riscv,machine-timer

Vendor: RISC-V Foundation

Description

RISC-V Machine timer

Properties

Properties not inherited from the base binding file.

Name

Type

Details

clk-divider

int

 
clk-divider specifies the division ratio to the CPU frequency that
clock used by machine timer.
This property supports the case that the machine timer and CPU use
different clock sources.
This configuration is used sometimes for such as low power consumption.

For example, the CPU clock frequency is 108MHz, and the machine timer
uses 27MHz, which is the CPU clock divided by 4.
In this case, the CPU clock frequency is defined in the CPU node
as follows

   clock-frequency = <108000000>;

This property takes exponent of the power of 2.
The relationship with the frequency division ratio is as
following equation.

   division_ratio = 2^n
   n = log_2(division_ratio)

Setting clk-divider to 2 specifies the machine timer uses the clock
that CPU clock frequency divided by (2^2=)4, or 27MHz.

Devision ratio constants can be found in the
dt-bindings/timer/nuclei-machine-timer.h header file.