In this technical note, the l(2) gain analysis and asynchronous H-infinity control problems for switched discrete-time linear systems are addressed. Under the dwell time constraint, the computation of l(2) gains versus dwell time is viewed as an open problem. By introducing a novel dwell time dependent Lyapunov function, an LMI-based sufficient condition is proposed to solve the l(2) gain analysis problem. Since the derived conditions are all convex in system matrices, it is convenient to be applied into H-infinity controller design. Thus, in the presence of asynchronous switching, an H-infinity controller is presented to ensure the closed-loop system with a desired non-weighted H-infinity performance. The proposed approach can also easily characterize the relationship between H-infinity performance, dwell time and asynchronous time. Finally, several academic examples are provided to illustrate our results. (C) 2014 Elsevier Inc. All rights reserved.