ARM移植之BootLoader(4)

作者：時(shí)間：2016-11-10 來(lái)源：網(wǎng)絡(luò)

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4. BootLoader第二階段

　　vivi Bootloader的第二階段又分成了八個(gè)小階段，在main函數(shù)中分別調(diào)用這幾個(gè)小階段的相關(guān)函數(shù)：

int main(int argc, char *argv[])
{
int ret;

/*
* Step 1:
*/
putstr("rn");
putstr(vivi_banner);

reset_handler();

/*
* Step 2:
*/
ret = board_init();
if (ret) {
putstr("Failed a board_init() procedurern");
error();
}

/*
* Step 3:
*/
mem_map_init();
mmu_init();
putstr("Succeed memory mapping.rn");

/*
* Now, vivi is running on the ram. MMU is enabled.
*/

/*
* Step 4:
*/
/* initialize the heap area*/
ret = heap_init();
if (ret) {
putstr("Failed initailizing heap regionrn");
error();
}

/* Step 5:
*/
ret = mtd_dev_init();

/* Step 6:
*/
init_priv_data();

/* Step 7:
*/
misc();

init_builtin_cmds();

/* Step 8:
*/
boot_or_vivi();

return 0;
}

　　STEP1的putstr(vivi_banner)語(yǔ)句在串口輸出一段字符說(shuō)明vivi的版本、作者等信息，vivi_banner定義為：

const char *vivi_banner =
"VIVI version " VIVI_RELEASE " (" VIVI_COMPILE_BY "@"
VIVI_COMPILE_HOST ") (" VIVI_COMPILER ") " UTS_VERSION "rn";

　　reset_handler進(jìn)行相應(yīng)的復(fù)位處理：

void
reset_handler(void)
{
　int pressed;

　pressed = is_pressed_pw_btn();

　if (pressed == PWBT_PRESS_LEVEL) {
　　DPRINTK("HARD RESETrn");
　　hard_reset_handle();
　} else {
　　DPRINTK("SOFT RESETrn");
　　soft_reset_handle();
　}
}

　　hard_reset_handle會(huì)clear內(nèi)存，而軟件復(fù)位處理則什么都不做：

static void
hard_reset_handle(void)
{
　clear_mem((unsigned long)USER_RAM_BASE, (unsigned long)USER_RAM_SIZE);
}

　　STEP2進(jìn)行板初始化，設(shè)置時(shí)間和可編程I/O口：

int board_init(void)
{
　init_time();
　set_gpios();

　return 0;
}

　　STEP3進(jìn)行內(nèi)存映射及MMU初始化：

void mem_map_init(void)
{
　#ifdef CONFIG_S3C2410_NAND_BOOT
　　mem_map_nand_boot();
　#else
　　mem_map_nor();
　#endif
　cache_clean_invalidate();
　tlb_invalidate();
}

　　S3C2410A的MMU初始化只需要調(diào)用通用的arm920 MMU初始化函數(shù)：

static inline void arm920_setup(void)
{
unsigned long ttb = MMU_TABLE_BASE;

__asm__(
/* Invalidate caches */
"mov r0, #0n"
"mcr p15, 0, r0, c7, c7, 0n" /* invalidate I,D caches on v4 */
"mcr p15, 0, r0, c7, c10, 4n" /* drain write buffer on v4 */
"mcr p15, 0, r0, c8, c7, 0n" /* invalidate I,D TLBs on v4 */
/* Load page table pointer */
"mov r4, %0n"
"mcr p15, 0, r4, c2, c0, 0n" /* load page table pointer */
/* Write domain id (cp15_r3) */
"mvn r0, #0n" /* Domains 0, 1 = client */
"mcr p15, 0, r0, c3, c0, 0n" /* load domain access register */
/* Set control register v4 */
"mrc p15, 0, r0, c1, c0, 0n" /* get control register v4 */
/* Clear out unwanted bits (then put them in if we need them) */
/* .RVI ..RS B... .CAM */
"bic r0, r0, #0x3000n" /* ..11 .... .... .... */
"bic r0, r0, #0x0300n" /* .... ..11 .... .... */
"bic r0, r0, #0x0087n" /* .... .... 1... .111 */
/* Turn on what we want */
/* Fault checking enabled */
"orr r0, r0, #0x0002n" /* .... .... .... ..1. */
#ifdef CONFIG_CPU_D_CACHE_ON
"orr r0, r0, #0x0004n" /* .... .... .... .1.. */
#endif
#ifdef CONFIG_CPU_I_CACHE_ON
"orr r0, r0, #0x1000n" /* ...1 .... .... .... */
#endif
/* MMU enabled */
"orr r0, r0, #0x0001n" /* .... .... .... ...1 */
"mcr p15, 0, r0, c1, c0, 0n" /* write control register */
: /* no outputs */
: "r" (ttb) );
}

　　STEP4設(shè)置堆棧；STEP5進(jìn)行mtd設(shè)備的初始化，記錄MTD分區(qū)信息；STEP6設(shè)置私有數(shù)據(jù)；STEP7初始化內(nèi)建命令。

　　STEP8啟動(dòng)一個(gè)SHELL，等待用戶(hù)輸出命令并進(jìn)行相應(yīng)處理。在SHELL退出的情況下，啟動(dòng)操作系統(tǒng)：

#define DEFAULT_BOOT_DELAY 0x30000000
void boot_or_vivi(void)
{
char c;
int ret;
ulong boot_delay;

boot_delay = get_param_value("boot_delay", &ret);
if (ret) boot_delay = DEFAULT_BOOT_DELAY;
/* If a value of boot_delay is zero,
* unconditionally call vivi shell */
if (boot_delay == 0) vivi_shell();

/*
* wait for a keystroke (or a button press if you want.)
*/
printk("Press Return to start the LINUX now, any other key for vivin");
c = awaitkey(boot_delay, NULL);
if (((c != r) && (c != n) && (c !=

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ARM移植之BootLoader(4)