TimMasterHandle.Instance initialization can be removed from here,
because it will either have been already done previously,
or it will be done in the us_ticker_init() call immediately below.
Following previous fixes on 16 tickers handling, the overflow flag
condition will not happen anymore, so the work-around in place is
not needed anymore
This commit simplifies ticker interrupt set function and handler.
There were issues around the 16 bits timer wrap-around timing as we were
aligning interrupts with wrap-around limits (0xFFFF) and then reading
TIM_MST->CNT again in timer_update_irq_handler which could lead
to crossing case with the wrap-around (TIM_FLAG_UPDATE) case.
Now we're using the 16 lower bits of the timestamp as the reference from
using in set_compare and never changing it. There is also no need to set
comparator again in timer_update_irq_handler. This is more robust and
also more efficient.
Move to a single more reliable implementation of us_ticker_read()
There were historically 2 versions of us_ticker_read() implementation.
The one removed here was not reliable because us_ticker_read() can be
called in interrupt context which means that TIM_MST->CNT would have
wrapped around while SlaveCounter is not yet updated. So there is a need
to check the TIM_FLAG_UPDATE inside this function, which was not done in
the implementation that is removed here.
Laurent MEUNIER
bcostm