The number of delay taps in the LA data path can be controlled manually, from
the regmap or automatically, according to the axi_adc_decimate's rate.
Moreover, because the rate is configure by software, and the time of
initialization, is different for the ADC path and LA path. There is an
uncertainty of plus/minus one sample between the two. Because ADC and LA
paths share the same clock we can easily synchronize the two paths. We
can't use reset, because the rate generation mechanism is different
between the two. So the ADC path is used as master valid generator and we
can use it to drive the LA path.
The synchronization is done by setting the rate source bit. This
mechanism can only be used if the desired rate for both path is equal,
including oversampling fom ADC decimation.
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