How to change I2C speed

[u26]

hello scopiochang  chobio,

I try to i2c speed up too.

> scopipchang
thank you for your dts file and infomation about how to import.

so, I will send my hw_intf.conf, dts and dtbo.
could you check it ?

and I found the file "clock-frequency" here in tinkerboad. 
> ls /sys/firmware/devicetree/base/i2c*

i2c@ff140000:
#address-cells  clock-frequency  clocks      interrupts  phandle    pinctrl-names  status
#size-cells     clock-names      compatible  name        pinctrl-0  reg


Does i2C1 become 400000bps ??

thanks