This adds documentation of device tree bindings for the clock related portions of the STM32 RCC block.
Signed-off-by: Daniel Thompson daniel.thompson@linaro.org --- .../devicetree/bindings/clock/st,stm32-rcc.txt | 65 ++++++++++++++++++++++ 1 file changed, 65 insertions(+) create mode 100644 Documentation/devicetree/bindings/clock/st,stm32-rcc.txt
diff --git a/Documentation/devicetree/bindings/clock/st,stm32-rcc.txt b/Documentation/devicetree/bindings/clock/st,stm32-rcc.txt new file mode 100644 index 0000000..fee3205 --- /dev/null +++ b/Documentation/devicetree/bindings/clock/st,stm32-rcc.txt @@ -0,0 +1,65 @@ +STMicroelectronics STM32 Reset and Clock Controller +=================================================== + +The RCC IP is both a reset and a clock controller. This documentation only +describes the clock part. + +Please also refer to clock-bindings.txt in this directory for common clock +controller binding usage. + +Required properties: +- compatible: Should be "st,stm32f42xx-rcc" +- reg: should be register base and length as documented in the + datasheet +- #clock-cells: 2, device nodes should specify the clock in their "clocks" + property, containing a phandle to the clock device node, an index selecting + between gated clocks and other clocks and an index specifying the clock to + use. + +Example: + + rcc: rcc@40023800 { + #clock-cells = <2> + compatible = "st,stm32f42xx-rcc", "st,stm32-rcc"; + reg = <0x40023800 0x400>; + }; + +Specifying gated clocks +======================= + +The primary index must be set to 0. + +The secondary index is the bit number within the RCC register bank, starting +from the first RCC clock enable register (RCC_AHB1ENR, address offset 0x30). + +It is calculated as: index = register_offset / 4 * 32 + bit_offset. +Where bit_offset is the bit offset within the register (LSB is 0, MSB is 31). + +Example: + + /* Gated clock, AHB1 bit 0 (GPIOA) */ + ... { + clocks = <&rcc 0 0> + }; + + /* Gated clock, AHB2 bit 4 (CRYP) */ + ... { + clocks = <&rcc 0 36> + }; + +Specifying other clocks +======================= + +The primary index must be set to 1. + +The secondary index is bound with the following magic numbers: + + 0 SYSTICK + 1 FCLK + +Example: + + /* Misc clock, FCLK */ + ... { + clocks = <&rcc 1 1> + };