[SOLVED] What's the difference between 'timebase-frequency' and 'clock-frequency' for Linux

Issue

I'm working with arm based linux, and start moving to risc-v, and I often see CPU nodes like the following one, in the dts:

    cpus {
            #address-cells = <0x1>;
            #size-cells = <0x0>;
            timebase-frequency = <0x989680>;

            cpu@0 {
                    device_type = "cpu";
                    reg = <0x0>;
                    status = "okay";
                    compatible = "riscv";
                    riscv,isa = "rv64imafdcsu";
                    mmu-type = "riscv,sv48";
                    clock-frequency = <0x3b9aca00>;

                    interrupt-controller {
                            #interrupt-cells = <0x1>;
                            interrupt-controller;
                            compatible = "riscv,cpu-intc";
                            linux,phandle = <0x1>;
                            phandle = <0x1>;
                    };
            };
    };

I wonder what timebase-frequency and clock-frequency refer to and what's the different between both ?

Solution

I initially thought you were asking about what the configuration entries mean; for those that do, they are described in Documentation/devicetree/booting-without-of.txt.

Since you are asking about the concept, however;

a timebase register is a register that is incremented at an implementation-dependent frequency - not necessarily once every clock cycle. Its purpose is to be used as a clock source (contrary to e.g. jiffies).

Answered By - Michael Foukarakis

Answer Checked By - Gilberto Lyons (WPSolving Admin)