ARM移植之BootLoader(4)
加入技術(shù)交流群
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 != |