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Ville Syrjälä authored
Lots of machines these days seem to have a crappy type1 DP dual mode adaptor chip slapped onto the motherboard. Based on the DP dual mode spec we currently limit those to 165MHz max TMDS clock. Windows OTOH ignores DP dual mode adaptors when the VBT indicates that the port is not actually DP++, so we can perhaps assume that the vendors did intend that the 165MHz clock limit doesn't apply here. Though it would be much nicer if they actually declared an explicit limit through VBT, but that doesn't seem to be happening either. So in order to match Windows behaviour let's ignore the DP dual mode adaptor's TMDS clock limit for ports that don't look like DP++ in VBT. Unfortunately many older VBTs misdelcare their DP++ ports as just HDMI (eg. ILK Dell Latitude E5410) or DP (eg. SNB Lenovo ThinkPad X220). So we can't really do this universally without risking black screens. I suppose a sensible cutoff is HSW+ since that's when 4k became a thing and one might assume that the machines have been tested to work with higher TMDS clock rates. v2: s/IS_BROADWELL/IS_HASWELL/ Acked-by: Jani Nikula <jani.nikula@intel.com> Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com> Link: https://patchwork.freedesktop.org/patch/msgid/20211222161738.12478-1-ville.syrjala@linux.intel.com
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