If your backlight has an issue after waking up from sleep you probably need to add the following to your dsdt file:

+        Device (PNLF)
+        {
+                Name (_HID, EisaId ("APP0002"))
+                Name (_CID, "backlight")
+                Name (_UID, 0x0A)
+                Name (_STA, 0x0B)
+        }
         Device (PWRB)
             Name (_CID, EisaId ("PNP0C0C"))

the full dsdt source code can be found on my github or just get the compiled dsdt.aml