--- a/drivers/gpu/drm/radeon/cik.c	2014-05-26 15:00:23.668202048 +0800
+++ b/drivers/gpu/drm/radeon/cik.c	2014-05-26 15:03:01.280196776 +0800
@@ -7953,11 +7953,22 @@
 		struct radeon_connector *radeon_connector = to_radeon_connector(connector);
 		bpc = radeon_get_monitor_bpc(connector);
 		dither = radeon_connector->dither;
+		//dither found to be 0 in lvds laptop,don't know why dither is 0, 
+		//it's value is read from BIOS, BIOS supposed know that dither should be 1 if in use of laptop LVDS panel
+		//just set dither to 1 if bpc is not equal to depth
+		dither = ((bpc*3) != encoder->crtc->fb->depth )?RADEON_FMT_DITHER_ENABLE:dither;	
+		radeon_connector->dither = dither;
 	}
 
 	/* LVDS/eDP FMT is set up by atom */
-	if (radeon_encoder->devices & ATOM_DEVICE_LCD_SUPPORT)
-		return;
+	if (radeon_encoder->devices & ATOM_DEVICE_LCD_SUPPORT){
+		//radeon driver suppose BIOS already set the "fmt_bit_depth_control" register well (0xa100,dithering enabled,6bpc panel)
+		//but function "atombios_set_encoder_crtc_source()" call bios with command "selectCRTC_Source" and set this register to 0,
+		//which causes color banding bug(see bugzilla[73911])
+		//not sure whether command "selectCRTC_Source" hardcoded to clear the register or parameters radeon passed to bios
+		//indicts BIOS to clear the register.
+		//Anyway,just let driver set the register to a correct value is no harm.
+	}
 
 	/* not needed for analog */
 	if ((radeon_encoder->encoder_id == ENCODER_OBJECT_ID_INTERNAL_KLDSCP_DAC1) ||