Re: [Qemu-devel] OVMF, Q35 and USB keyboard/mouse

[Laszlo Ersek]

On 09/10/14 08:31, Gerd Hoffmann wrote:
>   Hi,
> 
>> So at this point I'm wondering why guests and "info qtree" are contradictory,
>> and whether the combination of OVMF and OS X tickle some qemu usb emulation
>> bug differently than all other (working) combinations ?
> 
> It's due to the way how usb1 compatibility was implemented when ehci was
> introduced ...
> 
> Each usb 2.0 port is linked to both uhci and ehci controller.  ehci
> controls the port routing (i.e. whenever a device shows up @ uhci or
> ehci).  There is one global bit and one per-port bit which control the
> routing.

Is "4.2.1 Port Routing Control via EHCI Configured (CF) Bit" related?
The Configured Flag (CF) is the global one apparently, and the Port
Owner bit is per port.

In "MdeModulePkg/Bus/Pci/EhciDxe/", the CF flag seems to be called
CONFIGFLAG_ROUTE_EHC, and Port Owner is PORTSC_OWNER.

> The global bit says whenever the ports should be routed to ehci by
> default or not.  EHCI driver software is supposed to flip that bit at
> initialization time to get all devices routed to ehci.  Power-on default
> is route everything to uhci, so if the OS knows nothing about ehci all
> usb devices will show up on the uhci companion.
> 
> The per-port bit should be flipped by the ehci driver for usb1 devices,
> so they are handed over to uhci as ehci supports usb2 devices only.
> 
> 
> In qemu this is implemented by having ehci managing the usb bus and uhci
> registering its ports as companion ports.  ehci emulation will either
> handle the devices itself or call uhci, depending on how the guest has
> configured the routing.
> 
> There is even a basic test case for that:  tests/usb-hcd-ehci-test.c
> 
> Because ehci manages the bus the usb devices show up on ehci in 'info
> qtree', no matter how the port routing is configured.
> 
>> Not sure how I'd force the keyboard and mouse onto the default uhci1 and/or
>> uhci2 (from the qtree perspective), since they're given empty IDs by default
>> (and my qemu command line kung-fu is weak in this area).
> 
> Pure uhci working fine hints it most likely is a bug somewhere in the
> port routing code.  Could be in ovmf, but could be qemu too.  You can't
> force it from outsize, port routing is guest business.
> 
> What happens if you build ovmf with uhci but without ehci driver?  Does
> that work?

I'm glad I happened to suggest the same. ;)

Laszlo