[Intel-gfx] [PATCH] drm/i915: Fix DDC bus selection for multifunction SDVO

[Eric Anholt]

On Tue, 04 May 2010 14:17:28 -0400, Adam Jackson <ajax at redhat.com> wrote:
> On Fri, 2010-04-23 at 16:16 -0400, Adam Jackson wrote:
> > Multifunction SDVO cards stopped working after 14571b4, and would report
> > something that looked remarkably like an ADD2 SPD ROM instead of EDID.
> > This appears to be because DDC bus selection was utterly horked by that
> > commit; controlled_output was no longer always a single bit, so
> > intel_sdvo_select_ddc_bus would pick bus 0, which is (unsurprisingly)
> > the SPD ROM bus, not a DDC bus.
> > 
> > So, instead of that, let's just use the DDC bus the child device table
> > tells us to use.  I'm guessing at the bitmask and shifting from VBIOS
> > dumps, but it can't possibly be worse.
> 
> Just to follow up on this, we're shipping the following two patches in
> F13 gold kernel:
> 
> http://cvs.fedoraproject.org/viewvc/rpms/kernel/F-13/drm-intel-sdvo-fix.patch?revision=1.1&content-type=text%2Fplain&view=co
> http://cvs.fedoraproject.org/viewvc/rpms/kernel/F-13/drm-intel-sdvo-fix-2.patch?revision=1.1&content-type=text%2Fplain&view=co
> 
> And, combined, they appear to fix DVI-I on at least one machine:
> 
> http://bugzilla.redhat.com/584229
> 
> I'm still skeptical of any approach that involves having to guess which
> DDC bus belongs to which connector.  The only thing that seems remotely
> sane to me is trusting the wiring table in the SDVO card itself.

Applied those two.

The fact that we're exposing 2 connectors for this situation is bogus in
how the KMS architecture is supposed to work, right?  I mean, we've got
2 "outputs" in this encoder going to one physical connector.  The user
should see one connector, and the encoder+connector should sort out how
to program the encoder for that situation.

Would having the same DDC bus for the child devs be a good enough
indication that we should have one SDVO encoder/connector for them and
they get to light up one SDVO encoder to the connector at a time? 
-------------- next part --------------
A non-text attachment was scrubbed...
Name: not available
Type: application/pgp-signature
Size: 197 bytes
Desc: not available
URL: <http://lists.freedesktop.org/archives/intel-gfx/attachments/20100507/b7311e95/attachment.sig>