• Daniel Vetter's avatar
    drm/i915: fixup interlaced vertical timings confusion, part 1 · ca9bfa7e
    Daniel Vetter authored
    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.
    Reviewed-by: default avatarEugeni Dodonov <eugeni.dodonov@intel.com>
    Reviewed-by: default avatarPaulo Zanoni <paulo.r.zanoni@intel.com>
    Tested-by: default avatarPaulo Zanoni <paulo.r.zanoni@intel.com>
    Tested-by: default avatarChristopher Egert <cme3000@gmail.com>
    Tested-by: default avatarAlfonso Fiore <alfonso.fiore@gmail.com>
    Signed-Off-by: default avatarDaniel Vetter <daniel.vetter@ffwll.ch>
    ca9bfa7e
intel_display.c 251 KB