• Jani Nikula's avatar
    drm/i915/dp: optimize eDP 1.4+ link config fast and narrow · 7769db58
    Jani Nikula authored
    We've opted to use the maximum link rate and lane count for eDP panels,
    because typically the maximum supported configuration reported by the
    panel has matched the native resolution requirements of the panel, and
    optimizing the link has lead to problems.
    
    With eDP 1.4 rate select method and DSC features, this is decreasingly
    the case. There's a need to optimize the link parameters. Moreover,
    already eDP 1.3 states fast link with fewer lanes is preferred over the
    wide and slow. (Wide and slow should still be more reliable for longer
    cable lengths.)
    
    Additionally, there have been reports of panels failing on arbitrary
    link configurations, although arguably all configurations they claim to
    support should work.
    
    Optimize eDP 1.4+ link config fast and narrow.
    
    Side note: The implementation has a near duplicate of the link config
    function, with just the two inner for loops turned inside out. Perhaps
    there'd be a way to make this, say, more table driven to reduce the
    duplication, but seems like that would lead to duplication in the table
    generation. We'll also have to see how the link config optimization for
    DSC turns out.
    
    Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
    Cc: Manasi Navare <manasi.d.navare@intel.com>
    Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
    Cc: Matt Atwood <matthew.s.atwood@intel.com>
    Cc: "Lee, Shawn C" <shawn.c.lee@intel.com>
    Acked-by: default avatarRodrigo Vivi <rodrigo.vivi@intel.com>
    Reviewed-by: default avatarManasi Navare <manasi.d.navare@intel.com>
    Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=105267Signed-off-by: default avatarJani Nikula <jani.nikula@intel.com>
    Link: https://patchwork.freedesktop.org/patch/msgid/20180905095321.13843-1-jani.nikula@intel.com
    7769db58
intel_dp.c 187 KB