Intel i915GM with SDVO CH7021A support?

Eric Anholt eric at
Mon Nov 13 13:51:06 PST 2006

On Mon, 2006-11-13 at 15:28 +0000, will wrote:
> Hi,
> A few months ago I got a version of the mode setting Intel 915 driver from a
> git tree posted on airlied's live journal. With a bit of fiddling and
> tweaking this has been working very well and I can get very close to the
> refresh rates required for video etc.
> I've had no success with the CH7021A SDVO support under linux at all.
> Chrontel refuse to supply any details about how to program the chip. I did
> manage to get the DVI working with the IEGD binary driver but it wouldn't
> recognise or work the CH7021A at all. I'd really like to get the CH7021A
> working as it supports HDTV, SCART out and exact TV refresh rates and spec
> etc etc. Without proper support it's impossible to adjust the internal
> parameters as it is with the Windows driver.
> If any one has any suggestion or can help me it would be appreciated. I'm
> quite happy to try any experimental code or hack something together if there
> is a bit of detail about how to get the 7021 to respond available. I
> understand it may be possible to snoop the I2C bus and potentially work out
> what is going on with the SDVO. Would this be a viable method or would I
> just be wasting my time trying? I should probably know the answer to this
> but it would help if someone could confirm this... Once the PC has booted up
> is it possible to switch the SDVO 7021A TV out on using a BIOS call, I had a
> brief look in the VESA spec but I could easily have missed this. Presumably
> if a BIOS call is available presumably the snooping method will work...
> otherwise would it be possible / practical to snoop the I2C bus at bootup
> using some sort of TSR when the TV Out is enabled?
> Thanks for any help anyone can provide

You're probably going to have minimal luck trying to get the BIOS to do
anything special.  While we haven't done any TV development in the
modesetting branch of xf86-video-intel git, it has the continuation of
the work that airlied started, and I'd love to help integrate any
appropriate code for TV support.  If you can get the master branch to
turn your TV on at all, you may be able to use the BIOS tracing tools
that are floating around to figure out what the BIOS is doing and
replicate it.

Unfortunately, I don't think I'll have any time to work on SDVO TV
support directly any time soon.

Eric Anholt                             anholt at
eric at                         eric.anholt at
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