arm9_u-boot-2012.4.1分析

小鱼儿 2023-06-01 06:20 4阅读 0赞

u-boot启动方式：

1.设置CPU为管理者模式

start_code:
        /*
         * set the cpu to SVC32 mode
         */
        mrs    r0, cpsr
        bic    r0, r0, #0x1f
        orr    r0, r0, #0xd3
        msr    cpsr, r0

2.关看门狗，关中断, 设置时钟频率

#  define pWTCON    0x53000000
    #  define INTMSK    0x4A000008    /* Interrupt-Controller base addresses */
    #  define INTSUBMSK    0x4A00001C
    #  define CLKDIVN    0x4C000014    /* clock divisor register */
    # endif
    
        ldr    r0, =pWTCON
        mov    r1, #0x0
        str    r1, [r0]
    
        /*
         * mask all IRQs by setting all bits in the INTMR - default
         */
        mov    r1, #0xffffffff
        ldr    r0, =INTMSK
        str    r1, [r0]
    # if defined(CONFIG_S3C2410)
        ldr    r1, =0x3ff
        ldr    r0, =INTSUBMSK
        str    r1, [r0]
    # endif
    
        /* FCLK:HCLK:PCLK = 1:2:4 */
        /* default FCLK is 120 MHz ! */
        ldr    r0, =CLKDIVN
        mov    r1, #3
        str    r1, [r0]
    #endif    /* CONFIG_S3C24X0 */

3.关MMU,初始各个bank

#ifndef CONFIG_SKIP_LOWLEVEL_INIT
           bl    cpu_init_crit

cpu_init_crit:
        /*
         * flush v4 I/D caches
         */
        mov    r0, #0
        mcr    p15, 0, r0, c7, c7, 0    /* flush v3/v4 cache */
        mcr    p15, 0, r0, c8, c7, 0    /* flush v4 TLB */
    
        /*
         * disable MMU stuff and caches
         */
        mrc    p15, 0, r0, c1, c0, 0
        bic    r0, r0, #0x00002300    @ clear bits 13, 9:8 (--V- --RS)
        bic    r0, r0, #0x00000087    @ clear bits 7, 2:0 (B--- -CAM)
        orr    r0, r0, #0x00000002    @ set bit 2 (A) Align
        orr    r0, r0, #0x00001000    @ set bit 12 (I) I-Cache
        mcr    p15, 0, r0, c1, c0, 0
    
        /*
         * before relocating, we have to setup RAM timing
         * because memory timing is board-dependend, you will
         * find a lowlevel_init.S in your board directory.
         */
        mov    ip, lr
    
        bl    lowlevel_init
    
        mov    lr, ip
        mov    pc, lr
    #endif /* CONFIG_SKIP_LOWLEVEL_INIT */

lowlevel_init:
        /* memory control configuration */
        /* make r0 relative the current location so that it */
        /* reads SMRDATA out of FLASH rather than memory ! */
        ldr     r0, =SMRDATA
        ldr    r1, _TEXT_BASE
        sub    r0, r0, r1
        ldr    r1, =BWSCON    /* Bus Width Status Controller */
        add     r2, r0, #13*4
    0:
        ldr     r3, [r0], #4
        str     r3, [r1], #4
        cmp     r2, r0
        bne     0b
    
        /* everything is fine now */
        mov    pc, lr
    
        .ltorg
    /* the literal pools origin */
    
    SMRDATA:
        .word (0+(B1_BWSCON<<4)+(B2_BWSCON<<8)+(B3_BWSCON<<12)+(B4_BWSCON<<16)+(B5_BWSCON<<20)+(B6_BWSCON<<24)+(B7_BWSCON<<28))
        .word ((B0_Tacs<<13)+(B0_Tcos<<11)+(B0_Tacc<<8)+(B0_Tcoh<<6)+(B0_Tah<<4)+(B0_Tacp<<2)+(B0_PMC))
        .word ((B1_Tacs<<13)+(B1_Tcos<<11)+(B1_Tacc<<8)+(B1_Tcoh<<6)+(B1_Tah<<4)+(B1_Tacp<<2)+(B1_PMC))
        .word ((B2_Tacs<<13)+(B2_Tcos<<11)+(B2_Tacc<<8)+(B2_Tcoh<<6)+(B2_Tah<<4)+(B2_Tacp<<2)+(B2_PMC))
        .word ((B3_Tacs<<13)+(B3_Tcos<<11)+(B3_Tacc<<8)+(B3_Tcoh<<6)+(B3_Tah<<4)+(B3_Tacp<<2)+(B3_PMC))
        .word ((B4_Tacs<<13)+(B4_Tcos<<11)+(B4_Tacc<<8)+(B4_Tcoh<<6)+(B4_Tah<<4)+(B4_Tacp<<2)+(B4_PMC))
        .word ((B5_Tacs<<13)+(B5_Tcos<<11)+(B5_Tacc<<8)+(B5_Tcoh<<6)+(B5_Tah<<4)+(B5_Tacp<<2)+(B5_PMC))
        .word ((B6_MT<<15)+(B6_Trcd<<2)+(B6_SCAN))
        .word ((B7_MT<<15)+(B7_Trcd<<2)+(B7_SCAN))
        .word ((REFEN<<23)+(TREFMD<<22)+(Trp<<20)+(Trc<<18)+(Tchr<<16)+REFCNT)
        .word 0x32
        .word 0x30
        .word 0x30

