[Intel-gfx] [PATCH 2/8] drm/i915: fixup interlaced vertical timings confusion, part 1

[Eugeni Dodonov]

On Sat, Jan 28, 2012 at 11:49, Daniel Vetter <daniel.vetter at ffwll.ch> wrote:

> We have a pretty decent confusion about vertical timings of interlaced
> modes. Peter Ross has written a patch that makes interlace modes work
> on a lot more platforms/output combinations by doubling the vertical
> timings.
>
> The issue with that patch is that core drm _does_ support specifying
> whether we want these vertical timings in fields or frames, we just
> haven't managed to consistently use this facility. The relavant
> function is drm_mode_set_crtcinfo, which fills in the crtc timing
> information.
>
> The first thing to note is that the drm core keeps interlaced modes in
> frames, but displays modelines in fields. So when the crtc modeset
> helper copies over the mode into adjusted_mode it will already contain
> vertical timings in half-frames. The result is that the fixup code in
> intel_crtc_mode_fixup doesn't actually do anything (in most cases at
> least).
>
> Now gen3+ natively supports interlaced modes and wants the vertical
> timings in frames. Which is what sdvo already fixes up, at least under
> some conditions.
>
> There are a few other place that demand vertical timings in fields
> but never actually deal with interlaced modes, so use frame timings
> for consistency, too. These are:
> - lvds panel,
> - dvo encoders - dvo is the only way gen2 could support interlaced
>  mode, but currently we don't support any encoders that do.
> - tv out - despite that the tv dac sends out an interlaced signal it
>  expects a progressive mode pipe configuration.
> All these encoders enforce progressive modes by resetting
> interlace_allowed.
>
> Hence we always want crtc vertical timings in frames. Enforce this in
> our crtc mode_fixup function and rip out any redudant timing
> computations from the encoders' mode_fixup function.
>
> v2-4: Adjust the vertical timings a bit.
>
> v5: Split out the 'subtract-one for interlaced' fixes.
>
> v6: Clarify issues around tv-out and gen2.
>
> Signed-Off-by: Daniel Vetter <daniel.vetter at ffwll.ch>
>

Reviewed-by: Eugeni Dodonov <eugeni.dodonov at intel.com>

-- 
Eugeni Dodonov
<http://eugeni.dodonov.net/>
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