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

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)".

Cc: stable@vger.kernel.org
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>

diff --git a/drivers/gpu/drm/drm_edid.c b/drivers/gpu/drm/drm_edid.c
index e1aca7b5398775dd97830dec47a68684731917d9..67aa0dd68250a8ca330bc8f3005a9e924d79ff8d 100644 (file)
--- a/drivers/gpu/drm/drm_edid.c
+++ b/drivers/gpu/drm/drm_edid.c
@@ -2054,7 +2054,8 @@ 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))