ioremap.c

/*
 * arch/i386/mm/ioremap.c
 *
 * Re-map IO memory to kernel address space so that we can access it.
 * This is needed for high PCI addresses that aren't mapped in the
 * 640k-1MB IO memory area on PC's
 *
 * (C) Copyright 1995 1996 Linus Torvalds
 */

#include <linux/vmalloc.h>
#include <linux/init.h>
#include <linux/slab.h>
#include <linux/module.h>
#include <asm/io.h>
#include <asm/fixmap.h>
#include <asm/cacheflush.h>
#include <asm/tlbflush.h>
#include <asm/pgtable.h>

#define ISA_START_ADDRESS	0xa0000
#define ISA_END_ADDRESS		0x100000

static int ioremap_pte_range(pmd_t *pmd, unsigned long addr,
		unsigned long end, unsigned long phys_addr, unsigned long flags)
{
	pte_t *pte;
	unsigned long pfn;

	pfn = phys_addr >> PAGE_SHIFT;
	pte = pte_alloc_kernel(&init_mm, pmd, addr);
	if (!pte)
		return -ENOMEM;
	do {
		BUG_ON(!pte_none(*pte));
		set_pte(pte, pfn_pte(pfn, __pgprot(_PAGE_PRESENT | _PAGE_RW | 
					_PAGE_DIRTY | _PAGE_ACCESSED | flags)));
		pfn++;
	} while (pte++, addr += PAGE_SIZE, addr != end);
	return 0;
}

static inline int ioremap_pmd_range(pud_t *pud, unsigned long addr,
		unsigned long end, unsigned long phys_addr, unsigned long flags)
{
	pmd_t *pmd;
	unsigned long next;

	phys_addr -= addr;
	pmd = pmd_alloc(&init_mm, pud, addr);
	if (!pmd)
		return -ENOMEM;
	do {
		next = pmd_addr_end(addr, end);
		if (ioremap_pte_range(pmd, addr, next, phys_addr + addr, flags))
			return -ENOMEM;
	} while (pmd++, addr = next, addr != end);
	return 0;
}

static inline int ioremap_pud_range(pgd_t *pgd, unsigned long addr,
		unsigned long end, unsigned long phys_addr, unsigned long flags)
{
	pud_t *pud;
	unsigned long next;

	phys_addr -= addr;
	pud = pud_alloc(&init_mm, pgd, addr);
	if (!pud)
		return -ENOMEM;
	do {
		next = pud_addr_end(addr, end);
		if (ioremap_pmd_range(pud, addr, next, phys_addr + addr, flags))
			return -ENOMEM;
	} while (pud++, addr = next, addr != end);
	return 0;
}

static int ioremap_page_range(unsigned long addr,
		unsigned long end, unsigned long phys_addr, unsigned long flags)
{
	pgd_t *pgd;
	unsigned long next;
	int err;

	BUG_ON(addr >= end);
	flush_cache_all();
	phys_addr -= addr;
	pgd = pgd_offset_k(addr);
	spin_lock(&init_mm.page_table_lock);
	do {
		next = pgd_addr_end(addr, end);
		err = ioremap_pud_range(pgd, addr, next, phys_addr+addr, flags);
		if (err)
			break;
	} while (pgd++, addr = next, addr != end);
	spin_unlock(&init_mm.page_table_lock);
	flush_tlb_all();
	return err;
}

/*
 * Generic mapping function (not visible outside):
 */

/*
 * Remap an arbitrary physical address space into the kernel virtual
 * address space. Needed when the kernel wants to access high addresses
 * directly.
 *
 * NOTE! We need to allow non-page-aligned mappings too: we will obviously
 * have to convert them into an offset in a page-aligned mapping, but the
 * caller shouldn't need to know that small detail.
 */
void __iomem * __ioremap(unsigned long phys_addr, unsigned long size, unsigned long flags)
{
	void __iomem * addr;
	struct vm_struct * area;
	unsigned long offset, last_addr;

	/* Don't allow wraparound or zero size */
	last_addr = phys_addr + size - 1;
	if (!size || last_addr < phys_addr)
		return NULL;

	/*
	 * Don't remap the low PCI/ISA area, it's always mapped..
	 */
	if (phys_addr >= ISA_START_ADDRESS && last_addr < ISA_END_ADDRESS)
		return (void __iomem *) phys_to_virt(phys_addr);

	/*
	 * Don't allow anybody to remap normal RAM that we're using..
	 */
	if (phys_addr <= virt_to_phys(high_memory - 1)) {
		char *t_addr, *t_end;
		struct page *page;

		t_addr = __va(phys_addr);
		t_end = t_addr + (size - 1);
	   
		for(page = virt_to_page(t_addr); page <= virt_to_page(t_end); page++)
			if(!PageReserved(page))
				return NULL;
	}

	/*
	 * Mappings have to be page-aligned
	 */
	offset = phys_addr & ~PAGE_MASK;
	phys_addr &= PAGE_MASK;
	size = PAGE_ALIGN(last_addr+1) - phys_addr;

	/*
	 * Ok, go for it..
	 */
	area = get_vm_area(size, VM_IOREMAP | (flags << 20));
	if (!area)
		return NULL;
	area->phys_addr = phys_addr;
	addr = (void __iomem *) area->addr;
	if (ioremap_page_range((unsigned long) addr,
			(unsigned long) addr + size, phys_addr, flags)) {
		vunmap((void __force *) addr);
		return NULL;
	}
	return (void __iomem *) (offset + (char __iomem *)addr);
}
EXPORT_SYMBOL(__ioremap);

