HDMI Scanlines & flicking when composite converter attached at boot.
I have a slackware 14 system with an i915 which has two HDMI outputs connected and it works perfectly, using xrandr to adjust resolutions and such once it gets in to X.
The issue appears when I change one of the HDMI connections to go through a HDMI to AV converter (composite + audio) and happens during startup. The basic process is this:
* Bios displays
* Lilo graphic displays
* Initial kernel text displays
* Starts udev, initiates graphics & switches to high resolution console
!!! Issue starts here, from now on the straight HDMI connection keeps flicking and readjusting, & the converted HDMI disappears !!!
* System keeps doing its loading until X
* X starts in correct resolution. Still no converted image, and straight HDMI still flicking madly with a "scanline" slowly revealing the picture from top to bottom. The "scanline" sometimes skips and reveals about half the screen quickly, and the flicking is very random in timing.
Audio does however work regardless.
Using nomodeset disables the intel driver and changes to slow rendering so that isn't an option. It does however let the converted display continue on as normal.
I can get the converted display to work if I leave it unplugged until sometime after the udev / initial scripts. If I plug it in then, it stays blank until X, which detects it and everything works and displays flawlessly. Also interesting to note is Ubuntu loads perfectly with no flicking. The only real difference I can see is a newer kernel (3.5 vs 3.2).
So I am guessing it is something to do with KMS which doesn't look like it can be avoided, or even possibly a handshake issue on the module loading, or maybe even audio causing havoc?
Any ideas are welcome!
A bit more testing.
Issue definitely occurs when udev & modprobe happen. Here is the output from dmesg for that period relevant to the video.
(ignore the times - I stuck an artificial 30s delay to narrow down the issue. normally happens around 5s.)
Edit: Here's the "clean" dmesg when two HDMI monitors are connected with no issues.
Edit #2: Even more info. Booting up clean (as directly above), then swapping an output straight to the converter produces no log messages whatsoever. But when X is restarted it still comes up with clean pictures as if nothing is wrong and logs the following:
The command where the issue happens is in rc.udev:
All sorted - decided to bite the bullet and build a more recent kernel (3.5.4) which solved the problem. Must have been something iffy in the 3.2 release.
Hopefully this helps someone out!
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