The share price of Rolls-Royce has now reached Credit Suisse's price target of 640p, and as such, the broker downgrades its rating on the aerospace and engine giant from 'outperform' to 'neutral'.Credit Suisse attributes other factors to the ratings change, such as less potential for upgrades as part of its sector growth analysis and recent reported Rolls-Royce engine incidents on the increase."With less catalysts ahead post the Tognum deal, we believe represents fair value," said analyst Nick Wilson. "Combined with a less attractive installed engine base than Safran [French defense and aerospace conglomerate], we downgrade."The price target is left at 640p.---BC