Commit 797e45d6bfc467743a3ff350858d2169cad5126e attempted to reduce the frequency of SPI reconfiguration by keeping track of the current frequency and mode settings and changing these settings only when the new settings differ from the old settings.
However, the original commit neglected to save the new frequency setting and, hence, was not effective in what it was trying to do: Every time the SPI setfrequency() method was called, it still looked like a new frequency and the frequency was still reconfigured, even though it hadn't really changed.
78563d555a