u-boot/drivers/clk/at91/Kconfig

config CLK_AT91
	bool "AT91 clock drivers"
	depends on CLK
	help
	  This option is used to enable the AT91 clock driver.
	  The driver supports the AT91 clock generator, including
	  the oscillators and PLLs, such as main clock, slow clock,
	  PLLA, UTMI PLL. Clocks can also be a source clock of other
	  clocks a tree structure, such as master clock, usb device
	  clock, matrix clock and generic clock.
	  Devices can use a common clock API to request a particular
	  clock, enable it and get its rate.

config AT91_UTMI
	bool "Support UTMI PLL Clock"
	depends on CLK_AT91
	help
	  This option is used to enable the AT91 UTMI PLL clock
	  driver. It is the clock provider of USB, and UPLLCK is the
	  output of 480 MHz UTMI PLL, The souce clock of the UTMI
	  PLL is the main clock, so the main clock must select the
	  fast crystal oscillator to meet the frequency accuracy
	  required by USB.

config AT91_H32MX
	bool "Support H32MX 32-bit Matrix Clock"
	depends on CLK_AT91
	help
	  This option is used to enable the AT91 H32MX matrixes
	  clock driver. There are H64MX and H32MX matrixes clocks,
	  H64MX 64-bit matrix clocks are MCK. The H32MX 32-bit
	  matrix clock is to be configured as MCK if MCK does not
	  exceed 83 MHz, else it is to be configured as MCK/2.

config AT91_GENERIC_CLK
	bool "Support Generic Clock"
	depends on CLK_AT91
	help
	  This option is used to enable the AT91 generic clock
	  driver. Some peripherals may need a second clock source
	  that may be different from the system clock. This second
	  clock is the generic clock (GCLK) and is managed by
	  the PMC via PMC_PCR register.