Re: [Freedreno] [PATCH] drm/msm/dp: move add fail safe mode to dp_connector_get_mode()

From: Doug Anderson
Date: Tue Apr 26 2022 - 14:48:30 EST


On Tue, Apr 26, 2022 at 8:37 AM Abhinav Kumar <quic_abhinavk@xxxxxxxxxxx> wrote:
> > Can you provide the exact EDID from the failing test case? Maybe that
> > will help shed some light on what's going on. I looked at the original
> > commit and it just referred to, which I assume is "EDID Read
> > upon HPD Plug Event", but that doesn't give details that seem relevant
> > to the discussion here.
> Yes so it is and
> That alone wont give the full picture.
> So its a combination of things.
> While running the test, the test equipment published only one mode.
> But we could not support that mode because of 2 lanes.
> Equipment did not add 640x480 to the list of modes.
> DRM fwk will also not add it because count_modes is not 0 ( there was
> one mode ).
> So we ended up making these changes.

Ah! This is useful context and makes tons of sense.

This really feels like something that could be handled in the core. OK, See:

> > I guess maybe what's happening is that the test case is giving an EDID
> > where all the modes are not supportable by the current clock rate /
> > lanes? ...and then somehow we're not falling back to 640x480. It's
> > always possible that this is a userspace problem.
> >
> > In any case, would you object to a revert of the patches in the short term?
> Not sure, if you saw this change kuogee posted last night.
> We did decided to remove all the code related to these test cases and
> handle them in IGT.

I hadn't seen it yet and I wasn't CCed. :( I'll take a look now.