一、定位源碼

通過查看lowlevel_init.c中的函數(shù)do_lowlevel_init可知，電源管理函數(shù)名稱為set_ps_hold_ctrl。

通過查看power.c，可找到函數(shù)set_ps_hold_ctrl。

二、修改源碼

修改函數(shù)set_ps_hold_ctrl。

void set_ps_hold_ctrl(void)
{
    if (cpu_is_exynos5())
        exynos5_set_ps_hold_ctrl();

    if (cpu_is_exynos4())
        exynos4_set_ps_hold_ctrl();
}

在函數(shù)set_ps_hold_ctrl的上面增加新的函數(shù)

static void exynos4_set_ps_hold_ctrl(void)
{
    __asm__ __volatile__(
        "ldr     r0, =0x1002330C\n"
        "ldr     r1, =0x300\n"
        "str     r1, [r0]\n"
        
        "ldr     r0, =0x11000C08\n"
        "ldr     r1, [r0]\n"
        "bic     r1, r1, $0x30\n"
        "str     r1, [r0]\n"
        
        :
        :
        :"r0", "r1"
    );
}

電源芯片.png

GPIO.png