gma500: Prevent endless loop in panel power up sequence

Some devices don't have a panel connected to LVDS and thus will never power up.
This patch checks the power sequence progress bits in PP_STATUS to prevent an
endless loop on such devices.

Signed-off-by: Patrik Jakobsson <patrik.r.jakobsson@gmail.com>
Signed-off-by: Alan Cox <alan@linux.intel.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>

drivers/gpu/drm/gma500/psb_lid.c

@@ -40,10 +40,16 @@ static void psb_lid_timer_func(unsigned long data)
 		REG_WRITE(PP_CONTROL, REG_READ(PP_CONTROL) | POWER_TARGET_ON);
 		do {
 			pp_status = REG_READ(PP_STATUS);
-		} while ((pp_status & PP_ON) == 0);
+		} while ((pp_status & PP_ON) == 0 &&
+			 (pp_status & PP_SEQUENCE_MASK) != 0);
 
-		/*FIXME: should be backlight level before*/
-		psb_intel_lvds_set_brightness(dev, 100);
+		if (REG_READ(PP_STATUS) & PP_ON) {
+			/*FIXME: should be backlight level before*/
+			psb_intel_lvds_set_brightness(dev, 100);
+		} else {
+			DRM_DEBUG("LVDS panel never powered up");
+			return;
+		}
 	} else {
 		psb_intel_lvds_set_brightness(dev, 0);