EXACT SAME PROBLEM! It took me ages to find the problem! Mine is a E7240 and my CPU frequency is stuck at 20% after resume from sleep. I bought the PC for about 1400 Euros! and I'm not happy to have to close all my running applications every time for a full restart to fix the issue! My Bios is the latest version? Is this a hardware issue?
@sabahang: I do not think the root issue here is a hardware problem, but rather an incompatibility between the use of Clock Modulation and the intel_pstate CPU frequency scaling governor.
You might be right! I couldn't find a way to change frequency using native OS tools after a resume however I managed to tweak pstate using a software called ThrottleStop. I also upgraded my Bios to latest revision (rev16 I believe). Now when I resume the max freq is not so low anymore. it is around 60-70% percent whereas previously it was painfully around 25% and I couldn't change it. Whenever I hit the frequency limit and I can't seem to change it using High Performance power plan I use ThrottleStop to change it. Very useful app