- count_ticks: fix counter overflow handling,
- count_ticks: use reg_cycles variable in while loop,
- increment test: reduce number of cycles for slow cores if measure process needs to be repeated (difference is greater than 1).
On slow targets with fast high frequency tickers like NRF51_DK (16 Mhz CPU/1MHz ticker) time window for test case execution without overflow needs to be increased. Add parameter to `overflow_protect` function to be able to set different time window without overflow for us ticker and lp ticker.
Increment test proves that ticker counter is incremented by one.
This is done indirectly for high frequency counters where it is impossible to read 'value' and 'value + 1' in two successive ticker reads.
This check is done indirectly by counting ticker ticks elapsed during execution of N cycles of empty while loop. Unfortunately on slow boards with fast tickers like NRF51_DK(16 MHz CPU/1MHz hf ticker) it is possible that for the same N cycles measured number of elapsed ticks in two successive calls is greater than 1. This patch provides fix for such case - measure operation is repeated with the same number of cycles.
Since target specific ticker drivers are not ready also features which uses ticker in upper layers may not work correctly and tests for these features.
We need to disable also failing higher level ticker related tests (by adding check if DEVICE_USTICKER symbol is available and raise #error [NOT_SUPPORTED] if not).
Note:
tests-mbed_drivers-rtc is new and uses us ticker to perform a delay.
count_ticks() function counts ticker ticks elapsed during execution of N cycles of empty while loop.
In current version N value (cycles) is given as volatile paramater in order to disable possible compiler optimalisation.
There was a problem with measured time on different compilers and additionally results on ARM compiler were unexpected (the difference beetween measured elapsed ticks for the same number of cycles was to large). This might be caused by the memory access in order to store updated variable in memory. To fix this issue given numer of cycles has been stored into register and register is decremented (no memory access).
With this fix count_ticks(NUM_OF_CYCLES, 1) call returns 2500 +/-1 for us ticker ticks using each compiler (K64F).
On some platforms (e.g. K64F) different counters are used for time measurement and interrupt generation.
Because of that we should relax interrupt test case and give additional time before checking if interrupt handler has been executed.
Since according to the ticker requirements min acceptable counter size is 12 bits (low power timer) for which max count is 4095, then all test cases must be executed in this time window.
HAL ticker layer handles overflow and it is not handled in the target ticker drivers.
The intention was to use ticker_overflow_delta equal to 0 for low power ticker tests and ticker_overflow_delta equal to 50 for high frequency ticker tests. Current implementation is invalid since for devices which provide LOW_POWER_TIMER feature delta is equal to 0 and for devices without this feature delta is equal 50.
Since target specific ticker drivers are not ready also features which uses ticker in upper layers may not work correctly and tests for these features.
We need to disable also failing higher level ticker related tests (by adding check if DEVICE_USTICKER symbol is available and raise #error [NOT_SUPPORTED] if not).
These boards will be re-enabled when sleep driver for them is ready.
Note:
This operation is done by removing "SLEEP" feature from target's "device_has" list (in targets.json config file).
For NRF52_DK removing of "SLEEP" feature causes some timing issues which have influence on tests. In order to successfully disable this board we need to disable also related features like "USTICKER", "LOWPOERTIMER" and slightly modify ticker tests, so they will not be executed if usticker support is not available (by default all targets support us ticker).
With small wait time at the start, chances are that device does not
enter sleep and idle time is zero. Increasing wait time to make sure
device goes to sleep.
jeromecoutant
Przemyslaw Stekiel
Bartek Szatkowski
Russ Butler
Cruz Monrreal
Kevin Bracey
deepikabhavnani
Senthil Ramakrishnan
Asif Rizwan
Mika Leppänen
Michael Zhang
Amanda Butler