Can I have a road trip to Tibet without Chinese ID card but only chinese passport?

My husband and I are going to have a road trip from Chengdu to Lassa, Tibet in 2 weeks. We are citizens of P.R.China but do not have ID cards of china (shen fen zheng). Can we travel those area without ID card but only Chinese passport? Do we need any additional documents besides of our Chinese passports to go this trip? If yes, how to apply for those required documents?