The .dts files in the kernel source set the I2C bus speeds. Looking at android source file rk3399-nanopi4-common.dtsi we have:
&i2c0 {
status = "okay";
i2c-scl-rising-time-ns = <160>;
i2c-scl-falling-time-ns = <30>;
clock-frequency = <400000>;
&i2c1 {
status = "okay";
i2c-scl-rising-time-ns = <150>;
i2c-scl-falling-time-ns = <30>;
clock-frequency = <200000>;
&i2c2 {
status = "okay";
};
&i2c4 {
status = "okay";
i2c-scl-rising-time-ns = <160>;
i2c-scl-falling-time-ns = <30>;
clock-frequency = <400000>;
I think the ones that don't specify clock speed default to 100KHz.
Mike