设备寄存器静态映射的建立

来源：互联网发布：c语言求质数用while 编辑：程序博客网时间：2024/06/10 00:18

何时建立这个映射

* 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(struct machine_desc *mdesc)
{
   /*
   * Ask the machine support to map in the statically mapped devices.
   */
   if (mdesc->map_io)
       mdesc->map_io();
}

平台具体的函数

MACHINE_START(TL7689_PAD_TEST, "NUFRONT-TL7689-PAD-TEST")
   .atag_offset   = 0x100,
   .map_io       = tl7689_map_io,
   .init_irq   = pad_test_gic_init,
   .timer       = &tl7689_timer,
   .handle_irq   = gic_handle_irq,
   .init_machine   = tl7689_pad_test_init,
   .init_early   = tl7689_init_early,
MACHINE_END

void __init tl7689_map_io(void)
{
   iotable_init(tl7689_io_desc, ARRAY_SIZE(tl7689_io_desc));
   init_consistent_dma_size(SZ_16M - SZ_2M);
}

主题函数iotable_ini

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

   if (!nr)
       return;

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

   for (md = io_desc; nr; md++, nr--) {
       create_mapping(md, false);
       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;
       vm_area_add_early(vm++);
   }
}

struct map_desc {
   unsigned long virtual;
   unsigned long pfn;
   unsigned long length;
   unsigned int type;
};

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;
}

struct mem_type {
   unsigned int prot_pte;
   unsigned int prot_l1;
   unsigned int prot_sect;
};

create_mapping

* 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, bool force_pages)
{
   unsigned long addr, length, end;
   phys_addr_t phys;
   const struct mem_type *type;
   pgd_t *pgd;
   /*
   *get the type,virtual/phy address, and length
   **/
   type = &mem_types[md->type];

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

   pgd = pgd_offset_k(addr);
   end = addr + length;
   do {
       /*得到下个PGDIR size*/
       unsigned long next = pgd_addr_end(addr, end);

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

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

arch/arm/include/asm/pgtable.h

/* to find an entry in a kernel page-table-directory */
#define pgd_offset_k(addr)   pgd_offset(&init_mm, addr)

#define pgd_offset(mm, addr)   ((mm)->pgd + pgd_index(addr))

/* to find an entry in a page-table-directory */
#define pgd_index(addr)       ((addr) >> PGDIR_SHIFT)

怎样判断是2/3 level?

#ifdef CONFIG_ARM_LPAE
#include <asm/pgtable-3level.h>
#else
#include <asm/pgtable-2level.h>
#endif
crash> sys config | grep "CONFIG_ARM_LPAE"
# CONFIG_ARM_LPAE is not set
所以是 2 level

#define PGDIR_SHIFT       21

/*pgd = pgd_offset_k(addr);
*意思就是以init_mm的pgd为基地址，add右移21位作为Index，从而得到add对应的pgd
**/

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

   do {

       next = pud_addr_end(addr, end);
       alloc_init_section(pud, addr, next, phys, type, force_pages);
       phys += next - addr;
   } while (pud++, addr = next, addr != end);
}

include/asm-generic/pgtable-nopud.h
typedef struct {
    pgd_t pgd;
} pud_t;
SIZE: 8
static inline pud_t * pud_offset(pgd_t * pgd, unsigned long address)
{
   return (pud_t *)pgd;
}

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

   /*
   * Try a section mapping - end, addr and phys must all be aligned
   * to a section boundary. Note that PMDs refer to the individual
   * L1 entries, whereas PGDs refer to a group of L1 entries making
   * up one logical pointer to an L2 table.
   */
   if (type->prot_sect && ((addr | end | phys) & ~SECTION_MASK) == 0 &&
        !force_pages) {
       pmd_t *p = pmd;

       if (addr & SECTION_SIZE)
           pmd++;

       do {
           *pmd = __pmd(phys | type->prot_sect);
           phys += SECTION_SIZE;
       } while (pmd++, addr += SECTION_SIZE, addr != end);

       flush_pmd_entry(p);
   }
}

static inline pmd_t *pmd_offset(pud_t *pud, unsigned long addr)
{
   return (pmd_t *)pud;
}

crash> pmd_t
typedef unsigned int pmd_t;
SIZE: 4

终于向地址里写数了*pmd = __pmd(phys | type->prot_sect);
#define SECTION_SHIFT       20
#define SECTION_SIZE       (1UL << SECTION_SHIFT)
section size 是 1 >> 20:1M .PDIR size为 1 >> 21: 2M,所以要写两次；

