[Intel-gfx] [PATCH] drm/i915: always set FDI composite sync bit

[Jesse Barnes]

On Tue, 11 Oct 2011 10:10:24 -0400
Adam Jackson <ajax at redhat.com> wrote:

> On 10/10/11 7:22 PM, Keith Packard wrote:
> > On Mon, 10 Oct 2011 14:28:52 -0700, Jesse Barnes<jbarnes at virtuousgeek.org>  wrote:
> >
> >> It's needed for 3 pipe support as well as just regular functionality
> >> (e.g. DisplayPort).
> >
> > Any explanation on how you get sync without this? As in, why did this
> > ever work?
> 
> To a first approximation, it didn't.  I was never able to get anything 
> reliably lit up besides the boot output (and only that one; hotplug 
> after was a disaster).
> 
> I don't have register dumps handy to compare BIOS setup with this 
> change, but I could if needed.
> 
> It still seems entirely magical and probably wrong in some situations. 
> And I'm thrilled to see that PPT is functionally different from CPT 
> (seriously, stop doing that) instead of just moving bit definitions 
> around (seriously, stop doing that).  But this change is massively 
> better than before.

Ok just got confirmation that always setting the composite bit is safe
on IVB per the specs we provide to board designers (i.e. they're
required to make composite sync work, and fsync/lsync is optional).

-- 
Jesse Barnes, Intel Open Source Technology Center
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