02 ARM11 时钟初始化后的跑马灯程序

.text
.globl _start
_start:
        ldr r0, =0x70000000
        orr r0, r0, #0x13
        mcr p15, 0, r0, c15, c2, 4

        ldr r0, =0x7e004000
        mov r1, #0
        str r1, [r0]

        bl clock_init
        ldr sp, =8*1024
        bl xxxx

        b .

start.S 文件，调用完时钟初始化函数后调用跑马灯程序。

.globl clock_init
clock_init:
	ldr r0, =0x7E00F000
	ldr r1, =0x0000FFFF
	str r1, [r0]
	str r1, [r0, #4]
	str r1, [r0, #8]

#define OTHERS		0x7e00f900
	ldr r0, =OTHERS
	ldr r1, [r0]
	bic r1, r1, #0xc0
	str r1, [r0]

loop1:
	ldr r0, =OTHERS
	ldr r1, [r0]
	and r1, r1, #0xf00					
	cmp r1, #0
	bne loop1		

#define ARM_RATIO    0   /* ARMCLK = DOUTAPLL / (ARM_RATIO + 1)    */
#define HCLKX2_RATIO 1   /* HCLKX2 = HCLKX2IN / (HCLKX2_RATIO + 1) */
#define HCLK_RATIO   1   /* HCLK = HCLKX2 / (HCLK_RATIO + 1)       */
#define PCLK_RATIO   3   /* PCLK   = HCLKX2 / (PCLK_RATIO + 1)     */
#define MPLL_RATIO   0   /* DOUTMPLL = MOUTMPLL / (MPLL_RATIO + 1) */
	ldr r0, =0x7E00F020  /* CLK_DIV0 */
	ldr r1, =(ARM_RATIO) | (MPLL_RATIO << 4) | (HCLK_RATIO << 8) | (HCLKX2_RATIO << 9) | (PCLK_RATIO << 12)
	str r1, [r0]

#define APLL_CON_VAL  ((1<<31) | (266 << 16) | (3 << 8) | (1))
	ldr r0, =0x7E00F00C
	ldr r1, =APLL_CON_VAL
	str r1, [r0]

/*
 * APLL_CON, FOUTAPL = MDIV * Fin / (PDIV*2^SDIV) = 266*12/(3*2^1) = 532MHz
 */

#define MPLL_CON_VAL  ((1<<31) | (266 << 16) | (3 << 8) | (1))
	ldr r0, =0x7E00F010
	ldr r1, =MPLL_CON_VAL
	str r1, [r0]

/*
 * MPLL_CON, FOUTMPL = MDIV * Fin / (PDIV*2^SDIV) = 266*12/(3*2^1) = 532MHz 
 */
	ldr r0, =0x7E00F01C
	ldr r1, =0x03
	str r1, [r0]
	
	mov pc, lr 

clock.S：时钟初始化。

 

all:start.o clock.o led.o
        arm-linux-ld -Ttext 0 -o led.elf start.o clock.o led.o
        arm-linux-objcopy -O binary led.elf led.bin
        arm-linux-objdump -D led.elf > led.dis
        cp led.bin /tftpboot/led.bin
%.o:%.S
        arm-linux-gcc -c $< -o $@
%.o:%.c
        arm-linux-gcc -c -o $@ $<
clean:
        rm -rf *.o *.elf *.dis *.bin /tftpboot/*.bin

 

Makefile:在跑马灯的基础上添加clock.o

 

void delay ()
{
	int i;

	for (i = 0; i < 100000; i++)
		;
}

int xxxx (void)
{
	volatile unsigned long *gpmcon = (volatile unsigned long *)0x7f008820;		volatile unsigned long *gpmdat = (volatile unsigned long *)0x7f008824;
	int i;

	for (i = 1; i <= 4; i++){
		if (1 == i){
			*gpmcon &= ~0xffff;
			*gpmcon |= 0x1;
		}else if (2 == i){
			*gpmcon &= ~0xffff;
			*gpmcon |= 0x10;
		}else if (3 == i){
			*gpmcon &= ~0xffff;
			*gpmcon |= 0x100;
		}else if (4 == i){
			*gpmcon &= ~0xffff;
			*gpmcon |= 0x1000;
			i = 0;
		}
		*gpmdat = 0;
		delay();
	}

	return 0;
}

 

led.c：同上一章一样。

结果：初始化时钟后，跑马灯速度明显快于不初始化时钟的跑马灯程序。