Radeon jittery post 2.6.35

[Anders Eriksson]

 On 03/14/11 23:22, Alex Deucher wrote:
> On Mon, Mar 14, 2011 at 6:20 PM, Alex Deucher <alexdeucher at gmail.com> wrote:
> > On Sun, Mar 13, 2011 at 10:08 AM, Anders Eriksson <aeriksson at fastmail.fm> wrote:
> >>  Hi,
> >>
> >> I've found what I guess is a radeon (or drm/kms) regression post 2.6.35.
> >> I've got my TV conneced to my RS690G over HDMI, and the display has
> >> always been jittery after POST and at the GRUB screen. Pre-KMS, the X
> >> server (or driver got it sorted), and when KMS started, the display
> >> stabilized right after the kernel driver was initiated. However, post
> >> 2.6.35, I see the jitter is back.
> >>
> >> I've spent the last month trying to bisect it, but pretty much failed.
> >> It appears that versions closer to 2.6.38-rcX are more prone to display
> >> jitter, while 2.6.36 or so can have many successful runs. It also
> >> appears to be related to device power-on order, or so I've come to
> >> believe; A stable display can turn jittery, just by power cycling the TV.
> >>

Some further testing on a clean rc8 suggests that the jitter seen
there can  reliably be removed by power cycling the TV while in X,
or starting X with the TV off.

I'm tempted to think that something makes too much out of bad
info collected from the TV, and falls backs to saner defaults if
the TV has nothing to say.

I've seen in the logs that the EDID is disliked:
[drm:radeon_dvi_detect] *ERROR* HDMI-A-1: probed a monitor but
no|invalid EDID
Not sure if that is related though (cannot seem to be able to provoke
that error message right now)

-A