &cache_policies[cachepolicy];
        vecs_pgprot = kern_pgprot = user_pgprot = cp->pte;
        s2_pgprot = cp->pte_s2;
        hyp_device_pgprot = mem_types[MT_DEVICE].prot_pte;
        s2_device_pgprot = mem_types[MT_DEVICE].prot_pte_s2;

        /*
         * We don't use domains on ARMv6 (since this causes problems with
         * v6/v7 kernels), so we must use a separate memory type for user
         * r/o, kernel r/w to map the vectors page.
         */
#ifndef CONFIG_ARM_LPAE
        if (cpu_arch == CPU_ARCH_ARMv6)
                vecs_pgprot |= L_PTE_MT_VECTORS;
#endif

        /*
         * ARMv6 and above have extended page tables.
         */
        if (cpu_arch >= CPU_ARCH_ARMv6 && (cr & CR_XP)) {
#ifndef CONFIG_ARM_LPAE
                /*
                 * Mark cache clean areas and XIP ROM read only
                 * from SVC mode and no access from userspace.
                 */
                mem_types[MT_ROM].prot_sect |= PMD_SECT_APX|PMD_SECT_AP_WRITE;
                mem_types[MT_MINICLEAN].prot_sect |= PMD_SECT_APX|PMD_SECT_AP_WRITE;
                mem_types[MT_CACHECLEAN].prot_sect |= PMD_SECT_APX|PMD_SECT_AP_WRITE;
#endif

                if (is_smp()) {
                        /*
                         * Mark memory with the "shared" attribute
                         * for SMP systems
                         */
                        user_pgprot |= L_PTE_SHARED;
                        kern_pgprot |= L_PTE_SHARED;
                        vecs_pgprot |= L_PTE_SHARED;
                        s2_pgprot |= L_PTE_SHARED;
                        mem_types[MT_DEVICE_WC].prot_sect |= PMD_SECT_S;
                        mem_types[MT_DEVICE_WC].prot_pte |= L_PTE_SHARED;
                        mem_types[MT_DEVICE_CACHED].prot_sect |= PMD_SECT_S;
                        mem_types[MT_DEVICE_CACHED].prot_pte |= L_PTE_SHARED;
                        mem_types[MT_MEMORY].prot_sect |= PMD_SECT_S;
                        mem_types[MT_MEMORY].prot_pte |= L_PTE_SHARED;
                        mem_types[MT_MEMORY_DMA_READY].prot_pte |= L_PTE_SHARED;
                        mem_types[MT_MEMORY_NONCACHED].prot_sect |= PMD_SECT_S;
                        mem_types[MT_MEMORY_NONCACHED].prot_pte |= L_PTE_SHARED;
                }
        }

        /*
         * Non-cacheable Normal - intended for memory areas that must
         * not cause dirty cache line writebacks when used
         */
        if (cpu_arch >= CPU_ARCH_ARMv6) {
                if (cpu_arch >= CPU_ARCH_ARMv7 && (cr & CR_TRE)) {
                        /* Non-cacheable Normal is XCB = 001 */
                        mem_types[MT_MEMORY_NONCACHED].prot_sect |=
                                PMD_SECT_BUFFERED;
                } else {
                        /* For both ARMv6 and non-TEX-remapping ARMv7 */
                        mem_types[MT_MEMORY_NONCACHED].prot_sect |=
                                PMD_SECT_TEX(1);
                }
        } else {
                mem_types[MT_MEMORY_NONCACHED].prot_sect |= PMD_SECT_BUFFERABLE;
        }

