arm(64)/dts/connect4: Reduce SPI frequency of KSZ9897
requested to merge github/fork/linosanfilippo-kunbus/fix/REVPI-1403/invalid_values_from_phy into devel/connect4/dt
Created by: linosanfilippo-kunbus
It turned out that if the SPI frequency for accessing the KSZ9897 is too high (more than 33MHz) the data read from the PHY registers may be corrupted if at the same time the USB is accessed. This may be caused by interferences between the SPI and USB signals. However reducing the frequency to a value below or equal to 33MHz for the SPI communication with the switch eliminates this effect. To be on the save side choose a value of 25MHz.
Signed-off-by: Lino Sanfilippo l.sanfilippo@kunbus.com