On 04/02/15 01:20, Russell King - ARM Linux wrote:
This is where the DRM model is weak - we don't really have a way to say "this is the set of CRTCs which/can/ be associated with this connector, can any of the CRTCs accept this mode?" and eliminate modes which fail that check.
This problem seems to be one which recurrs, so I wonder if it's something which ought to be solved properly.
It's made slightly more difficult because we don't really know which connectors could be associated with which CRTCs - that information is stored at the encoder level (with the encoders possible_crtcs), and I'm not sure we have a way for generic DRM code to know which encoders could be associated with which connectors.
I agree that this is not the most elegant solution to the problem, but it works with Beaglebone-Black - which is AFAIK the only piece of HW that uses tda998x with tilcdc.
I would like to get these patches merged and revisit the mode validation code once we have a better solution for it.
Best regards, Jyri