#ifdef CONFIG_ARM_LPAE
        /*
         * Do not generate access flag faults for the kernel mappings.
         */
        for (i = 0; i < ARRAY_SIZE(mem_types); i++) {
                mem_types[i].prot_pte |= PTE_EXT_AF;
                if (mem_types[i].prot_sect)
                        mem_types[i].prot_sect |= PMD_SECT_AF;
        }
        kern_pgprot |= PTE_EXT_AF;
        vecs_pgprot |= PTE_EXT_AF;
#endif

        for (i = 0; i < 16; i++) {
                pteval_t v = pgprot_val(protection_map[i]);
                protection_map[i] = __pgprot(v | user_pgprot);
        }

        mem_types[MT_LOW_VECTORS].prot_pte |= vecs_pgprot;
        mem_types[MT_HIGH_VECTORS].prot_pte |= vecs_pgprot;

        pgprot_user   = __pgprot(L_PTE_PRESENT | L_PTE_YOUNG | user_pgprot);
        pgprot_kernel = __pgprot(L_PTE_PRESENT | L_PTE_YOUNG |
                                 L_PTE_DIRTY | kern_pgprot);
        pgprot_s2  = __pgprot(L_PTE_PRESENT | L_PTE_YOUNG | s2_pgprot);
        pgprot_s2_device  = __pgprot(s2_device_pgprot);
        pgprot_hyp_device  = __pgprot(hyp_device_pgprot);

        mem_types[MT_LOW_VECTORS].prot_l1 |= ecc_mask;
        mem_types[MT_HIGH_VECTORS].prot_l1 |= ecc_mask;
        mem_types[MT_MEMORY].prot_sect |= ecc_mask | cp->pmd;
        mem_types[MT_MEMORY].prot_pte |= kern_pgprot;
        mem_types[MT_MEMORY_DMA_READY].prot_pte |= kern_pgprot;
        mem_types[MT_MEMORY_NONCACHED].prot_sect |= ecc_mask;
        mem_types[MT_ROM].prot_sect |= cp->pmd;

        switch (cp->pmd) {
        case PMD_SECT_WT:
                mem_types[MT_CACHECLEAN].prot_sect |= PMD_SECT_WT;
                break;
        case PMD_SECT_WB:
        case PMD_SECT_WBWA:
                mem_types[MT_CACHECLEAN].prot_sect |= PMD_SECT_WB;
                break;
        }
        printk("Memory policy: ECC %sabled, Data cache %s\n",
                ecc_mask ? "en" : "dis", cp->policy);

        for (i = 0; i < ARRAY_SIZE(mem_types); i++) {
                struct mem_type *t = &mem_types[i];
                if (t->prot_l1)
                        t->prot_l1 |= PMD_DOMAIN(t->domain);
                if (t->prot_sect)
                        t->prot_sect |= PMD_DOMAIN(t->domain);
        }
}

#ifdef CONFIG_ARM_DMA_MEM_BUFFERABLE
pgprot_t phys_mem_access_prot(struct file *file, unsigned long pfn,
                              unsigned long size, pgprot_t vma_prot)
{
        if (!pfn_valid(pfn))
                return pgprot_noncached(vma_prot);
        else if (file->f_flags & O_SYNC)
                return pgprot_writecombine(vma_prot);
        return vma_prot;
}
EXPORT_SYMBOL(phys_mem_access_prot);
#endif

#define vectors_base()  (vectors_high() ? 0xffff0000 : 0)

static void __init *early_alloc_aligned(unsigned long sz, unsigned long align)
{
        void *ptr = __va(memblock_alloc(sz, align));
        memset(ptr, 0, sz);
        return ptr;
}

static void __init *early_alloc(unsigned long sz)
{
        return early_alloc_aligned(sz, sz);
}

static pte_t * __init early_pte_alloc(pmd_t *pmd, unsigned long addr, unsigned long prot)
{
        if (pmd_none(*pmd)) {
                pte_t *pte = early_alloc(PTE_HWTABLE_OFF + PTE_HWTABLE_SIZE);
                __pmd_populate(pmd, __pa(pte), prot);
        }
        BUG_ON(pmd_bad(*pmd));
        return pte_offset_kernel(pmd, addr);
}

static void __init alloc_init_pte(pmd_t *pmd, unsigned long addr,
                                  unsigned long end, unsigned long pfn,
                                  const struct mem_type *type)
{
        pte_t *pte = early_pte_alloc(pmd, addr, type->prot_l1);
        do {
                set_pte_ext(pte, pfn_pte(pfn, __pgprot(type->prot_pte)), 0);
                pfn++;
        } while (pte++, addr += PAGE_SIZE, addr != end);
}

static void __init __map_init_section(pmd_t *pmd, unsigned long addr,
                        unsigned long end, phys_addr_t phys,
                        const struct mem_type *type)
{
        pmd_t *p = pmd;

