i830 modesetting adventure debriefing

Keith Packard keithp at keithp.com
Tue May 1 20:09:39 PDT 2007

On Tue, 2007-05-01 at 21:58 -0400, Kristian Høgsberg wrote:
> The ivch is online and the attached patch sets it up
> correctly.


> 1 - I don't see any way to get panel timings.

I'll see if we can't get i830 BIOS source code from somewhere to see
what the GPIO values are supposed to mean. Probably machine-dependent,
but you never know.

> 2 - The load detection code always returns true. 

That's very odd. Is the detection more stable when the VGA *is*

> Just for the record, I did get dual head working with VGA and DVO at
> some point.  I just jammed the n, m1, m2 values the BIOS used into
> FPA0 (I think that's what I did...) so I know the chipset can do it.

So that was two different CRTCs? Or the same CRTC driving both outputs?

> How different are the 845 and 855 chipsets?  Are they similar to 830
> and do they also use ivch?  Are 810 and 815 supposed to work?

845 and 855 are nearly identical, except the mobile verision has
built-in LVDS support, so the 830 stands alone in needing the ivch chip.
Everything else should be the same.

> Anyway, the ivch setup patch attached should be fine, I think.  I'll
> try to look into the pipe setup a little bit, but I don't know much
> about that code.

We've tried to make the code less fragile, but there are a lot of mystic
interdependencies that aren't well understood or documented.

keith.packard at intel.com
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