1. 06 Oct, 2021 1 commit
    • Ville Syrjälä's avatar
      drm/i915: Tweak the DP "max vswing reached?" condition · 8bc2f5c3
      Ville Syrjälä authored
      Currently we consider the max vswing reached when we transmit a
      the max voltage level, but we don't consider pre-emphasis at all.
      This kinda matches older DP specs that only had some vague text
      about transmitting the maximum voltage swing. Latest versions
      now say something vague about consider the sum of the vswing
      and pre-emphasis fields in the ADJUST_REQUEST_LANE registers.
      Very vague, and super confusing especially the fact that it
      talks about transmitted voltgage swing in the same sentence
      as it say to look at the requested values.
      
      Also glanced at the link CTS spec, and that one seems to have
      tests that assume contradicting behaviour. Some say to consider
      just the vswing level we transmit, others say to check for
      sum of transmitted vswing+preemph being 3.
      
      So let's try to take some kind of sane middle ground here.
      I think what could make sense is only consider max vswing
      reached if MAX_SWING_REACHED==1 _and_ vswing+preemph==3.
      That will allow things to go all the way up to vswing 3 +
      pre-emph 0 or vswing 2 + pre-emph 1, depending on what
      the maximum supported vswing is. Only considering the sum
      of vswing+pre-emph doesn't make much sense to me since
      we could terminate too early if the sink requests eg.
      vswing 0 + pre-emph 3. And if we'd stick to the current
      code we could terminate too early of the sink asks for
      vswing 2 + pre-emph 0 when vswing level 3 is not supported.
      
      Side note: I don't really understand why any of this stuff is
      "specified" at all. There is already a limit of 5 attempts at
      the same vswing+pre-emph level, and a total limit of 10
      attempts. So might as well stick to the same max 5 attempts
      across the board IMO.
      Signed-off-by: default avatarVille Syrjälä <ville.syrjala@linux.intel.com>
      Link: https://patchwork.freedesktop.org/patch/msgid/20211004170535.4173-2-ville.syrjala@linux.intel.comReviewed-by: default avatarImre Deak <imre.deak@intel.com>
      8bc2f5c3
  2. 05 Oct, 2021 1 commit
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  5. 30 Sep, 2021 4 commits