#ifndef CONFIG_ARM_LPAE
        /*
         * In classic MMU format, puds and pmds are folded in to
         * the pgds. pmd_offset gives the PGD entry. PGDs refer to a
         * group of L1 entries making up one logical pointer to
         * an L2 table (2MB), where as PMDs refer to the individual
         * L1 entries (1MB). Hence increment to get the correct
         * offset for odd 1MB sections.
         * (See arch/arm/include/asm/pgtable-2level.h)
         */
        if (addr & SECTION_SIZE)
                pmd++;
#endif
        do {
                *pmd = __pmd(phys | type->prot_sect);
                phys += SECTION_SIZE;
        } while (pmd++, addr += SECTION_SIZE, addr != end);

        flush_pmd_entry(p);
}

static void __init alloc_init_pmd(pud_t *pud, unsigned long addr,
                                      unsigned long end, phys_addr_t phys,
                                      const struct mem_type *type)
{
        pmd_t *pmd = pmd_offset(pud, addr);
        unsigned long next;

        do {
                /*
                 * With LPAE, we must loop over to map
                 * all the pmds for the given range.
                 */
                next = pmd_addr_end(addr, end);

                /*
                 * Try a section mapping - addr, next and phys must all be
                 * aligned to a section boundary.
                 */
                if (type->prot_sect &&
                                ((addr | next | phys) & ~SECTION_MASK) == 0) {
                        __map_init_section(pmd, addr, next, phys, type);
                } else {
                        alloc_init_pte(pmd, addr, next,
                                                __phys_to_pfn(phys), type);
                }

                phys += next - addr;

        } while (pmd++, addr = next, addr != end);
}

static void __init alloc_init_pud(pgd_t *pgd, unsigned long addr,
                                  unsigned long end, phys_addr_t phys,
                                  const struct mem_type *type)
{
        pud_t *pud = pud_offset(pgd, addr);
        unsigned long next;

        do {
                next = pud_addr_end(addr, end);
                alloc_init_pmd(pud, addr, next, phys, type);
                phys += next - addr;
        } while (pud++, addr = next, addr != end);
}

#ifndef CONFIG_ARM_LPAE
static void __init create_36bit_mapping(struct map_desc *md,
                                        const struct mem_type *type)
{
        unsigned long addr, length, end;
        phys_addr_t phys;
        pgd_t *pgd;

        addr = md->virtual;
        phys = __pfn_to_phys(md->pfn);
        length = PAGE_ALIGN(md->length);

        if (!(cpu_architecture() >= CPU_ARCH_ARMv6 || cpu_is_xsc3())) {
                printk(KERN_ERR "MM: CPU does not support supersection "
                       "mapping for 0x%08llx at 0x%08lx\n",
                       (long long)__pfn_to_phys((u64)md->pfn), addr);
                return;
        }

        /* N.B. ARMv6 supersections are only defined to work with domain 0.
         *      Since domain assignments can in fact be arbitrary, the
         *      'domain == 0' check below is required to insure that ARMv6
         *      supersections are only allocated for domain 0 regardless
         *      of the actual domain assignments in use.
         */
        if (type->domain) {
                printk(KERN_ERR "MM: invalid domain in supersection "
                       "mapping for 0x%08llx at 0x%08lx\n",
                       (long long)__pfn_to_phys((u64)md->pfn), addr);
                return;
        }

        if ((addr | length | __pfn_to_phys(md->pfn)) & ~SUPERSECTION_MASK) {
                printk(KERN_ERR "MM: cannot create mapping for 0x%08llx"
                       " at 0x%08lx invalid alignment\n",
                       (long long)__pfn_to_phys((u64)md->pfn), addr);
                return;
        }

