drm/i915/cnl: Force DDI_A_4_LANES when needed.
As we faced in BXT, on CNL DDI_A_4_LANES is not set as expected when system is boot with multiple monitors connected. This result in wrong lane setup impacting the max data rate available and consequently blocking modeset on eDP, resulting in a blank screen. Most of CNL SKUs don't support DDI-E. The only SKU that supports DDI-E is the same that supports the full A/E split called DDI-F. Also when DDI-F is used DDI-E cannot be used because they share Interrupts. So DDI-E is almost useless. Anyways let's consider this is possible and rely on VBT for that. This patch was initialy start by Clint, but required many changes including full commit message. So Credits entirely to Clint for finding this. v2: Extract all messy conditions into a helper function as suggested by Ville. Along with simplification I removed the debug message on the working case since now all conditions are grouped. v3: Split the conditions even more as suggested by Ville. Get's cleaner and easier to add new cases in the future. Suggested-by:Clint Taylor <clinton.a.taylor@intel.com> Cc: Clint Taylor <clinton.a.taylor@intel.com> Cc: Mika Kahola <mika.kahola@intel.com> Cc: Jani Nikula <jani.nikula@intel.com> Cc: Ville Syrjälä <ville.syrjala@linux.intel.com> Signed-off-by:
Rodrigo Vivi <rodrigo.vivi@intel.com> Reviewed-by:
Ville Syrjälä <ville.syrjala@linux.intel.com> Link: https://patchwork.freedesktop.org/patch/msgid/20171023173920.22890-1-rodrigo.vivi@intel.com
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