Re: [PATCH] drm/i915: implement high-bpc + pipeconf-dither support for g4x/vlv

["Ville Syrjälä" <ville.syrjala@linux.intel.com>]

On Wed, Apr 24, 2013 at 12:27:59AM +0200, Daniel Vetter wrote:
> On Tue, Apr 23, 2013 at 10:39:35PM +0200, Daniel Vetter wrote:
> > On Tue, Apr 23, 2013 at 06:27:54PM +0300, Ville Syrjälä wrote:
> > > The g4x docs are a bit confusing though. They seem to indicate the the
> > > PIPECONF dither controls only affect DP.
> > 
> > Hm, this could put a pending question from Jesse at ease whether we should
> > still enable dithering in the lvds port register on g4x. Can you point me
> > at the relevant bspec language? I didn't spot anything when hunting around
> > in the docs ...
> 
> Hm, I've done some testing and the pipeconf dithering seems to indeed have
> no effect on the lvds panel. I've gotten away since this patch didn't
> clear that bit correctly. I'll update the patch. If you can dig out the
> Bspec reference, that'd still be great.

It's mentioned in the PIPECONF description.

"4   | Dithering enable [DevCTG]: This bit enables dithering for DisplayPort 6bpc or 8bpc modes"
"3:2 | Dithering type [DevCTG]: This bit selects dithering type for DisplayPort 6bpc or 8bpc modes"

Also the description of "7:5 | Bits Per Color [DevCTG]" also talks a lot about
DP, which maybe implies that it too only affects DP. For SDVO/HDMI the
port register anyway only has 8bpc support so I guess that's covered, but
I'm not sure what the deal is with the CRT output.

-- 
Ville Syrjälä
Intel OTC