When using the UART to continuously transmit data while changing often the CTS input, the UART locks up and stops transmitting. I was able to easily reproduce the problem with the WS2812B LED interface chip here:
https://www.kickstarter.com/projects/1338646202/simple-ws2812b-led-interface-controller-chip
when using it in Example 5. I managed to reproduce the problem with kernels 3.6.11 and 4.1.16.
I investigated the issue and found out that the kernel requires cts_event_workaround variable in the vendor_arm structure in amba-pl011.c to be initialized to true.
This issue has been reported and addressed for Linaro platforms in the past:
https://patches.linaro.org/1837/
https://patches.linaro.org/7461/
I built the 4.1.16 kernel with this fix and couldn’t reproduce the problem.