u-boot/drivers/clk/Kconfig

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.
dm: Add a clock uclass Clocks are an important feature of platforms and have become increasing complex with time. Most modern SoCs have multiple PLLs and dozens of clock dividers which distribute clocks to on-chip peripherals. Some SoC implementations have a clock API which is private to that SoC family, e.g. Tegra and Exynos. This is useful but it would be better to have a common API that can be understood and used throughout U-Boot. Add a simple clock API as a starting point. It supports querying and setting the rate of a clock. Each clock is a device. To reduce memory and processing overhead the concept of peripheral clocks is provided. These do not need to be explicit devices - it is possible to write a driver that can adjust the I2C clock (for example) without an explicit I2C clock device. This can dramatically reduce the number of devices (and associated overhead) in a complex SoC. Clocks are referenced by a number, and it is expected that SoCs will define that numbering themselves via an enum. Signed-off-by: Simon Glass <sjg@chromium.org> 10 years ago			`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.`