How to Reboot/Re-Enable Watchdog on Libre Computer AML-S905X-CC Le Potato?

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1

I am running Raspbian Bullseye and cannot make the device reboot under any circumstance:

reboot
shutdown -r -f now
echo b > /proc/sysrq-trigger

All of these result in the system halted with the red power light on.

Can the watchdog be re-enabled? If so:

  1. What needs to be echoed into /dev/watchdog?
  2. Which bootloader can be used with flashtool to make the change permanent?

Thanks!

2

Update:

This only happens when OTG USB is connected to another USB host, regardless if c9100000.usb is in host or device mode. The board is pulling power from the USB-connected host. Even if I unplug the main power the AML board power stays lit and does not reboot when main power is reapplied. Is it possible to disable power to/from c9100000.usb? Will re-enabling watchdog matter?

Being able to reboot even when in OTG mode is pretty important.

3

Update #2: I taped over the power and ground pins on usb cable which means I can now shutdown by only pulling main power but now device will not boot at all while cable is inserted. If I insert doctored cable after boot, it works great as OTG client to host system.

With a standard USB plugged into this port the device reboots normally.

4

After disconnecting/reconnecting everything and a cold-boot, the device seems to be rebooting normally now in OTG mode as long as I use the USB cable with the power leads taped over.

Solution to my problem:

  1. apt install watchdog
  2. tape over power/ground inside usb connection of cable plugged into OTG port
5

If there is reverse power going to the 5V on USB, the system tries to reset by turning off the regulators. However, it’s unable to reset the chip because the 5V is on when it should be off. Watchdog is the only way.

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6

Thank you, I got there.

This information should go into a FAQ for anyone wanting to use OTG function.

7

Added a note to it on the OTG function. Thanks for your input.

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