        /*
         * Shift bits [35:32] of address into bits [23:20] of PMD
         * (See ARMv6 spec).
         */
        phys |= (((md->pfn >> (32 - PAGE_SHIFT)) & 0xF) << 20);

        pgd = pgd_offset_k(addr);
        end = addr + length;
        do {
                pud_t *pud = pud_offset(pgd, addr);
                pmd_t *pmd = pmd_offset(pud, addr);
                int i;

                for (i = 0; i < 16; i++)
                        *pmd++ = __pmd(phys | type->prot_sect | PMD_SECT_SUPER);

                addr += SUPERSECTION_SIZE;
                phys += SUPERSECTION_SIZE;
                pgd += SUPERSECTION_SIZE >> PGDIR_SHIFT;
        } while (addr != end);
}
#endif  /* !CONFIG_ARM_LPAE */

/*
 * Create the page directory entries and any necessary
 * page tables for the mapping specified by `md'.  We
 * are able to cope here with varying sizes and address
 * offsets, and we take full advantage of sections and
 * supersections.
 */
static void __init create_mapping(struct map_desc *md)
{
        unsigned long addr, length, end;
        phys_addr_t phys;
        const struct mem_type *type;
        pgd_t *pgd;

        if (md->virtual != vectors_base() && md->virtual < TASK_SIZE) {
                printk(KERN_WARNING "BUG: not creating mapping for 0x%08llx"
                       " at 0x%08lx in user region\n",
                       (long long)__pfn_to_phys((u64)md->pfn), md->virtual);
                return;
        }

        if ((md->type == MT_DEVICE || md->type == MT_ROM) &&
            md->virtual >= PAGE_OFFSET &&
            (md->virtual < VMALLOC_START || md->virtual >= VMALLOC_END)) {
                printk(KERN_WARNING "BUG: mapping for 0x%08llx"
                       " at 0x%08lx out of vmalloc space\n",
                       (long long)__pfn_to_phys((u64)md->pfn), md->virtual);
        }

        type = &mem_types[md->type];

#ifndef CONFIG_ARM_LPAE
        /*
         * Catch 36-bit addresses
         */
        if (md->pfn >= 0x100000) {
                create_36bit_mapping(md, type);
                return;
        }
#endif

        addr = md->virtual & PAGE_MASK;
        phys = __pfn_to_phys(md->pfn);
        length = PAGE_ALIGN(md->length + (md->virtual & ~PAGE_MASK));

        if (type->prot_l1 == 0 && ((addr | phys | length) & ~SECTION_MASK)) {
                printk(KERN_WARNING "BUG: map for 0x%08llx at 0x%08lx can not "
                       "be mapped using pages, ignoring.\n",
                       (long long)__pfn_to_phys(md->pfn), addr);
                return;
        }

        pgd = pgd_offset_k(addr);
        end = addr + length;
        do {
                unsigned long next = pgd_addr_end(addr, end);

                alloc_init_pud(pgd, addr, next, phys, type);

                phys += next - addr;
                addr = next;
        } while (pgd++, addr != end);
}

/*
 * Create the architecture specific mappings
 */
void __init iotable_init(struct map_desc *io_desc, int nr)
{
        struct map_desc *md;
        struct vm_struct *vm;
        struct static_vm *svm;

        if (!nr)
                return;

        svm = early_alloc_aligned(sizeof(*svm) * nr, __alignof__(*svm));

        for (md = io_desc; nr; md++, nr--) {
                create_mapping(md);

                vm = &svm->vm;
                vm->addr = (void *)(md->virtual & PAGE_MASK);
                vm->size = PAGE_ALIGN(md->length + (md->virtual & ~PAGE_MASK));
                vm->phys_addr = __pfn_to_phys(md->pfn);
                vm->flags = VM_IOREMAP | VM_ARM_STATIC_MAPPING;
                vm->flags |= VM_ARM_MTYPE(md->type);
                vm->caller = iotable_init;
                add_static_vm_early(svm++);
        }
}

void __init vm_reserve_area_early(unsigned long addr, unsigned long size,
                                  void *caller)
{
        struct vm_struct *vm;
        struct static_vm *svm;

        svm = early_alloc_aligned(sizeof(*svm), __alignof__(*svm));

        vm = &svm->vm;
        vm->addr = (void *)addr;
        vm->size = size;
        vm->flags = VM_IOREMAP | VM_ARM_EMPTY_MAPPING;
        vm->caller = caller;
        add_static_vm_early(svm);
}

