For STM32 targets using a 32-bit timer for the microsecond ticker, the
driver did not properly handle timestamps that are in the past. It
would just blindly set the compare register to the requested timestamp,
resulting in the interrupt being serviced up to 4295 seconds late
(i.e. after the 32-bit timer counts all the way around to hit the
timestamp again).
This problem can easily be reproduced by creating a Timeout object
then calling the timeout's attach_us() member function to attach a
callback with a timeout of 0 us. The callback will not get called for
over 2147 seconds, and possibly up to 4295 seconds late if no other
microsecond ticker events are getting scheduled in the meantime.
Now, after the compare register has been set, the timestamp is checked
against the current time to see if the timestamp is in the past, and
if so, the compare event is manually set.
NOTE: By checking if the timestamp is in the past after configuring the
capture register, we ensure proper handling in the case where the timer
updates past the timestamp while setting the capture register.
Only one point of attention:
STM_MODE_ANALOG_ADC_CONTROL is a specific mode that is only supported on L4.
So STM_MODE_ANALOG_ADC_CONTROL was moved to index 13 (last entry)
of gpio_mode table so that all the other modes are common and only the last
one is specific.
Sam Grove
Bradley Scott
Bartek Szatkowski
jeromecoutant
Martin Kojtal
Laurent MEUNIER
bcostm
Christopher Haster