Asus T100TA: USB boot fails from detachable keyboard USB port or SATA bay

[Illen]

Can't boot from USB port on detachable keyboard or the internal SATA bay (which uses an USB SATA adapter) on Asus T100TA. Booting from the microUSB port on tablet appears to work, and USB devices on detachable keyboard (keyboard/touchpad input, USB port and SATA adapter) are all working after system boots. Also internal USB read-only storage for recovery appears to be recognized during boot, apart from the microUSB port.

When switching the USB controller mode to EHCI, none of the USB devices (on keyboard or even tablet itself) work and it's not possible to boot at all. Since I can't obtain syslog from failed boot attempts and I don't have keyboard input during boot, I will attach the videos (for xHCI and for EHCI) of screen debug output and syslog from successful microUSB port boot.

Used haiku-master-hrev56578-x86_gcc2h.

xHCI USB Controller:

device Serial bus controller (USB controller, XHCI) [c|3|30]
  vendor 8086: Intel Corporation
  device 0f35: Atom Processor Z36xxx/Z37xxx, Celeron N2000 Series USB xHCI

USB devices:

/dev/bus/usb/0/0 - internal USB read-only recovery storage

/dev/bus/usb/0/1 - USB drive on microUSB port on the tablet (where USB boot works)

/dev/bus/usb/0/2 - Detachable keyboard connected through proprietary connector

/dev/bus/usb/0/3/0 - USB drive on detachable keyboard USB port (where USB boot doesn't work)

/dev/bus/usb/0/3/1 - USB SATA adapter in detachable keyboard (where USB boot doesn't work)

[waddlesplash]

When switching the USB controller mode to EHCI, none of the USB devices (on keyboard or even tablet itself) work and it's not possible to boot at all.

As long as XHCI mode works, what is the value of EHCI mode, anyway?

[Illen]

Replying to waddlesplash:

As long as XHCI mode works, what is the value of EHCI mode, anyway?

I tried EHCI mode to see whether it can workaround the USB boot problem on keyboard port. I mentioned it because I thought EHCI mode ideally shouldn't be broken either since it works fine on Linux or Windows.