Tx2 I2C4 (I2C_PM) no working

On Tx2 board, we try to use i2c4 to read/write device register,

  1. execute command: i2cdetect -y -r 4;
  2. use Oscilloscope to detect pin5 in J27 header;

but no any wave happened on Oscilloscope…
Does i2c4 disable default?
How should I enable and use it?

This pin is gen_i2c_xx aka i2c8 aka software i2c bus 7