#ifndef CONFIG_ARM_LPAE

/*
 * The Linux PMD is made of two consecutive section entries covering 2MB
 * (see definition in include/asm/pgtable-2level.h).  However a call to
 * create_mapping() may optimize static mappings by using individual
 * 1MB section mappings.  This leaves the actual PMD potentially half
 * initialized if the top or bottom section entry isn't used, leaving it
 * open to problems if a subsequent ioremap() or vmalloc() tries to use
 * the virtual space left free by that unused section entry.
 *
 * Let's avoid the issue by inserting dummy vm entries covering the unused
 * PMD halves once the static mappings are in place.
 */

static void __init pmd_empty_section_gap(unsigned long addr)
{
        vm_reserve_area_early(addr, SECTION_SIZE, pmd_empty_section_gap);
}

static void __init fill_pmd_gaps(void)
{
        struct static_vm *svm;
        struct vm_struct *vm;
        unsigned long addr, next = 0;
        pmd_t *pmd;

        list_for_each_entry(svm, &static_vmlist, list) {
                vm = &svm->vm;
                addr = (unsigned long)vm->addr;
                if (addr < next)
                        continue;

                /*
                 * Check if this vm starts on an odd section boundary.
                 * If so and the first section entry for this PMD is free
                 * then we block the corresponding virtual address.
                 */
                if ((addr & ~PMD_MASK) == SECTION_SIZE) {
                        pmd = pmd_off_k(addr);
                        if (pmd_none(*pmd))
                                pmd_empty_section_gap(addr & PMD_MASK);
                }

                /*
                 * Then check if this vm ends on an odd section boundary.
                 * If so and the second section entry for this PMD is empty
                 * then we block the corresponding virtual address.
                 */
                addr += vm->size;
                if ((addr & ~PMD_MASK) == SECTION_SIZE) {
                        pmd = pmd_off_k(addr) + 1;
                        if (pmd_none(*pmd))
                                pmd_empty_section_gap(addr);
                }

                /* no need to look at any vm entry until we hit the next PMD */
                next = (addr + PMD_SIZE - 1) & PMD_MASK;
        }
}

#else
#define fill_pmd_gaps() do { } while (0)
#endif

#if defined(CONFIG_PCI) && !defined(CONFIG_NEED_MACH_IO_H)
static void __init pci_reserve_io(void)
{
        struct static_vm *svm;

        svm = find_static_vm_vaddr((void *)PCI_IO_VIRT_BASE);
        if (svm)
                return;

        vm_reserve_area_early(PCI_IO_VIRT_BASE, SZ_2M, pci_reserve_io);
}
#else
#define pci_reserve_io() do { } while (0)
#endif

#ifdef CONFIG_DEBUG_LL
void __init debug_ll_io_init(void)
{
        struct map_desc map;

        debug_ll_addr(&map.pfn, &map.virtual);
        if (!map.pfn || !map.virtual)
                return;
        map.pfn = __phys_to_pfn(map.pfn);
        map.virtual &= PAGE_MASK;
        map.length = PAGE_SIZE;
        map.type = MT_DEVICE;
        iotable_init(&map, 1);
}
#endif

static void * __initdata vmalloc_min =
        (void *)(VMALLOC_END - (240 << 20) - VMALLOC_OFFSET);