#define __pmd(x)        ((pmd_t) { (x) } )
1-0:10 section

以已知的map_desc为例,看map的建立过程

map_desc:
#define TL7689_PRCM_BASE                 0x05821000 /* PRCM 4K */
   {
       .virtual   = IO_ADDRESS(TL7689_PRCM_BASE),
       .pfn       = __phys_to_pfn(TL7689_PRCM_BASE),
       .length       = SZ_4K,
       .type       = MT_DEVICE,
   },

arch/arm/mach-tl7689/include/mach/hardware.h

#define IO_ADDRESS(x) (((x) & 0x03ffffff) + 0xfb000000)
crash> eval (0x05821000 & 0x03ffffff)
hexadecimal: 1821000 (24708KB)

crash> eval (0x01821000 + 0xfb000000)
hexadecimal: fc821000 (4137092KB)

crash> eval (fc821000 >> 21)
hexadecimal: 7e4

crash> eval (7e4*2)
hexadecimal: fc8

crash> eval (0xc0004000+0xfc8)
hexadecimal: c0004fc8

crash> rd c0004fc8
c0004fc8: 00000000 ....

怎么会是0啊？应该是0x05821000? 为什么？

已知虚拟地址fc821000

map_desc:
#define TL7689_PRCM_BASE                 0x05821000 /* PRCM 4K */
   {
       .virtual   = IO_ADDRESS(TL7689_PRCM_BASE),
       .pfn       = __phys_to_pfn(TL7689_PRCM_BASE),
       .length       = SZ_4K,
       .type       = MT_DEVICE,
   },
arch/arm/mach-tl7689/include/mach/hardware.h
#define IO_ADDRESS(x)       (((x) & 0x03ffffff) + 0xfb000000)
crash> eval (0x05821000 & 0x03ffffff)
hexadecimal: 1821000 (24708KB)

crash> eval (0x01821000 + 0xfb000000)
hexadecimal: fc821000 (4137092KB)

/*
* Convert a physical address to a Page Frame Number and back
*/
#define   __phys_to_pfn(paddr)   ((unsigned long)((paddr) >> PAGE_SHIFT))
#define   __pfn_to_phys(pfn)   ((phys_addr_t)(pfn) << PAGE_SHIFT)

/* PAGE_SHIFT determines the page size */
#define PAGE_SHIFT       12
#define PAGE_SIZE       (_AC(1,UL) << PAGE_SHIFT)
#define PAGE_MASK       (~(PAGE_SIZE-1))

crash> eval (0x05821000 >> 12)
hexadecimal: 5821
展开后变为：
   {
       .virtual   = 0xfc821000,
       .pfn       = 0x5821,
       .length       = SZ_4K,
       .type       = MT_DEVICE,
   },
从打印的log看0xfc821000:对应的entry item address 是：0xc0007f20 = 0xc0004000 + 0x3f20
index是0x3f20，不是所说的 0xfc821000 >> 21 = 0x7e4:中间肯定有巧妙的转换
crash> rd 0xc0007f20
c0007f20: 40000000                              ...@

以arm MMU的寻址方式得到虚拟地址对应的entry

crash> eval 0xfc821000 >> 20
crash> eval (0xfc821000 >> 20)
hexadecimal: fc8
crash> eval (fc8 << 2)
hexadecimal: 3f20

wenshuai: trace mmu
wenshuai trace mmu: addr:0xfc821000, phys:0x5821000, length:0x1000
wenshuai trace mmu: pgd:0xc0007f20, end:0xfc822000
wenshuai trace mmu: pmd 0xc0007f20
wenshuai trace mmu: addr:0xfc822000, end:0xfc822000

还是没搞清楚，为什么两者不一致。

如果是以下的方式，两者会一直，哪里进行的处理啊

crash> eval (0xfc821000 >> 21)
hexadecimal: 7e4
crash> eval (7e4/2)
hexadecimal: 3f2
crash> eval (7e40/2)
hexadecimal: 3f20