From b17226ca4e6cb50d3bbb0215fd8208ffdf44bf63 Mon Sep 17 00:00:00 2001 From: Mario Kleiner Date: Wed, 6 Jul 2016 12:05:44 +0200 Subject: [PATCH] drm/edid: Add 6 bpc quirk for display AEO model 0. MIME-Version: 1.0 Content-Type: text/plain; charset=utf8 Content-Transfer-Encoding: 8bit commit e10aec652f31ec61d6a0b4d00d8ef8d2b66fa0fd upstream. 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 013dd9e03872 ("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: Mario Kleiner Cc: Jani Nikula Cc: Ville Syrjälä Cc: Daniel Vetter Signed-off-by: Dave Airlie [bwh: Backported to 3.2: adjust context] Signed-off-by: Ben Hutchings --- 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 72f460e22b76..bcfcfbb32877 100644 --- a/drivers/gpu/drm/drm_edid.c +++ b/drivers/gpu/drm/drm_edid.c @@ -68,6 +68,8 @@ #define EDID_QUIRK_DETAILED_SYNC_PP (1 << 6) /* Force reduced-blanking timings for detailed modes */ #define EDID_QUIRK_FORCE_REDUCED_BLANKING (1 << 7) +/* Force 6bpc */ +#define EDID_QUIRK_FORCE_6BPC (1 << 10) struct detailed_mode_closure { struct drm_connector *connector; @@ -94,6 +96,9 @@ 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 }, @@ -1752,6 +1757,9 @@ int drm_add_edid_modes(struct drm_connector *connector, struct edid *edid) drm_add_display_info(edid, &connector->display_info); + if (quirks & EDID_QUIRK_FORCE_6BPC) + connector->display_info.bpc = 6; + return num_modes; } EXPORT_SYMBOL(drm_add_edid_modes); -- 2.39.2