When initializing the RTC on Kinetis devices, handle the case where
the time overflow interrupt is pending and the case where the time
alarm flag is pending. These flags persist across reset and if not
handled will cause a crash when powering up the low power ticker.
This problem manifested as a lp_ticker test failure on the K22F and
K64F on CI only when running a nightly. This problem has been present
but was made obvious by PR #4094 which configures all tickers to
interrupt at least every MBED_TICKER_INTERRUPT_TIMESTAMP_MAX_DELTA
(~31 minutes). This caused the RTC alarm to fire 31 minutes after the lp_ticker
or lp_timeout test and caused the next run of the lp_ticker test to
crash on boot.
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.
There is an easy default implementation of spi_master_block_write that
just calls spi_master_write in a loop, so the default implementation
of spi_master_block_write has been added to all targets.
Sam Grove
Russ Butler
Anna Bridge
Laurent MEUNIER
Yuguo Zou
ianqianting