/*
 * vmalloc=size forces the vmalloc area to be exactly 'size'
 * bytes. This can be used to increase (or decrease) the vmalloc
 * area - the default is 240m.
 */
static int __init early_vmalloc(char *arg)
{
        unsigned long vmalloc_reserve = memparse(arg, NULL);

        if (vmalloc_reserve < SZ_16M) {
                vmalloc_reserve = SZ_16M;
                printk(KERN_WARNING
                        "vmalloc area too small, limiting to %luMB\n",
                        vmalloc_reserve >> 20);
        }

        if (vmalloc_reserve > VMALLOC_END - (PAGE_OFFSET + SZ_32M)) {
                vmalloc_reserve = VMALLOC_END - (PAGE_OFFSET + SZ_32M);
                printk(KERN_WARNING
                        "vmalloc area is too big, limiting to %luMB\n",
                        vmalloc_reserve >> 20);
        }

        vmalloc_min = (void *)(VMALLOC_END - vmalloc_reserve);
        return 0;
}
early_param("vmalloc", early_vmalloc);

phys_addr_t arm_lowmem_limit __initdata = 0;

void __init sanity_check_meminfo(void)
{
        phys_addr_t memblock_limit = 0;
        int i, j, highmem = 0;
        phys_addr_t vmalloc_limit = __pa(vmalloc_min - 1) + 1;

        for (i = 0, j = 0; i < meminfo.nr_banks; i++) {
                struct membank *bank = &meminfo.bank[j];
                phys_addr_t size_limit;

                *bank = meminfo.bank[i];
                size_limit = bank->size;

                if (bank->start >= vmalloc_limit)
                        highmem = 1;
                else
                        size_limit = vmalloc_limit - bank->start;

                bank->highmem = highmem;

#ifdef CONFIG_HIGHMEM
                /*
                 * Split those memory banks which are partially overlapping
                 * the vmalloc area greatly simplifying things later.
                 */
                if (!highmem && bank->size > size_limit) {
                        if (meminfo.nr_banks >= NR_BANKS) {
                                printk(KERN_CRIT "NR_BANKS too low, "
                                                 "ignoring high memory\n");
                        } else {
                                memmove(bank + 1, bank,
                                        (meminfo.nr_banks - i) * sizeof(*bank));
                                meminfo.nr_banks++;
                                i++;
                                bank[1].size -= size_limit;
                                bank[1].start = vmalloc_limit;
                                bank[1].highmem = highmem = 1;
                                j++;
                        }
                        bank->size = size_limit;
                }
#else
                /*
                 * Highmem banks not allowed with !CONFIG_HIGHMEM.
                 */
                if (highmem) {
                        printk(KERN_NOTICE "Ignoring RAM at %.8llx-%.8llx "
                               "(!CONFIG_HIGHMEM).\n",
                               (unsigned long long)bank->start,
                               (unsigned long long)bank->start + bank->size - 1);
                        continue;
                }

                /*
                 * Check whether this memory bank would partially overlap
                 * the vmalloc area.
                 */
                if (bank->size > size_limit) {
                        printk(KERN_NOTICE "Truncating RAM at %.8llx-%.8llx "
                               "to -%.8llx (vmalloc region overlap).\n",
                               (unsigned long long)bank->start,
                               (unsigned long long)bank->start + bank->size - 1,
                               (unsigned long long)bank->start + size_limit - 1);
                        bank->size = size_limit;
                }
#endif
                if (!bank->highmem) {
                        phys_addr_t bank_end = bank->start + bank->size;

                        if (bank_end > arm_lowmem_limit)
                                arm_lowmem_limit = bank_end;

                        /*
                         * Find the first non-section-aligned page, and point
                         * memblock_limit at it. This relies on rounding the
                         * limit down to be section-aligned, which happens at
                         * the end of this function.
                         *
                         * With this algorithm, the start or end of almost any
                         * bank can be non-section-aligned. The only exception
                         * is that the start of the bank 0 must be section-
                         * aligned, since otherwise memory would need to be
                         * allocated when mapping the start of bank 0, which
                         * occurs before any free memory is mapped.
                         */
                        if (!memblock_limit) {
                                if (!IS_ALIGNED(bank->start, SECTION_SIZE))
                                        memblock_limit = bank->start;
                                else if (!IS_ALIGNED(bank_end, SECTION_SIZE))
                                        memblock_limit = bank_end;
                        }
                }
                j++;
        }
#ifdef CONFIG_HIGHMEM
        if (highmem) {
                const char *reason = NULL;

                if (cache_is_vipt_aliasing()) {
                        /*
                         * Interactions between kmap and other mappings
                         * make highmem support with aliasing VIPT caches
                         * rather difficult.
                         */
                        reason = "with VIPT aliasing cache";
                }
                if (reason) {
                        printk(KERN_CRIT "HIGHMEM is not supported %s, ignoring high memory\n",
                                reason);
                        while (j > 0 && meminfo.bank[j - 1].highmem)
                                j--;
                }
        }
#endif
        meminfo.nr_banks = j;
        high_memory = __va(arm_lowmem_limit - 1) + 1;

