drm/i915/dp: optimize eDP 1.4+ link config fast and narrow
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:Rodrigo Vivi <rodrigo.vivi@intel.com> Reviewed-by:
Manasi Navare <manasi.d.navare@intel.com> Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=105267 Signed-off-by:
Jani Nikula <jani.nikula@intel.com> Link: https://patchwork.freedesktop.org/patch/msgid/20180905095321.13843-1-jani.nikula@intel.com
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