On Wed, Feb 27, 2019 at 01:16:27PM +0200, Jani Nikula wrote:
On Wed, 27 Feb 2019, Heikki Krogerus heikki.krogerus@linux.intel.com wrote:
One thing that this series does not consider is the DP lane count problem. The GPU drivers (i915 in this case) does not know is four, two or one DP lanes in use.
Also, orientation.
I guess that is not a critical issue since there is a workaround (I think) where the driver basically does trial and error, but ideally we should be able to tell i915 also the pin assignment that was negotiated with the partner device so it knows the DP lane count.
Yeah, if the information is there, we'd like to know. With the orientation, there's a worst case of sixth attempt of finding out there's just one lane in a certain orientation. Couple that with link rate selection (did it not work because too high link rate or because the lanes are just not there?) we get pretty confused about what we should try.
The orientation is also considered in the alt mode API. We have a function for that typec_altmode_get_orientation(), but it of course requires that the caller has a handle to the alt mode object. So basically we would again need tight coupling between the DP connector and USB Type-C connector.
Hans, I'm not so sure we should, or can, rule out the "tight coupling" option after all.
thanks,