Re: State of USB-C PD on the linux kernel

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On Tue, Oct 31, 2017 at 04:19:58PM +0100, L. Rose wrote:
> Hi, thanks for your reply!
> 
> 
> On 31.10.2017 10:17, Heikki Krogerus wrote:
> > Hi,
> > 
> > It is likely that your system handles USB PD in firmware, and the OS
> > has no say in that. Which board is it?
> It's a "Gigabyte Z170X Ultra Gaming", which I (obviously) don't use for
> gaming ;)

OK. That board has the Thunderbolt3 controller. USB PD in it is handled
AFAIK by TI's USB PD controller in case you are interested. There is a
small (very small) chance that it is attached to the chipset's I2C host
instead of the EC.

Could you send acpidump to me?

> > You should be able to see the USB Type-C ports under
> > "/sys/class/typec" if your board supplies some kind of an interface
> > for the OS to them.
> > 
> >          % ls /sys/class/typec
> Unfortunately, the directory typec doesn't exist in /sys/class.
> > To check if your system supports UCSI:
> > 
> >          % cat /sys/bus/acpi/devices/USBC000\:00/status
> >          15
> The device doesn't exist, either.
> > If you don't have the device (/sys/bus/acpi/devices/USBC000\:00), or
> > if the status reads 0 instead of 15, UCSI is not supported in your
> > system.
> What does that mean, UCSI is not supported? Is that something that might be
> fixed somehow, or do I have to live with that?

There is really nothing that can be done. The BIOS does not supply the
interface, and that's it unfortunately. But everything will work in
any case. As said, everything will will be handled in firmware and
there is no need for software support. The ports are just not visible
to the OS.

I think Microsoft has now said (I'm _not_ 100% sure) that the USB
Type-C ports can not be hidden like that any more, and they should
always be visible to the OS, so the latest boards most likely will
always supply some kind of an interface to them. Either via BIOS
(UCSI) if EC in in control of them, or alternatively the OS will have
direct access to the USB PD controller or the USB Type-C PHY.


Cheers,

-- 
heikki
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