        /*
         * Round the memblock limit down to a section size.  This
         * helps to ensure that we will allocate memory from the
         * last full section, which should be mapped.
         */
        if (memblock_limit)
                memblock_limit = round_down(memblock_limit, SECTION_SIZE);
        if (!memblock_limit)
                memblock_limit = arm_lowmem_limit;

        memblock_set_current_limit(memblock_limit);
}

static inline void prepare_page_table(void)
{
        unsigned long addr;
        phys_addr_t end;

        /*
         * Clear out all the mappings below the kernel image.
         */
        for (addr = 0; addr < MODULES_VADDR; addr += PMD_SIZE)
                pmd_clear(pmd_off_k(addr));

#ifdef CONFIG_XIP_KERNEL
        /* The XIP kernel is mapped in the module area -- skip over it */
        addr = ((unsigned long)_etext + PMD_SIZE - 1) & PMD_MASK;
#endif
        for ( ; addr < PAGE_OFFSET; addr += PMD_SIZE)
                pmd_clear(pmd_off_k(addr));

        /*
         * Find the end of the first block of lowmem.
         */
        end = memblock.memory.regions[0].base + memblock.memory.regions[0].size;
        if (end >= arm_lowmem_limit)
                end = arm_lowmem_limit;

        /*
         * Clear out all the kernel space mappings, except for the first
         * memory bank, up to the vmalloc region.
         */
        for (addr = __phys_to_virt(end);
             addr < VMALLOC_START; addr += PMD_SIZE)
                pmd_clear(pmd_off_k(addr));
}

#ifdef CONFIG_ARM_LPAE
/* the first page is reserved for pgd */
#define SWAPPER_PG_DIR_SIZE     (PAGE_SIZE + \
                                 PTRS_PER_PGD * PTRS_PER_PMD * sizeof(pmd_t))
#else
#define SWAPPER_PG_DIR_SIZE     (PTRS_PER_PGD * sizeof(pgd_t))
#endif

/*
 * Reserve the special regions of memory
 */
void __init arm_mm_memblock_reserve(void)
{
        /*
         * Reserve the page tables.  These are already in use,
         * and can only be in node 0.
         */
        memblock_reserve(__pa(swapper_pg_dir), SWAPPER_PG_DIR_SIZE);

#ifdef CONFIG_SA1111
        /*
         * Because of the SA1111 DMA bug, we want to preserve our
         * precious DMA-able memory...
         */
        memblock_reserve(PHYS_OFFSET, __pa(swapper_pg_dir) - PHYS_OFFSET);
#endif
}

/*
 * Set up the device mappings.  Since we clear out the page tables for all
 * mappings above VMALLOC_START, we will remove any debug device mappings.
 * This means you have to be careful how you debug this function, or any
 * called function.  This means you can't use any function or debugging
 * method which may touch any device, otherwise the kernel _will_ crash.
 */
static void __init devicemaps_init(const struct machine_desc *mdesc)
{
        struct map_desc map;
        unsigned long addr;
        void *vectors;

        /*
         * Allocate the vector page early.
         */
        vectors = early_alloc(PAGE_SIZE * 2);

        early_trap_init(vectors);

        for (addr = VMALLOC_START; addr; addr += PMD_SIZE)
                pmd_clear(pmd_off_k(addr));

