cpu/cc2538: timer broken? #6419
Description
On remote boards it appears that xtimer_usleep hangs. Didn't test on other cc2538 boards. Even tests/periph_timer acts weird as it can't initialise all timers:
2017-01-19 10:19:11,538 - INFO # Available timers: 4
2017-01-19 10:19:11,538 - INFO #
2017-01-19 10:19:11,539 - INFO # Testing TIMER_0:
2017-01-19 10:19:11,540 - INFO # TIMER_0: initialization successful
2017-01-19 10:19:11,540 - INFO # TIMER_0: stopped
2017-01-19 10:19:11,541 - INFO # TIMER_0: set channel 0 to 5000
2017-01-19 10:19:11,542 - INFO # TIMER_0: set channel 1 to 10000
2017-01-19 10:19:11,542 - INFO # TIMER_0: starting
2017-01-19 10:19:11,621 - INFO # TIMER_0: channel 0 fired at SW count 12309 - init: 12309
2017-01-19 10:19:11,623 - INFO # TIMER_0: channel 1 fired at SW count 76926 - diff: 64617
2017-01-19 10:19:11,624 - INFO #
2017-01-19 10:19:11,624 - INFO # Testing TIMER_1:
2017-01-19 10:19:11,625 - INFO # TIMER_1: ERROR on initialization - skipping
2017-01-19 10:19:11,626 - INFO #
2017-01-19 10:19:11,626 - INFO #
2017-01-19 10:19:11,627 - INFO # Testing TIMER_2:
2017-01-19 10:19:11,628 - INFO # TIMER_2: ERROR on initialization - skipping
2017-01-19 10:19:11,628 - INFO #
2017-01-19 10:19:11,628 - INFO #
2017-01-19 10:19:11,629 - INFO # Testing TIMER_3:
2017-01-19 10:19:11,629 - INFO # TIMER_3: ERROR on initialization - skipping
2017-01-19 10:19:11,630 - INFO #
2017-01-19 10:19:11,630 - INFO #
2017-01-19 10:19:11,630 - INFO # TEST FAILED