drm: don't add inferred modes for monitors that don't support them

commit 196e077dc165a307efbd9e7569f81bbdbcf18f65 upstream.

If bit 0 of the features byte (0x18) is set to 0, then, according to
the EDID spec, "the display is non-continuous frequency (multi-mode)
and is only specified to accept the video timing formats that are
listed in Base EDID and certain Extension Blocks".

For more information, please see the EDID spec, check the notes of the
table that explains the "Feature Support" byte (18h) and also the
notes on the tables of the section that explains "Display Range Limits
& Additional Timing Description Definition (tag #FDh)".

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=45729
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Reviewed-by: Adam Jackson <ajax@redhat.com>
Signed-off-by: Paulo Zanoni <paulo.r.zanoni@intel.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/gpu/drm/drm_edid.c b/drivers/gpu/drm/drm_edid.c
index 5a3770fbd770d63f2338fee03712917f80891146..584d5fdd1f30ee6eeb62427fe1d9cf0d71ebfefe 100644 (file)
--- a/drivers/gpu/drm/drm_edid.c
+++ b/drivers/gpu/drm/drm_edid.c
@@ -2020,7 +2020,8 @@ int drm_add_edid_modes(struct drm_connector *connector, struct edid *edid)
        num_modes += add_cvt_modes(connector, edid);
        num_modes += add_standard_modes(connector, edid);
        num_modes += add_established_modes(connector, edid);
-       num_modes += add_inferred_modes(connector, edid);
+       if (edid->features & DRM_EDID_FEATURE_DEFAULT_GTF)
+               num_modes += add_inferred_modes(connector, edid);
        num_modes += add_cea_modes(connector, edid);
 
        if (quirks & (EDID_QUIRK_PREFER_LARGE_60 | EDID_QUIRK_PREFER_LARGE_75))