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    drm/i915: hsw: fix link training for eDP on port-A · 3ab9c637
    Imre Deak 提交于
    According to BSpec the link training sequence for eDP on HSW port-A
    should be as follows:
    
    1. link training: clock recovery
    2. link training: equalization
    3. link training: set idle transmission mode
    4. display pipe enable
    5. link training: disable (set normal mode)
    
    Contrary to this at the moment we don't do step 3. and we do step 5.
    before step 4. Fix this by setting idle transmission mode for eDP at
    the end of intel_dp_complete_link_train and adding a new
    intel_dp_stop_link_training function to disable link training. With
    these changes we'll end up with the following functions corresponding
    to the above steps:
    
    intel_dp_start_link_train    -> step 1.
    intel_dp_complete_link_train -> step 2., step 3.
    intel_dp_stop_link_train     -> step 5.
    
    For port-A we'll call intel_dp_stop_link_train only after enabling the
    pipe, for everything else we'll call it right after
    intel_dp_complete_link_train to preserve the current behavior.
    
    Tested on HSW/HSW-ULT.
    
    In v2:
    - Due to a HW issue we must set idle transmission mode for port-A too
      before enabling the pipe. Thanks for Arthur Runyan for explaining
      this.
    - Update the patch subject to make it clear that it's an eDP fix, DP is
      not affected.
    
    v3:
    - rename intel_dp_link_train() to intel_dp_set_link_train(), use 'val'
      instead 'l' as var name. (Paulo)
    Signed-off-by: NImre Deak <imre.deak@intel.com>
    Reviewed-by: NPaulo Zanoni <paulo.r.zanoni@intel.com>
    Tested-by: NPaulo Zanoni <paulo.r.zanoni@intel.com>
    Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>
    3ab9c637
intel_ddi.c 41.3 KB