4.进入board\_init\_f()函数 (初始化定时器,GPIO,串口等,划分内存区域: 清空gd指向的结构体、通过init\_sequence函数数组,来初始化各个函数以及逐步填充gd结构体，最后划分内存区域,将数据保存在gd里,然后调用relocate\_code()对uboot重定位,gd是用来传递给内核的参数)

call_board_init_f:
           ldr   sp, =(CONFIG_SYS_INIT_SP_ADDR) //CONFIG_SYS_INIT_SP_ADDR=0x30000f80
           bic   sp, sp, #7         //sp=0x30000f80
           ldr   r0,=0x00000000
           bl    board_init_f

反汇编：arm-linux-objdump -D u-boot>u-boot.dis

00000098 <call_board_init_f>:
          98:    e59fd3d8     ldr    sp, [pc, #984]    ; 478 <fiq+0x58>
    .......
         478: 30000f80 .word 0x30000f80

void board_init_f(ulong bootflag)
    {
        bd_t *bd;
        init_fnc_t **init_fnc_ptr;
        gd_t *id;
        ulong addr, addr_sp;
    #ifdef CONFIG_PRAM
        ulong reg;
    #endif
    
        bootstage_mark_name(BOOTSTAGE_ID_START_UBOOT_F, "board_init_f");
    
        /* Pointer is writable since we allocated a register for it */
        gd = (gd_t *) ((CONFIG_SYS_INIT_SP_ADDR) & ~0x07);
        /* compiler optimization barrier needed for GCC >= 3.4 */
        __asm__ __volatile__("": : :"memory");
    
        memset((void *)gd, 0, sizeof(gd_t));
    
        gd->mon_len = _bss_end_ofs;
    #ifdef CONFIG_OF_EMBED
        /* Get a pointer to the FDT */
        gd->fdt_blob = _binary_dt_dtb_start;
    #elif defined CONFIG_OF_SEPARATE
        /* FDT is at end of image */
        gd->fdt_blob = (void *)(_end_ofs + _TEXT_BASE);
    #endif
        /* Allow the early environment to override the fdt address */
        gd->fdt_blob = (void *)getenv_ulong("fdtcontroladdr", 16,
                            (uintptr_t)gd->fdt_blob);
    
        for (init_fnc_ptr = init_sequence; *init_fnc_ptr; ++init_fnc_ptr) {
            if ((*init_fnc_ptr)() != 0) {
                hang ();
            }
        }
    
    #ifdef CONFIG_OF_CONTROL
        /* For now, put this check after the console is ready */
        if (fdtdec_prepare_fdt()) {
            panic("** CONFIG_OF_CONTROL defined but no FDT - please see "
                "doc/README.fdt-control");
        }
    #endif
    
        debug("monitor len: %08lX\n", gd->mon_len);
        /*
         * Ram is setup, size stored in gd !!
         */
        debug("ramsize: %08lX\n", gd->ram_size);
    #if defined(CONFIG_SYS_MEM_TOP_HIDE)
        /*
         * Subtract specified amount of memory to hide so that it won't
         * get "touched" at all by U-Boot. By fixing up gd->ram_size
         * the Linux kernel should now get passed the now "corrected"
         * memory size and won't touch it either. This should work
         * for arch/ppc and arch/powerpc. Only Linux board ports in
         * arch/powerpc with bootwrapper support, that recalculate the
         * memory size from the SDRAM controller setup will have to
         * get fixed.
         */
        gd->ram_size -= CONFIG_SYS_MEM_TOP_HIDE;
    #endif
    
        addr = CONFIG_SYS_SDRAM_BASE + gd->ram_size;
    
    #ifdef CONFIG_LOGBUFFER
    #ifndef CONFIG_ALT_LB_ADDR
        /* reserve kernel log buffer */
        addr -= (LOGBUFF_RESERVE);
        debug("Reserving %dk for kernel logbuffer at %08lx\n", LOGBUFF_LEN,
            addr);
    #endif
    #endif
    
