Fix PinePhone Pro when unable to boot due to drained battery

[butjar]

I just wanted to share how I got my PPPro booting after the battery was fully drained (just after I received my phone). I saw there are already some Threads (e.g. #15896) which describe this issue. However, I wanted to share some additional debugging instructions for reference. These instructions will help ascertaining if the phone enters Maskrom mode correctly (precondition for charging the drained battery). The actual instructions that helped me solving my issue are described in the blue box of the Installation instructions in the PPPro wiki.


Behavior: The phone does not boot (neither does it charge)

Fix: Instructions how to charge the PPPro if the battery is fully drained (quoted from the wiki):

If the battery is fully drained U-Boot might fail to boot any installed operating system on the eMMC and microSD card due to a bug.
If that's the case please start your phone in Maskrom mode and let it charge in that for a few hours. To do that:

• Remove any microSD card from the phone
  
• Hold the "RE" button underneath the back cover of your Explorer Edition (or shorting the bypass contact points on the Developer Edition)
  
• Connect the phone to an USB port of a computer, while still holding the button
  
• Check if the phone in Maskrom mode appears in the output of the Linux command lsusb on the computer (if the device disappears again please use a different cable)
  
• Let the phone charge for multiple hours
  

Note: If that didn't work, try to remove the battery and the USB cable and hold the power button for a few seconds and then insert the battery again, before retrying the procedure.

In addition to these instructions, I observed the lsusb and dmesg outputs when connecting the PPPro to the USB port of my laptop. I opened two terminal windows:

1. In the first terminal window I watched the lsusb output, while connecting the PPPro with the RE button pressed. The device showed up on the USB bus:
   
   Code:

   $ watch lsusb
...
Bus 001 Device 011: ID 2207:330c
...
2. In a second terminal window I concurrently observed the dmesg output, while connecting the PPPro. Here, the PPPro was showing up on the USB port as well:
   
   Code:

   $ tail -f /var/log/{messages,kernel,dmesg,syslog}
...
Feb  2 13:19:15 <HOSTNAME> kernel: [148427.240994] usb 1-1.2: new high-speed USB device number 11 using ehci-pci
Feb  2 13:19:15 <HOSTNAME> kernel: [148427.350785] usb 1-1.2: New USB device found, idVendor=2207, idProduct=330c
Feb  2 13:19:15 <HOSTNAME> kernel: [148427.350791] usb 1-1.2: New USB device strings: Mfr=0, Product=0, SerialNumber=0
Feb  2 13:19:15 <HOSTNAME> mtp-probe: checking bus 1, device 11: "/sys/devices/pci0000:00/0000:00:1a.0/usb1/1-1/1-1.2"
Feb  2 13:19:15 <HOSTNAME> mtp-probe: bus: 1, device: 11 was not an MTP device
Feb  2 13:19:15 <HOSTNAME> upowerd[2113]: unhandled action 'bind' on /sys/devices/pci0000:00/0000:00:1a.0/usb1/1-1/1-1.2
...
   
   

After charging the phone for several hours (~2-3h), I was able to boot the PPPro. However, the phone was still almost drained. I finished the initial setup and re-plugged the phone into my USB charger and finally my PPPro is charging as expected.