• Mario Kleiner's avatar
    drm/edid: Add 6 bpc quirk for display AEO model 0. · e10aec65
    Mario Kleiner authored
    Bugzilla https://bugzilla.kernel.org/show_bug.cgi?id=105331
    reports that the "AEO model 0" display is driven with 8 bpc
    without dithering by default, which looks bad because that
    panel is apparently a 6 bpc DP panel with faulty EDID.
    
    A fix for this was made by commit 013dd9e0
    ("drm/i915/dp: fall back to 18 bpp when sink capability is unknown").
    
    That commit triggers new regressions in precision for DP->DVI and
    DP->VGA displays. A patch is out to revert that commit, but it will
    revert video output for the AEO model 0 panel to 8 bpc without
    dithering.
    
    The EDID 1.3 of that panel, as decoded from the xrandr output
    attached to that bugzilla bug report, is somewhat faulty, and beyond
    other problems also sets the "DFP 1.x compliant TMDS" bit, which
    according to DFP spec means to drive the panel with 8 bpc and
    no dithering in absence of other colorimetry information.
    
    Try to make the original bug reporter happy despite the
    faulty EDID by adding a quirk to mark that panel as 6 bpc,
    so 6 bpc output with dithering creates a nice picture.
    
    Tested by injecting the edid from the fdo bug into a DP connector
    via drm_kms_helper.edid_firmware and verifying the 6 bpc + dithering
    is selected.
    
    This patch should be backported to stable.
    Signed-off-by: default avatarMario Kleiner <mario.kleiner.de@gmail.com>
    Cc: stable@vger.kernel.org
    Cc: Jani Nikula <jani.nikula@intel.com>
    Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
    Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
    Signed-off-by: default avatarDave Airlie <airlied@redhat.com>
    e10aec65
drm_edid.c 130 KB