Re: Thunderbolt: One missing DisplayPort?

["Tomasz Moń" <desowin@gmail.com>]

On Mon, 2022-05-30 at 12:54 +0300, Mika Westerberg wrote:
> On Mon, May 30, 2022 at 10:33:06AM +0200, Tomasz Moń wrote:
> > On Sun, 2022-05-29 at 21:51 +0200, Stefan Hoffmeister wrote:
> > > I have managed to wedge the system into a state where it does not
> > > know about Thunderbolt, and now, on what I presume to be USB-C only
> > > ("usb_typec_revision" == 1.2? Seems ... low?), both DisplayPort
> > > outputs on the docking station are now active, and I do get
> > > meaningful entries from the DRM subsystem (and hence X). I am half-
> > > way happy: I want exactly that over Thunderbolt for the bandwidth ;)
> > 
> > Could you please tell how did you wedge the system into a state where
> > it does not know about Thunderbolt?
> > 
> > > Now, when I unwedge the system to enable Thunderbolt again
> > 
> > I am curious about the wedge/unwedge procedure.
> 
> Probably just connecting the dock using non-Thunderbolt Type-C cable.
> That will enter USB (+DP altmode) or so instead of Thunderbolt altmode.

How do I determine that the cable is non-Thunderbolt Type-C?

I have tried with two different brands 1m USB Type-C cables that are
not advertised as Thunderbolt. Both cables are electronically marked
and 5A capable. When the docking station is connected using these
cables, it operates in Thunderbolt mode.

If the device was operating in USB (+DP altmode), I assume that boltctl
would show that the docking station status as disconnected?

Can I read the cable EMCA details in Linux?

Best Regards,
Tomasz Moń