This bug in EDID was exposed by:

commit eccea7920cfb009c2fa40e9ecdce8c36f61cab66 Author: Alex Deucher alexander.deucher@amd.com Date: Mon Mar 26 15:12:54 2012 -0400

drm/radeon/kms: improve bpc handling (v2)

Which resulted in kind of regression in 3.5. This fixes https://bugs.freedesktop.org/show_bug.cgi?id=70934

Signed-off-by: Rafał Miłecki zajec5@gmail.com Cc: stable@vger.kernel.org --- 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 f1764ec..a1b4f2b 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 8bpc */ +#define EDID_QUIRK_FORCE_8BPC (1 << 8)

struct detailed_mode_closure { struct drm_connector *connector; @@ -128,6 +130,9 @@ static struct edid_quirk {

/* Medion MD 30217 PG */ { "MED", 0x7b8, EDID_QUIRK_PREFER_LARGE_75 }, + + /* Panel in Samsung NP700G7A-S01PL notebook reports 6bpc */ + { "SEC", 0xd033, EDID_QUIRK_FORCE_8BPC }, };

/* @@ -3421,6 +3426,9 @@ 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_8BPC) + connector->display_info.bpc = 8; + return num_modes; } EXPORT_SYMBOL(drm_add_edid_modes);