三星uboot1.1.6源码分析——start.s（8）--C语言部分(2)

上一篇只是开了个头，这一篇我们来分析，那个数组中的函数。

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init_fnc_t *init_sequence[] = {

cpu_init,/* basic cpu dependent setup */

board_init,/* basic board dependent setup */

interrupt_init,/* set up exceptions */

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

dram_init,
/* configure available RAM banks */

display_dram_config,

NULL,

};

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1、

int cpu_init (void)

{

/*

* setup up stacks if necessary 看注释，就明白了，还是那个UBOOT内存映射图，那个图这是太重要了。

*/

#ifdef CONFIG_USE_IRQ

IRQ_STACK_START = _armboot_start - CFG_MALLOC_LEN - CFG_GBL_DATA_SIZE - 4;

FIQ_STACK_START = IRQ_STACK_START - CONFIG_STACKSIZE_IRQ;

#endif

return 0;

}

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2、

int board_init(void)

{

DECLARE_GLOBAL_DATA_PTR;

-------------------------------------------------------------------------------

其中有：

#define DECLARE_GLOBAL_DATA_PTR register volatile gd_t *gd asm ("r8")

------------------------------------------------------------------------------

cs8900_pre_init(); 网卡有关，我们用的不是这个。

gd->bd->bi_arch_number = MACH_TYPE;

gd->bd->bi_boot_params = (PHYS_SDRAM_1+0x100); 有启动参数有关。

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还是和那两个数据结构有关，我在其他博客中有详细的说明。其中有如下定义：

/*

* Architecture magic and machine type

*/

#define MACH_TYPE 1626

#define PHYS_SDRAM_1MEMORY_BASE_ADDRESS /* SDRAM Bank #1 */

#define MEMORY_BASE_ADDRESS0x50000000

这和我们物理内存DRAM的连接方式有关。

--------------------------------------------------------------------------------

#if 0

icache_enable();

dcache_enable();

#endif

return 0;

}

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3、

int interrupt_init(void)

{

S3C64XX_TIMERS *const timers = S3C64XX_GetBase_TIMERS();

----------------------------------------------------------------

typedef struct {

S3C64XX_REG32
TCFG0;

S3C64XX_REG32
TCFG1;

S3C64XX_REG32
TCON;

S3C64XX_TIMERch[4];

S3C64XX_REG32
TCNTB4;

S3C64XX_REG32
TCNTO4;

} S3C64XX_TIMERS;

/* PWM TIMER (see manual chapter 10) */

typedef struct {

S3C64XX_REG32
TCNTB;

S3C64XX_REG32
TCMPB;

S3C64XX_REG32
TCNTO;

} /*__attribute__((__packed__))*/ S3C64XX_TIMER;

typedef vu_char
S3C64XX_REG8;

typedef vu_short S3C64XX_REG16;

typedef vu_long S3C64XX_REG32;

typedef unsigned charuchar;

typedef volatile unsigned long vu_long;

typedef volatile unsigned short vu_short;

typedef volatile unsigned char vu_char;

-------------------------------

static inline S3C64XX_TIMERS * S3C64XX_GetBase_TIMERS(void)

{

return (S3C64XX_TIMERS *)ELFIN_TIMER_BASE;

}

/*

* PWM timer

*/

#define ELFIN_TIMER_BASE0x7F006000

#define TCFG0_REG__REG(0x7F006000)

#define TCFG1_REG__REG(0x7F006004)

#define TCON_REG__REG(0x7F006008)

#define TCNTB0_REG__REG(0x7F00600c)

#define TCMPB0_REG__REG(0x7F006010)

#define TCNTO0_REG__REG(0x7F006014)

#define TCNTB1_REG__REG(0x7F006018)

#define TCMPB1_REG__REG(0x7F00601c)

#define TCNTO1_REG__REG(0x7F006020)

#define TCNTB2_REG__REG(0x7F006024)

#define TCMPB2_REG__REG(0x7F006028)

#define TCNTO2_REG__REG(0x7F00602c)

#define TCNTB3_REG__REG(0x7F006030)

#define TCMPB3_REG__REG(0x7F006034)

#define TCNTO3_REG__REG(0x7F006038)

#define TCNTB4_REG__REG(0x7F00603c)

#define TCNTO4_REG__REG(0x7F006040)

----------------------------------------------------------------

/* use PWM Timer 4 because it has no output */

/* prescaler for Timer 4 is 16 */

timers->TCFG0 = 0x0f00;

------------看图：



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if (timer_load_val == 0) { ------------- int timer_load_val = 0; ( Interrupts.c (cpu\s3c64xx) )

/*

* for 10 ms clock period @ PCLK with 4 bit divider = 1/2

* (default) and prescaler = 16. Should be 10390

* @33.25MHz and 15625 @ 50 MHz

*/

timer_load_val = get_PCLK() / (2 * 16 * 100);

}

-------这个公式中的 2就是4 bit divider = 1/2，16就是prescaler = 16，100因为我们要的是10ms，所以要除100

/* load value for 10 ms timeout */

lastdec = timers->TCNTB4 = timer_load_val;

/* auto load, manual update of Timer 4 */

timers->TCON = (timers->TCON & ~0x00700000) | TCON_4_AUTO | TCON_4_UPDATE;

/* auto load, start Timer 4 */

timers->TCON = (timers->TCON & ~0x00700000) | TCON_4_AUTO | COUNT_4_ON;

timestamp = 0;



return (0);

这里有点不太明白，那就是为什么没有对下面这个寄存器进行操作：





}

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