How long does it take to erase iphone?

I have an iphone 4s and it is jail broken. Today the ios 7 came out so I was trying to un jail break it. I started by resetting it but that didn't undo the jail break. Then I pressed erased all data and restore and now the screen is black with the little swirling loading circle thing. It has been like this for over an hour now… Did I break my phone? Or is there something I can do to stop the erase? Or does it just take longer- if so how long?

U probably have to wait