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    SubjectRe: Radeon jittery post 2.6.35
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    On Tue, Mar 15, 2011 at 4:58 PM, Anders Eriksson <aeriksson@fastmail.fm> wrote:
    >  On 03/14/11 23:22, Alex Deucher wrote:
    >> On Mon, Mar 14, 2011 at 6:20 PM, Alex Deucher <alexdeucher@gmail.com> wrote:
    >> > On Sun, Mar 13, 2011 at 10:08 AM, Anders Eriksson <aeriksson@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

    EDID failure could very well explain it, EDID retrieval seems to fails
    on some GPU under some circonstance (when there is CPU load that
    interfer with i2c timing i guess). Does the log have the edid failure
    message when the tv is jittering ? Or is it the otherway around ?

    Cheers,
    Jerome
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