Which one is more grammatically correct?
He was woken up by his alarm clock.
He was woken by his alarm clock.
In OP’s context, up makes no difference to the meaning, and isn’t included in most usages…
…but as the chart implies, there’s nothing particularly “unusual” about including it, either.
But in contexts where the “base” verb to wake actually ends a clause, we’re much more likely to include the preposition. It’s not easy for me to show this by charts or corpus searches, but if you look at…
…it seems clear to me up is present more often than not when there’s no additional text in the utterance.
There’s no actual “rule” in play here – but idiomatically, native speakers have a tendency to discard up when there’s another preposition following the full phrasal verb form to wake up.
Source : Link , Question Author : alexchenco , Answer Author : FumbleFingers