config CLK bool "Enable clock driver support" depends on DM help This allows drivers to be provided for clock generators, including oscillators and PLLs. Devices can use a common clock API to request a particular clock rate and check on available clocks. Clocks can feed into other clocks in a tree structure, with multiplexers to choose the source for each clock.config SPL_CLK_SUPPORT bool "Enable clock support in SPL" depends on CLK help The clock subsystem adds a small amount of overhead to the image. If this is acceptable and you have a need to use clock drivers in SPL, enable this option. It might provide a cleaner interface to setting up clocks within SPL, and allows the same drivers to be used as U-Boot proper.