arch/arm/mm/highmem.c

/*
 * arch/arm/mm/highmem.c -- ARM highmem support
 *
 * Author:	Nicolas Pitre
 * Created:	september 8, 2008
 * Copyright:	Marvell Semiconductors Inc.
 *
 * 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/cpu.h>
#include <linux/module.h>
#include <linux/highmem.h>
#include <linux/interrupt.h>
#include <asm/fixmap.h>
#include <asm/cacheflush.h>
#include <asm/tlbflush.h>
#include "mm.h"

void *kmap(struct page *page)
{
	might_sleep();
	if (!PageHighMem(page))
		return page_address(page);
	return kmap_high(page);
}
EXPORT_SYMBOL(kmap);

void kunmap(struct page *page)
{
	BUG_ON(in_interrupt());
	if (!PageHighMem(page))
		return;
	kunmap_high(page);
}
EXPORT_SYMBOL(kunmap);

void *kmap_atomic(struct page *page)
{
	unsigned int idx;
	unsigned long vaddr;
	void *kmap;
	int type;

	pagefault_disable();
	if (!PageHighMem(page))
		return page_address(page);

#ifdef CONFIG_DEBUG_HIGHMEM
	/*
	 * There is no cache coherency issue when non VIVT, so force the
	 * dedicated kmap usage for better debugging purposes in that case.
	 */
	if (!cache_is_vivt())
		kmap = NULL;
	else
#endif
		kmap = kmap_high_get(page);
	if (kmap)
		return kmap;

	type = kmap_atomic_idx_push();

	idx = type + KM_TYPE_NR * smp_processor_id();
	vaddr = __fix_to_virt(FIX_KMAP_BEGIN + idx);
#ifdef CONFIG_DEBUG_HIGHMEM
	/*
	 * With debugging enabled, kunmap_atomic forces that entry to 0.
	 * Make sure it was indeed properly unmapped.
	 */
	BUG_ON(!pte_none(get_top_pte(vaddr)));
#endif
	/*
	 * When debugging is off, kunmap_atomic leaves the previous mapping
	 * in place, so the contained TLB flush ensures the TLB is updated
	 * with the new mapping.
	 */
	set_top_pte(vaddr, mk_pte(page, kmap_prot));

	return (void *)vaddr;
}
EXPORT_SYMBOL(kmap_atomic);

void __kunmap_atomic(void *kvaddr)
{
	unsigned long vaddr = (unsigned long) kvaddr & PAGE_MASK;
	int idx, type;

	if (kvaddr >= (void *)FIXADDR_START) {
		type = kmap_atomic_idx();
		idx = type + KM_TYPE_NR * smp_processor_id();

		if (cache_is_vivt())
			__cpuc_flush_dcache_area((void *)vaddr, PAGE_SIZE);
#ifdef CONFIG_DEBUG_HIGHMEM
		BUG_ON(vaddr != __fix_to_virt(FIX_KMAP_BEGIN + idx));
		set_top_pte(vaddr, __pte(0));
#else
		(void) idx;  /* to kill a warning */
#endif
		kmap_atomic_idx_pop();
	} else if (vaddr >= PKMAP_ADDR(0) && vaddr < PKMAP_ADDR(LAST_PKMAP)) {
		/* this address was obtained through kmap_high_get() */
		kunmap_high(pte_page(pkmap_page_table[PKMAP_NR(vaddr)]));
	}
	pagefault_enable();
}
EXPORT_SYMBOL(__kunmap_atomic);

void *kmap_atomic_pfn(unsigned long pfn)
{
	unsigned long vaddr;
	int idx, type;

	pagefault_disable();

	type = kmap_atomic_idx_push();
	idx = type + KM_TYPE_NR * smp_processor_id();
	vaddr = __fix_to_virt(FIX_KMAP_BEGIN + idx);
#ifdef CONFIG_DEBUG_HIGHMEM
	BUG_ON(!pte_none(get_top_pte(vaddr)));
#endif
	set_top_pte(vaddr, pfn_pte(pfn, kmap_prot));

	return (void *)vaddr;
}

struct page *kmap_atomic_to_page(const void *ptr)
{
	unsigned long vaddr = (unsigned long)ptr;

	if (vaddr < FIXADDR_START)
		return virt_to_page(ptr);

	return pte_page(get_top_pte(vaddr));
}

#ifdef CONFIG_ARCH_WANT_KMAP_ATOMIC_FLUSH
static void kmap_remove_unused_cpu(int cpu)
{
	int start_idx, idx, type;

	pagefault_disable();
	type = kmap_atomic_idx();
	start_idx = type + 1 + KM_TYPE_NR * cpu;

	for (idx = start_idx; idx < KM_TYPE_NR + KM_TYPE_NR * cpu; idx++) {
		unsigned long vaddr = __fix_to_virt(FIX_KMAP_BEGIN + idx);
		pte_t ptep;

		ptep = get_top_pte(vaddr);
		if (ptep)
			set_top_pte(vaddr, __pte(0));
	}
	pagefault_enable();
}

static void kmap_remove_unused(void *unused)
{
	kmap_remove_unused_cpu(smp_processor_id());
}

void kmap_atomic_flush_unused(void)
{
	on_each_cpu(kmap_remove_unused, NULL, 1);
}

static int hotplug_kmap_atomic_callback(struct notifier_block *nfb,
					unsigned long action, void *hcpu)
{
	switch (action & (~CPU_TASKS_FROZEN)) {
	case CPU_DYING:
		kmap_remove_unused_cpu((int)hcpu);
		break;
	default:
		break;
	}

	return NOTIFY_OK;
}

static struct notifier_block hotplug_kmap_atomic_notifier = {
	.notifier_call = hotplug_kmap_atomic_callback,
};

static int __init init_kmap_atomic(void)
{
	return register_hotcpu_notifier(&hotplug_kmap_atomic_notifier);
}
early_initcall(init_kmap_atomic);
#endif