Unsynced TMDS with xf86-video-intel on 945GM

Keith Packard keithp at keithp.com
Wed May 16 12:36:22 PDT 2007

On Mon, 2007-05-14 at 09:18 +0200, René Rebe wrote:

> However often (like about 80% of the X starts) I get flickering and rolling thru
> pixel trash on the external display. It "looks" like there is some sync (or so)
> missing or imprecise, as it's the actual desktop pixel content flushing and
> shuffling by.

> This can be fixed by re-enabling the LVDS and disabling it again:

Sounds like the mode programming has some stability issues; the
registers in the chip must be programmed in the right sequence and with
the right delays between various steps in the process. Failing to wait
long enough for a PLL to lock can result in 'bad' behaviour like this.

About the only way to debug this is to add delays at various points in
the mode setting operation, most likely the CRTC timing programming,
although it's possible that the SDVO programming is broken instead.

One thing to always try is the latest development version of the X
server and intel driver; there are a few minor fixes which may be
related. Plus, patches you come up with won't need to be ported forward.

keith.packard at intel.com
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