/**
 * ioremap_nocache     -   map bus memory into CPU space
 * @offset:    bus address of the memory
 * @size:      size of the resource to map
 *
 * ioremap_nocache performs a platform specific sequence of operations to
 * make bus memory CPU accessible via the readb/readw/readl/writeb/
 * writew/writel functions and the other mmio helpers. The returned
 * address is not guaranteed to be usable directly as a virtual
 * address. 
 *
 * This version of ioremap ensures that the memory is marked uncachable
 * on the CPU as well as honouring existing caching rules from things like
 * the PCI bus. Note that there are other caches and buffers on many 
 * busses. In particular driver authors should read up on PCI writes
 *
 * It's useful if some control registers are in such an area and
 * write combining or read caching is not desirable:
 * 
 * Must be freed with iounmap.
 */

void __iomem *ioremap_nocache (unsigned long phys_addr, unsigned long size)
{
	unsigned long last_addr;
	void __iomem *p = __ioremap(phys_addr, size, _PAGE_PCD);
	if (!p) 
		return p; 

	/* Guaranteed to be > phys_addr, as per __ioremap() */
	last_addr = phys_addr + size - 1;

	if (last_addr < virt_to_phys(high_memory) - 1) {
		struct page *ppage = virt_to_page(__va(phys_addr));		
		unsigned long npages;

		phys_addr &= PAGE_MASK;

		/* This might overflow and become zero.. */
		last_addr = PAGE_ALIGN(last_addr);

		/* .. but that's ok, because modulo-2**n arithmetic will make
	 	* the page-aligned "last - first" come out right.
	 	*/
		npages = (last_addr - phys_addr) >> PAGE_SHIFT;

		if (change_page_attr(ppage, npages, PAGE_KERNEL_NOCACHE) < 0) { 
			iounmap(p); 
			p = NULL;
		}
		global_flush_tlb();
	}

	return p;					
}
EXPORT_SYMBOL(ioremap_nocache);

void iounmap(volatile void __iomem *addr)
{
	struct vm_struct *p;
	if ((void __force *) addr <= high_memory) 
		return;

	/*
	 * __ioremap special-cases the PCI/ISA range by not instantiating a
	 * vm_area and by simply returning an address into the kernel mapping
	 * of ISA space.   So handle that here.
	 */
	if (addr >= phys_to_virt(ISA_START_ADDRESS) &&
			addr < phys_to_virt(ISA_END_ADDRESS))
		return;

	write_lock(&vmlist_lock);
	p = __remove_vm_area((void *) (PAGE_MASK & (unsigned long __force) addr));
	if (!p) { 
		printk("iounmap: bad address %p\n", addr);
		goto out_unlock;
	}

	if ((p->flags >> 20) && p->phys_addr < virt_to_phys(high_memory) - 1) {
		change_page_attr(virt_to_page(__va(p->phys_addr)),
				 p->size >> PAGE_SHIFT,
				 PAGE_KERNEL);
		global_flush_tlb();
	} 
out_unlock:
	write_unlock(&vmlist_lock);
	kfree(p); 
}
EXPORT_SYMBOL(iounmap);

void __init *bt_ioremap(unsigned long phys_addr, unsigned long size)
{
	unsigned long offset, last_addr;
	unsigned int nrpages;
	enum fixed_addresses idx;

	/* Don't allow wraparound or zero size */
	last_addr = phys_addr + size - 1;
	if (!size || last_addr < phys_addr)
		return NULL;

	/*
	 * Don't remap the low PCI/ISA area, it's always mapped..
	 */
	if (phys_addr >= ISA_START_ADDRESS && last_addr < ISA_END_ADDRESS)
		return phys_to_virt(phys_addr);

	/*
	 * Mappings have to be page-aligned
	 */
	offset = phys_addr & ~PAGE_MASK;
	phys_addr &= PAGE_MASK;
	size = PAGE_ALIGN(last_addr) - phys_addr;

	/*
	 * Mappings have to fit in the FIX_BTMAP area.
	 */
	nrpages = size >> PAGE_SHIFT;
	if (nrpages > NR_FIX_BTMAPS)
		return NULL;

	/*
	 * Ok, go for it..
	 */
	idx = FIX_BTMAP_BEGIN;
	while (nrpages > 0) {
		set_fixmap(idx, phys_addr);
		phys_addr += PAGE_SIZE;
		--idx;
		--nrpages;
	}
	return (void*) (offset + fix_to_virt(FIX_BTMAP_BEGIN));
}

void __init bt_iounmap(void *addr, unsigned long size)
{
	unsigned long virt_addr;
	unsigned long offset;
	unsigned int nrpages;
	enum fixed_addresses idx;

	virt_addr = (unsigned long)addr;
	if (virt_addr < fix_to_virt(FIX_BTMAP_BEGIN))
		return;
	offset = virt_addr & ~PAGE_MASK;
	nrpages = PAGE_ALIGN(offset + size - 1) >> PAGE_SHIFT;

	idx = FIX_BTMAP_BEGIN;
	while (nrpages > 0) {
		clear_fixmap(idx);
		--idx;
		--nrpages;
	}
}