    #ifdef CONFIG_PRAM
        /*
         * reserve protected RAM
         */
        reg = getenv_ulong("pram", 10, CONFIG_PRAM);
        addr -= (reg << 10);        /* size is in kB */
        debug("Reserving %ldk for protected RAM at %08lx\n", reg, addr);
    #endif /* CONFIG_PRAM */
    
    #if !(defined(CONFIG_SYS_ICACHE_OFF) && defined(CONFIG_SYS_DCACHE_OFF))
        /* reserve TLB table */
        addr -= (4096 * 4);
    
        /* round down to next 64 kB limit */
        addr &= ~(0x10000 - 1);
    
        gd->tlb_addr = addr;
        debug("TLB table at: %08lx\n", addr);
    #endif
    
        /* round down to next 4 kB limit */
        addr &= ~(4096 - 1);
        debug("Top of RAM usable for U-Boot at: %08lx\n", addr);
    
    #ifdef CONFIG_LCD
    #ifdef CONFIG_FB_ADDR
        gd->fb_base = CONFIG_FB_ADDR;
    #else
        /* reserve memory for LCD display (always full pages) */
        addr = lcd_setmem(addr);
        gd->fb_base = addr;
    #endif /* CONFIG_FB_ADDR */
    #endif /* CONFIG_LCD */
    
        /*
         * reserve memory for U-Boot code, data & bss
         * round down to next 4 kB limit
         */
        addr -= gd->mon_len;
        addr &= ~(4096 - 1);
    
        debug("Reserving %ldk for U-Boot at: %08lx\n", gd->mon_len >> 10, addr);
    
    #ifndef CONFIG_SPL_BUILD
        /*
         * reserve memory for malloc() arena
         */
        addr_sp = addr - TOTAL_MALLOC_LEN;
        debug("Reserving %dk for malloc() at: %08lx\n",
                TOTAL_MALLOC_LEN >> 10, addr_sp);
        /*
         * (permanently) allocate a Board Info struct
         * and a permanent copy of the "global" data
         */
        addr_sp -= sizeof (bd_t);
        bd = (bd_t *) addr_sp;
        gd->bd = bd;
        debug("Reserving %zu Bytes for Board Info at: %08lx\n",
                sizeof (bd_t), addr_sp);
    
    #ifdef CONFIG_MACH_TYPE
        gd->bd->bi_arch_number = CONFIG_MACH_TYPE; /* board id for Linux */
    #endif
    
        addr_sp -= sizeof (gd_t);
        id = (gd_t *) addr_sp;
        debug("Reserving %zu Bytes for Global Data at: %08lx\n",
                sizeof (gd_t), addr_sp);
    
        /* setup stackpointer for exeptions */
        gd->irq_sp = addr_sp;
    #ifdef CONFIG_USE_IRQ
        addr_sp -= (CONFIG_STACKSIZE_IRQ+CONFIG_STACKSIZE_FIQ);
        debug("Reserving %zu Bytes for IRQ stack at: %08lx\n",
            CONFIG_STACKSIZE_IRQ+CONFIG_STACKSIZE_FIQ, addr_sp);
    #endif
        /* leave 3 words for abort-stack    */
        addr_sp -= 12;
    
        /* 8-byte alignment for ABI compliance */
        addr_sp &= ~0x07;
    #else
        addr_sp += 128;    /* leave 32 words for abort-stack   */
        gd->irq_sp = addr_sp;
    #endif
    
        debug("New Stack Pointer is: %08lx\n", addr_sp);
    
    #ifdef CONFIG_POST
        post_bootmode_init();
        post_run(NULL, POST_ROM | post_bootmode_get(0));
    #endif
    
        gd->bd->bi_baudrate = gd->baudrate;
        /* Ram ist board specific, so move it to board code ... */
        dram_init_banksize();
        display_dram_config();    /* and display it */
    
        gd->relocaddr = addr;
        gd->start_addr_sp = addr_sp;
        gd->reloc_off = addr - _TEXT_BASE;
        debug("relocation Offset is: %08lx\n", gd->reloc_off);
        memcpy(id, (void *)gd, sizeof(gd_t));
    
        relocate_code(addr_sp, id, addr);
    
        /* NOTREACHED - relocate_code() does not return */
    }

init_fnc_t *init_sequence[] = {
    #if defined(CONFIG_ARCH_CPU_INIT)
        arch_cpu_init,        /* basic arch cpu dependent setup */
    #endif
    #if defined(CONFIG_BOARD_EARLY_INIT_F)
        board_early_init_f,
    #endif
    #ifdef CONFIG_OF_CONTROL
        fdtdec_check_fdt,
    #endif
        timer_init,        /* initialize timer */
    #ifdef CONFIG_FSL_ESDHC
        get_clocks,
    #endif
        env_init,        /* initialize environment */
        init_baudrate,        /* initialze baudrate settings */
        serial_init,        /* serial communications setup */
        console_init_f,        /* stage 1 init of console */
        display_banner,        /* say that we are here */
    #if defined(CONFIG_DISPLAY_CPUINFO)
        print_cpuinfo,        /* display cpu info (and speed) */
    #endif
    #if defined(CONFIG_DISPLAY_BOARDINFO)
        checkboard,        /* display board info */
    #endif
    #if defined(CONFIG_HARD_I2C) || defined(CONFIG_SOFT_I2C)
        init_func_i2c,
    #endif
        dram_init,        /* configure available RAM banks */
        NULL,
    };

