drm/edid: Reset more of the display info

We're currently failing to reset everything in display_info.hdmi
which will potentially cause us to use stale information when
swapping monitors. Eg. if the user replaces a HDMI 2.0 monitor
with a HDMI 1.x monitor we will continue to think that the monitor
supports scrambling. That will lead to a black screen since the
HDMI 1.x monitor won't understand the scrambled signal.

Fix the problem by clearing display_info.hdmi fully. And while at
eliminate some duplicated code by calling drm_reset_display_info()
in drm_add_display_info().

Cc: stable@vger.kernel.org
Cc: Antony Chen <antonychen@qnap.com>
Cc: Shashank Sharma <shashank.sharma@intel.com>
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=105655
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20180424130250.7028-1-ville.syrjala@linux.intel.com
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Tested-by: Antony Chen <antonychen@qnap.com>
Signed-off-by: Sean Paul <seanpaul@chromium.org>

drivers/gpu/drm/drm_edid.c

@@ -4451,6 +4451,7 @@ drm_reset_display_info(struct drm_connector *connector)
 	info->max_tmds_clock = 0;
 	info->dvi_dual = false;
 	info->has_hdmi_infoframe = false;
+	memset(&info->hdmi, 0, sizeof(info->hdmi));
 
 	info->non_desktop = 0;
 }
@@ -4462,17 +4463,11 @@ u32 drm_add_display_info(struct drm_connector *connector, const struct edid *edi
 
 	u32 quirks = edid_get_quirks(edid);
 
+	drm_reset_display_info(connector);
+
 	info->width_mm = edid->width_cm * 10;
 	info->height_mm = edid->height_cm * 10;
 
-	/* driver figures it out in this case */
-	info->bpc = 0;
-	info->color_formats = 0;
-	info->cea_rev = 0;
-	info->max_tmds_clock = 0;
-	info->dvi_dual = false;
-	info->has_hdmi_infoframe = false;
-
 	info->non_desktop = !!(quirks & EDID_QUIRK_NON_DESKTOP);
 
 	DRM_DEBUG_KMS("non_desktop set to %d\n", info->non_desktop);