I have enabled the AD9361 in Fast Attack AGC mode per the example from the "AD9361 Gain Control and RSSI User Guide" v2.8
I am using a signal generator to input short signals. Specifically this is an LTE uplink Random Access Preamble, approxmiately 1ms long. The AGC works well at reducing the gain to accomodate high strength signals, but never seems to unlock. The gain never goes back up, and low strength signals are no longer detected.
Edit: I've used the output from control register 0x35 to verify that the AGC remains in state 5 after the signal is turned off. Here is the AD9361 register configuration I used.