5.重定位 (复制uboot,然后修改SDRAM上的uboot链接地址)

relocate\_code:  
　　mov r4, r0 /\* save addr\_sp \*/  
　　mov r5, r1 /\* save addr of gd \*/  
　　mov r6, r2 /\* save addr of destination \*/

/\* Set up the stack \*/  
stack\_setup:  
　　mov sp, r4

adr r0, \_start  
　　cmp r0, r6  
　　beq clear\_bss /\* skip relocation \*/  
　　mov r1, r6 /\* r1 <- scratch for copy\_loop \*/  
　　ldr r3, \_bss\_start\_ofs  
　　add r2, r0, r3 /\* r2 <- source end address \*/

copy_loop:
        ldmia    r0!, {r9-r10}        /* copy from source address [r0]    */
        stmia    r1!, {r9-r10}        /* copy to   target address [r1]    */
        cmp    r0, r2            /* until source end address [r2]    */
        blo    copy_loop
    
    #ifndef CONFIG_SPL_BUILD
        /*
         * fix .rel.dyn relocations
         */
        ldr    r0, _TEXT_BASE        /* r0 <- Text base */
        sub    r9, r6, r0        /* r9 <- relocation offset */
        ldr    r10, _dynsym_start_ofs    /* r10 <- sym table ofs */
        add    r10, r10, r0        /* r10 <- sym table in FLASH */
        ldr    r2, _rel_dyn_start_ofs    /* r2 <- rel dyn start ofs */
        add    r2, r2, r0        /* r2 <- rel dyn start in FLASH */
        ldr    r3, _rel_dyn_end_ofs    /* r3 <- rel dyn end ofs */
        add    r3, r3, r0        /* r3 <- rel dyn end in FLASH */
    fixloop:
        ldr    r0, [r2]        /* r0 <- location to fix up, IN FLASH! */
        add    r0, r0, r9        /* r0 <- location to fix up in RAM */
        ldr    r1, [r2, #4]
        and    r7, r1, #0xff
        cmp    r7, #23            /* relative fixup? */
        beq    fixrel
        cmp    r7, #2            /* absolute fixup? */
        beq    fixabs
        /* ignore unknown type of fixup */
        b    fixnext
    fixabs:
        /* absolute fix: set location to (offset) symbol value */
        mov    r1, r1, LSR #4        /* r1 <- symbol index in .dynsym */
        add    r1, r10, r1        /* r1 <- address of symbol in table */
        ldr    r1, [r1, #4]        /* r1 <- symbol value */
        add    r1, r1, r9        /* r1 <- relocated sym addr */
        b    fixnext
    fixrel:
        /* relative fix: increase location by offset */
        ldr    r1, [r0]
        add    r1, r1, r9
    fixnext:
        str    r1, [r0]
        add    r2, r2, #8        /* each rel.dyn entry is 8 bytes */
        cmp    r2, r3
        blo    fixloop
    #endif

6.清bss

clear_bss:
    #ifndef CONFIG_SPL_BUILD
        ldr    r0, _bss_start_ofs
        ldr    r1, _bss_end_ofs
        mov    r4, r6            /* reloc addr */
        add    r0, r0, r4
        add    r1, r1, r4
        mov    r2, #0x00000000        /* clear                */
    
    clbss_l:str    r2, [r0]        /* clear loop...            */
        add    r0, r0, #4
        cmp    r0, r1
        bne    clbss_l
    
        bl coloured_LED_init
        bl red_led_on
    #endif

7. 跳转到board\_init\_r()函数,启动流程结束

ldr    r0, _board_init_r_ofs
        adr    r1, _start
        add    lr, r0, r1
        add    lr, lr, r9
        /* setup parameters for board_init_r */
        mov    r0, r5        /* gd_t */
        mov    r1, r6        /* dest_addr */
        /* jump to it ... */
        mov    pc, lr
    
    _board_init_r_ofs:
        .word board_init_r - _start

void board\_init\_r(gd\_t \*id, ulong dest\_addr)  
\{

//硬件初始化...
    .........
    for (;;) {
            main_loop();
        }
    .........
    
    }

转载于:https://www.cnblogs.com/lzd626/p/11588310.html