Re: [PATCH] drm/i915: always set FDI composite sync bit

[Jesse Barnes <jbarnes@virtuousgeek.org>]

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On Tue, 11 Oct 2011 12:42:22 -0400
Adam Jackson <ajax@redhat.com> wrote:

> On 10/11/11 12:16 PM, Jesse Barnes wrote:
> > On Tue, 11 Oct 2011 10:10:24 -0400 Adam Jackson<ajax@redhat.com>  wrote:
> >> 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.
> >
> > Without composite sync, FDI needs frame/line sync (the fsync/lsync
> > mentioned in the docs), which means extra wires between the CPU and
> > PCH.  Some boards don't have these and so we need to use composite.
> > For the same reason, if FDI B and C are sharing lanes, we need to use
> > composite or we won't have enough lines to go around.
> >
> > I've asked the hardware guys whether using composite on a board that
> > supports fsync/lsync is ok generally; if so just defaulting to that
> > everywhere should be fine.
> 
> Makes sense.  If true this seems worth doing for CPT too.  The IBX docs 
> don't make any mention of composite sync.

Supposedly SNB doesn't support this on the CPU side, so I've only put
it in the IVB FDI training code.  ILK + IBX don't support it at all
according to the hw folks.

-- 
Jesse Barnes, Intel Open Source Technology Center

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