如何在Android user 版本下打开UART log

如果为了调试
1. 打开一个文件:
alps/mediatek/config/common/autoconfig/kconfig/USER
查看是否存在CONFIG_COMLINE=”console=ttyMT3,921600n1 loglevel=0”，如果存在，则把loglevel=0修改为loglevel = 8
然后
./mk n k
./mk bootimage

2. 如不存在CONFIG_COMMLINE，则查看alps/bootable/bootloader/lk/app/mt_boot/mt_boot.c的boot_linux()函数：
if (!has_set_p2u) {
#ifdef USER_BUILD
sprintf(cmdline,"%s%s",cmdline," printk.disable_uart=1");
#else
sprintf(cmdline,"%s%s",cmdline," printk.disable_uart=0");
#endif
}
修改为：
if (!has_set_p2u) {
#ifdef USER_BUILD
sprintf(cmdline,"%s%s",cmdline," printk.disable_uart=0 ignore_loglevel");
#else
sprintf(cmdline,"%s%s",cmdline," printk.disable_uart=0");
#endif
}