drm/i915: Fix for LVDS VBT change on IGDNG

IGDNG mobile chip's LVDS data block removes panel fitting
register definition. So this fixes offset for LVDS timing
block parsing. Thanks for Michael Fu to catch this.
Signed-off-by: NZhenyu Wang <zhenyu.z.wang@intel.com>
Signed-off-by: NEric Anholt <eric@anholt.net>

drivers/gpu/drm/i915/intel_bios.c

@@ -97,6 +97,7 @@ static void
 parse_lfp_panel_data(struct drm_i915_private *dev_priv,
 			    struct bdb_header *bdb)
 {
+	struct drm_device *dev = dev_priv->dev;
 	struct bdb_lvds_options *lvds_options;
 	struct bdb_lvds_lfp_data *lvds_lfp_data;
 	struct bdb_lvds_lfp_data_ptrs *lvds_lfp_data_ptrs;
@@ -132,7 +133,14 @@ parse_lfp_panel_data(struct drm_i915_private *dev_priv,
 	entry = (struct bdb_lvds_lfp_data_entry *)
 		((uint8_t *)lvds_lfp_data->data + (lfp_data_size *
 						   lvds_options->panel_type));
-	dvo_timing = &entry->dvo_timing;
+
+	/* On IGDNG mobile, LVDS data block removes panel fitting registers.
+	   So dec 2 dword from dvo_timing offset */
+	if (IS_IGDNG(dev))
+		dvo_timing = (struct lvds_dvo_timing *)
+					((u8 *)&entry->dvo_timing - 8);
+	else
+		dvo_timing = &entry->dvo_timing;
 
 	panel_fixed_mode = kzalloc(sizeof(*panel_fixed_mode), GFP_KERNEL);