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 panel. A fix for this was made by commit 013dd9e03872 ("drm/i915/dp: fall back to 18 bpp when sink capability is unknown"). However, that commit, while correct in itself, as a side effect triggers new regressions in precision for DisplayPort->DVI and DP->VGA displays. Patches are out to fix those regressions, but they 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. As the original patch was backported to stable and the fixes for regressions caused by that patch are aimed at stable, this patch should also go to stable to make everybody happy again. Signed-off-by: Mario Kleiner <mario.kleiner.de@xxxxxxxxx> Cc: Jani Nikula <jani.nikula@xxxxxxxxx> Cc: Ville Syrjälä <ville.syrjala@xxxxxxxxxxxxxxx> Cc: Daniel Vetter <daniel.vetter@xxxxxxxx> Cc: stable@xxxxxxxxxxxxxxx --- drivers/gpu/drm/drm_edid.c | 8 ++++++++ 1 file changed, 8 insertions(+) diff --git a/drivers/gpu/drm/drm_edid.c b/drivers/gpu/drm/drm_edid.c index ff28815..7d10537 100644 --- a/drivers/gpu/drm/drm_edid.c +++ b/drivers/gpu/drm/drm_edid.c @@ -74,6 +74,8 @@ #define EDID_QUIRK_FORCE_8BPC (1 << 8) /* Force 12bpc */ #define EDID_QUIRK_FORCE_12BPC (1 << 9) +/* Force 6bpc */ +#define EDID_QUIRK_FORCE_6BPC (1 << 10) struct detailed_mode_closure { struct drm_connector *connector; @@ -100,6 +102,9 @@ static struct edid_quirk { /* Unknown Acer */ { "ACR", 2423, EDID_QUIRK_FIRST_DETAILED_PREFERRED }, + /* AEO model 0 reports 8 bpc, but is a 6 bpc panel */ + { "AEO", 0, EDID_QUIRK_FORCE_6BPC }, + /* Belinea 10 15 55 */ { "MAX", 1516, EDID_QUIRK_PREFER_LARGE_60 }, { "MAX", 0x77e, EDID_QUIRK_PREFER_LARGE_60 }, @@ -3950,6 +3955,9 @@ int drm_add_edid_modes(struct drm_connector *connector, struct edid *edid) drm_add_display_info(edid, &connector->display_info, connector); + if (quirks & EDID_QUIRK_FORCE_6BPC) + connector->display_info.bpc = 6; + if (quirks & EDID_QUIRK_FORCE_8BPC) connector->display_info.bpc = 8; -- 2.7.0 _______________________________________________ dri-devel mailing list dri-devel@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/dri-devel