        /*
         * Map the kernel if it is XIP.
         * It is always first in the modulearea.
         */
#ifdef CONFIG_XIP_KERNEL
        map.pfn = __phys_to_pfn(CONFIG_XIP_PHYS_ADDR & SECTION_MASK);
        map.virtual = MODULES_VADDR;
        map.length = ((unsigned long)_etext - map.virtual + ~SECTION_MASK) & SECTION_MASK;
        map.type = MT_ROM;
        create_mapping(&map);
#endif

        /*
         * Map the cache flushing regions.
         */
#ifdef FLUSH_BASE
        map.pfn = __phys_to_pfn(FLUSH_BASE_PHYS);
        map.virtual = FLUSH_BASE;
        map.length = SZ_1M;
        map.type = MT_CACHECLEAN;
        create_mapping(&map);
#endif
#ifdef FLUSH_BASE_MINICACHE
        map.pfn = __phys_to_pfn(FLUSH_BASE_PHYS + SZ_1M);
        map.virtual = FLUSH_BASE_MINICACHE;
        map.length = SZ_1M;
        map.type = MT_MINICLEAN;
        create_mapping(&map);
#endif

        /*
         * Create a mapping for the machine vectors at the high-vectors
         * location (0xffff0000).  If we aren't using high-vectors, also
         * create a mapping at the low-vectors virtual address.
         */
        map.pfn = __phys_to_pfn(virt_to_phys(vectors));
        map.virtual = 0xffff0000;
        map.length = PAGE_SIZE;
#ifdef CONFIG_KUSER_HELPERS
        map.type = MT_HIGH_VECTORS;
#else
        map.type = MT_LOW_VECTORS;
#endif
        create_mapping(&map);

        if (!vectors_high()) {
                map.virtual = 0;
                map.length = PAGE_SIZE * 2;
                map.type = MT_LOW_VECTORS;
                create_mapping(&map);
        }

        /* Now create a kernel read-only mapping */
        map.pfn += 1;
        map.virtual = 0xffff0000 + PAGE_SIZE;
        map.length = PAGE_SIZE;
        map.type = MT_LOW_VECTORS;
        create_mapping(&map);

        /*
         * Ask the machine support to map in the statically mapped devices.
         */
        if (mdesc->map_io)
                mdesc->map_io();
        else
                debug_ll_io_init();
        fill_pmd_gaps();

        /* Reserve fixed i/o space in VMALLOC region */
        pci_reserve_io();

        /*
         * Finally flush the caches and tlb to ensure that we're in a
         * consistent state wrt the writebuffer.  This also ensures that
         * any write-allocated cache lines in the vector page are written
         * back.  After this point, we can start to touch devices again.
         */
        local_flush_tlb_all();
        flush_cache_all();
}

static void __init kmap_init(void)
{
#ifdef CONFIG_HIGHMEM
        pkmap_page_table = early_pte_alloc(pmd_off_k(PKMAP_BASE),
                PKMAP_BASE, _PAGE_KERNEL_TABLE);
#endif
}

static void __init map_lowmem(void)
{
        struct memblock_region *reg;

        /* Map all the lowmem memory banks. */
        for_each_memblock(memory, reg) {
                phys_addr_t start = reg->base;
                phys_addr_t end = start + reg->size;
                struct map_desc map;

                if (end > arm_lowmem_limit)
                        end = arm_lowmem_limit;
                if (start >= end)
                        break;

                map.pfn = __phys_to_pfn(start);
                map.virtual = __phys_to_virt(start);
                map.length = end - start;
                map.type = MT_MEMORY;

                create_mapping(&map);
        }
}

/*
 * paging_init() sets up the page tables, initialises the zone memory
 * maps, and sets up the zero page, bad page and bad page tables.
 */
void __init paging_init(const struct machine_desc *mdesc)
{
        void *zero_page;

        build_mem_type_table();
        prepare_page_table();
        map_lowmem();
        dma_contiguous_remap();
        devicemaps_init(mdesc);
        kmap_init();
        tcm_init();

        top_pmd = pmd_off_k(0xffff0000);

        /* allocate the zero page. */
        zero_page = early_alloc(PAGE_SIZE);

        bootmem_init();

        empty_zero_page = virt_to_page(zero_page);
        __flush_dcache_page(NULL, empty_zero_page);
}