[coreboot] USB Support on Apollo Lake

Zeh, Werner werner.zeh at siemens.com
Mon Mar 20 12:48:24 CET 2017

Hi Gailu.

I don't think that one can configure the xHCI to behave like an EHCI so that GRUB2 can natively support it.
xHCI has different version number in the PCI space which will prevent the EHCI driver in GRUB2 to use this controller at all.
Not speaking about the complete different register set and operational model.

What in turn should work is that "some of the BIOS" (which in coreboot-context is the payload like SeaBIOS) will handle all the
xHCI stuff and provide a legacy interface to the OS (and here GRUB acts as an OS) to just read mass storage devices using interrupts.

Beside that you are lost with GRUB2 and xHCI, sorry!


>Hi Experts,
>Does coreboot support USB port initialization in legacy mode on Apollo Lake as some of the BIOS does so that grub or other payloads can use it as USB2.0?
>There is no USB2.0 port on this board and Grub2 doesn't support xhci so we seems to be reaching to a dead end.
>I am trying to see if the dual role USB ports can be initialized in coreboot/fsp so that they can act as USB2.0 for payloads.

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