[Intel-gfx] [PATCH 12/13] drm/i915: clean up pipe bpp confusion

[Daniel Vetter]

On Wed, Mar 27, 2013 at 04:13:13PM -0700, Jesse Barnes wrote:
> On Wed, 27 Mar 2013 23:41:55 +0100
> Daniel Vetter <daniel.vetter at ffwll.ch> wrote:
> 
> > On Wed, Mar 27, 2013 at 10:28 PM, Jesse Barnes <jbarnes at virtuousgeek.org> wrote:
> > > I had to double check this against 9/13... I guess the order will be
> > > clearer with the actual code as opposed to patches.
> > >
> > > But won't these override the pipe_config bpp we set in
> > > pipe_config_set_bpp()?  Why bother setting it there if each of the
> > > encoders will set it themselves, and the real comparison is against
> > > the plane bpp?  And doesn't that mean we'd need to set pipe_config->bpp
> > > in the DP version too?
> > 
> > The pipe_bpp we set from the planes is the proposed one, used when
> > nothing else overrides it. Then encoders can come around and add in
> > their opinion about what's possible. Note that encoders want to know
> > which pipe_bpp is the proposed one (from looking just at the plane) to
> > make their own decision. E.g. hdmi wants to updither 10bpc to 12bpc
> > (if possible) since it doesn't support 10bpc natively. Whereas DP only
> > ever down-dithers.
> > 
> > This way we gain a notch more flexibility in handling bpp.
> > 
> > My auto-fdi dither work which is based on top of this goes one step
> > further and checks (after plane/pipe/encoder all had their say)
> > whether it actually fits into the fdi link. If it doesn't fit it tries
> > to dither down. If that's possible we'll restart the pipe_config
> > arbitrage, but with the new proposed pipe_bpp plus a flag telling
> > everyone that they'll get shot if they try to increase bw
> > requirements.
> > 
> > > Maybe I've been looking at this too hard and I've just confused
> > > myself...
> > 
> > Maybe it's a bit overdesigned ;-)
> 
> Ok it makes some sense... though maybe if we passed down the plane bpp
> directly we'd be able to avoid some of the re-calc stuff in your FDI
> dither patch.
> 
> We can always improve it after it lands and becomes clearer.
> 
> Reviewed-by: Jesse Barnes <jbarnes at virtuousgeek.org>

Slurped them all into dinq, thanks for the review.
-Daniel
-- 
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch