I tested all 4 methods in this article. But I still cannot get into download mode.
The second method get me into a factory mode:
SECOND METHOD
- Power phone off
- Plug USB into Computer
- Plug microUSB into phone
- Hold pwr + vol up + vol down
- When Batt icon goes away, release pwr, still holding vol up + vol down
- Yellow /_\ (triangle, Downloading, Andy shoveling, Do not turn off Target!!! symbol)
You should now be in Download mode.
Edit:
turns out there is no such mode. The adb shell default is root shell. To root the device, I can simply adb pull <system partition>
, then mount on PC to add su and other stuff, then just flash it back.