[Intel-gfx] Sandy Bridge Desktop - 1920x1080i interlace not working

Daniel Vetter daniel at ffwll.ch
Thu Jan 19 12:32:19 CET 2012

On Thu, Jan 19, 2012 at 12:23:54PM +0100, Alfonso Fiore wrote:
> On Wed, Jan 18, 2012 at 9:12 PM, Daniel Vetter <daniel at ffwll.ch> wrote:
> > On Wed, Jan 18, 2012 at 05:08:55PM +0100, Alfonso Fiore wrote:
> >> would you agree that these are two separate bugs?
> >> I'd like the Intel driver to both:
> >> - allow me to use 1920x1080i
> >> - allow me to use 1024x768p without reverting to nomodeset
> >
> > Yep, that's correct. For the first issue Peter Ross is working on some
> > patches, for the later I suspect the missing CEA support. Please try this
> > out by grabbing the kernel tree I've told you and running it. Peter's
> > patches are on this mailing list, if it's easier for you I could create a
> > quick git branch somewhere.
> Ok Daniel, I also tested drm-intel-fixes branch (to check if I could
> get 1024x768p without flickering)
> I followed your instructions:
> - First checkout Keith's kernel tree:
> - git clone git://git.kernel.org/pub/scm/linux/kernel/git/keithp/linux.git
> - Then checkout the drm-intel-fixes branch with
> - git checkout -t origin/drm-intel-fixes
> - Confirm with
> - git branch
> - that you're indeed on the -fixes branch. Then do whatever your distor
> - howto tells you to compile a kernel from sources.
> after reboot I see yet an other behavior.
> LightDM shows an odd resolution. Not flickering but oddly placed and
> definitely not usable.
> After login the screen goes black (interestingly, not blue like when I
> try 1920x1080i)
> I logged in with VNC and tried to switch to 1024x768p with xrandr:
> xrandr --newmode "1024x768_01" 65.00  1024 1048 1184 1344  768 771 777
> 806 -hsync -vsync
> xrandr --addmode HDMI2 "1024x768_01"
> xrandr --output HDMI2 --mode "1024x768_01"
> but nothing changes.
> Recap: original kernel: two half screens flickering
> latest drm-intel-fixes branch: black screen
> attached dmesg.output and Xorg.0.log

It looks like we indeed detect more modes, unfortunately all the high-res
ones are interlaced. So you won't get anything new without Peter's
interlaced patches.

Also please don't add any modes with xrandr (or in your xorg.conf) and try
to reset any other xrandr tools that might change your mode when logging
in. It's rather likely that your TV is really picky about the mode, so if
you don't get it exactly right it'll bail out. xrandr should show you all
the detected (and by i915 supported modes).

Also, can you describe "oddly placed" more precisely (maybe with a pic)?

Yours, Daniel
Daniel Vetter
Mail: daniel at ffwll.ch
Mobile: +41 (0)79 365 57 48

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