get into fastboot mode without hard power cycle

[kejiahu]

Hi,

I am wondering if there is a way to get into fastboot mode without the need of unplug/plug the power lead? As we want to implement some kind of CI to test our development, thus remote and scriptable control is needed in our case.

I noticed long press PWR_ON button will make the board reboot, but it seems I can't get into fastboot mode even with VOL- pressed during rebooting. Not sure if any combination of pressing the PWR_ON and VOL- will achieve my goal.

Regards,
Kejia

[ashwin]

Hi,

If you are on android then you can use "adb reboot bootloader" command to get the board into fastboot mode without removing the power cable.

Best Regards,
Ashwin

[tamo2]

If you are using Linux, there is a "hack".
If there is no kernel in the boot partition, then it switches to fastboot mode. So, for example, from Linux console:
> sudo dd if=/dev/zero of=/dev/disk/by-partlabel/boot # clear boot partition.
> sudo reboot

Then it goes to fastboot. Since the kernel is erased, you need to flash kernel (which is easy because you are in fastboot mode).

[kejiahu]

thanks both for replying.

For our use case, we'd like to be able to get into fastboot mode without dependency on the userland, as we are supposed to build our own kernel, and there is no guarantee it can boot into userland each time. And also we'd like to involve some CI system, that's why we can't use non-scriptable method.

so if we have a kernel in the boot partition, but it crashes, what will happen? will it get into fastboot mode after a few attempts?

Regards

[tamo2]

so if we have a kernel in the boot partition, but it crashes, what will happen? will it get into fastboot mode after a few attempts?

Usually not. It just crashes.
At that point you would have to manually set it into fastboot, but how often can it happen?
BTW, fastboot can boot kernel without flashing to ufs. You may want to use that mode, then if something happens, then you just power cycle the system to back to fastboot.

The alternative is, to use some external equipment. We have used USB contollable power supply to power cycle a system from software. We have used one from Korad and it works great (we have also used PowerUSB but it didn't work because it didn't completely shutoff power).
You will also need some USB-GPIO to mimic pushing "VOL-" switch.

[kejiahu]

BTW, fastboot can boot kernel without flashing to ufs. You may want to use that mode, then if something happens, then you just power cycle the system to back to fastboot.

boot without flashing sounds a good idea, but it seems there is a problem with "fastboot boot <kernel>" command at moment, I got error:
FAILED (remote: bootimage: incomplete or not signed)
while same image boots if I flash it to ufs.

The alternative is, to use some external equipment. We have used USB contollable power supply to power cycle a system from software. We have used one from Korad and it works great (we have also used PowerUSB but it didn't work because it didn't completely shutoff power).
You will also need some USB-GPIO to mimic pushing "VOL-" switch.

We have some serial controllable PSUs, but this is the last route we'd like to go... As we have several dev boards which we want to keep them the same setup, to control power from PSU means the boards need dedicate PSU for each of them which is not ideal....

Anyway, thanks for the suggestions, and we will get it sorted