TQ2440的watchdog linux驱动在内核源码linux-2.6.30.4的: ./drivers/watchdog/s3c2410_wdt.c下
1. watchdog ioremap的过程:
res->start=0x53000000 //物理地址
wdt_base=0xc5400000 //虚拟地址
wdt_base = ioremap(res->start, size);
将物理地址res->start映射到了虚拟地址0xc5400000处,映射大小为:size=0x100000.
注: 不知道为什么刚开始这个size=8,后来就成了0x100000(1M)。
2. arch/arm/include/asm/io.h中,找到ioremap的定义:
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//出现两个ioremap
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#ifndef __arch_ioremap
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#define ioremap(cookie,size) __arm_ioremap(cookie, size, MT_DEVICE)
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#define ioremap_nocache(cookie,size) __arm_ioremap(cookie, size, MT_DEVICE)
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#define ioremap_cached(cookie,size) __arm_ioremap(cookie, size, MT_DEVICE_CACHED)
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#define ioremap_wc(cookie,size) __arm_ioremap(cookie, size, MT_DEVICE_WC)
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#define iounmap(cookie) __iounmap(cookie)
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#else
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#define ioremap(cookie,size) __arch_ioremap((cookie), (size), MT_DEVICE)
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#define ioremap_nocache(cookie,size) __arch_ioremap((cookie), (size), MT_DEVICE)
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#define ioremap_cached(cookie,size) __arch_ioremap((cookie), (size), MT_DEVICE_CACHED)
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#define ioremap_wc(cookie,size) __arch_ioremap((cookie), (size), MT_DEVICE_WC)
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#define iounmap(cookie) __arch_iounmap(cookie)
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#endif
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没有定义 #ifndef __arch_ioremap,所以是
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#define MT_DEVICE 0
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#define ioremap(cookie,size) __arm_ioremap(cookie, size, MT_DEVICE)
3.在arch/arm/mm/ioremap.c中
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__arm_ioremap(cookie, size, MT_DEVICE) 也有两个定义,一个是在nommu.c中,一个是在arch/arm/mm/ioremap.c中,所以很明显进入 arch/arm/mm/ioremap.c中:
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//这个函数将物理地址phys_addr拆成两部分高20位的页帧号(Page Frame Number)pfn和低12位的页内偏移地址offset
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void __iomem *
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__arm_ioremap(unsigned long phys_addr, size_t size, unsigned int mtype)
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{
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unsigned long last_addr;
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unsigned long offset = phys_addr & ~PAGE_MASK;
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unsigned long pfn = __phys_to_pfn(phys_addr);
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/*
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* Don't allow wraparound or zero size
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*/
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last_addr = phys_addr + size - 1;
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if (!size || last_addr < phys_addr)
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return NULL;
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//此处打印值如下: last_addr=0x530fffff, size=0x100000, offset=0x0, pfn=0x53000
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return __arm_ioremap_pfn(pfn, offset, size, mtype);
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}
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EXPORT_SYMBOL(__arm_ioremap);
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/*
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* Convert a physical address to a Page Frame Number and back
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*/
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#define PAGE_SHIFT 12
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#define __phys_to_pfn(paddr) ((paddr) >> PAGE_SHIFT)
4. 在arch/arm/mm/ioremap.c中
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/*
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* Remap an arbitrary physical address space into the kernel virtual
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* address space. Needed when the kernel wants to access high addresses
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* directly.
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*
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* We need to allow non-page-aligned mappings too: we will obviously
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* have to convert them into an offset in a page-aligned mapping, but the
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* caller shouldn't need to know that small detail.
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*
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* 'flags' are the extra L_PTE_ flags that you want to specify for this
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* mapping. See <asm/pgtable.h> for more information.
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*/
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void __iomem *
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__arm_ioremap_pfn(unsigned long pfn, unsigned long offset, size_t size,
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unsigned int mtype)
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{
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const struct mem_type *type;
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int err;
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unsigned long addr;
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struct vm_struct * area;
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/*
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* High mappings must be supersection aligned
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*/
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if (pfn >= 0x100000 && (__pfn_to_phys(pfn) & ~SUPERSECTION_MASK))
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return NULL;
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type = get_mem_type(mtype);
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if (!type)
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return NULL;
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/*
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* Page align the mapping size, taking account of any offset.
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*/
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size = PAGE_ALIGN(offset + size);
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area = get_vm_area(size, VM_IOREMAP); //分配虚拟地址空间
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if (!area)
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return NULL;
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addr = (unsigned long)area->addr;
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//此处打印出的地址: addr=0xc5400000
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#ifndef CONFIG_SMP //不进入此处
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if (DOMAIN_IO == 0 &&
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(((cpu_architecture() >= CPU_ARCH_ARMv6) && (get_cr() & CR_XP)) ||
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cpu_is_xsc3()) && pfn >= 0x100000 &&
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!((__pfn_to_phys(pfn) | size | addr) & ~SUPERSECTION_MASK)) {
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area->flags |= VM_ARM_SECTION_MAPPING;
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err = remap_area_supersections(addr, pfn, size, type);
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} else if (!((__pfn_to_phys(pfn) | size | addr) & ~PMD_MASK)) {
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area->flags |= VM_ARM_SECTION_MAPPING;
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err = remap_area_sections(addr, pfn, size, type);
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} else
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#endif
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err = remap_area_pages(addr, pfn, size, type);
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if (err) {
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vunmap((void *)addr);
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return NULL;
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}
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flush_cache_vmap(addr, addr + size);
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return (void __iomem *) (offset + addr);
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}
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EXPORT_SYMBOL(__arm_ioremap_pfn);
area = get_vm_area(size, VM_IOREMAP); //分配虚拟地址空间
err = remap_area_pages(addr, pfn, size, type);
这两个函数。
5. 在arch/arm/mm/ioremap.c中
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static int
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remap_area_sections(unsigned long virt, unsigned long pfn,
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size_t size, const struct mem_type *type)
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{
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unsigned long addr = virt, end = virt + size;
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pgd_t *pgd;
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/*
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* Remove and free any PTE-based mapping, and
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* sync the current kernel mapping.
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*/
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unmap_area_sections(virt, size);
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pgd = pgd_offset_k(addr);
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do {
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pmd_t *pmd = pmd_offset(pgd, addr);
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pmd[0] = __pmd(__pfn_to_phys(pfn) | type->prot_sect);
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pfn += SZ_1M >> PAGE_SHIFT;
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pmd[1] = __pmd(__pfn_to_phys(pfn) | type->prot_sect);
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pfn += SZ_1M >> PAGE_SHIFT;
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flush_pmd_entry(pmd);
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addr += PGDIR_SIZE;
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pgd++;
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} while (addr < end);
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return 0;
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}
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