What version of Uboot should I use?

Uboots are present for TI EVM & UD DVR boards. Uboot is not same for both DVR & EVM. You have to use based on the board you are using.

If we use our custom DM8168 board.

then I can choose anyone?And then modify/port to our board?

Yes.

But in our tests.

If board is selected to ti8168(evm),All cores and L3's frequency can be set as high as CCYG4 version allows.

However,if the board is selected to ti8168_dvr,only DSP and HDVICP's frequency can be set as high as CCYG4 version allows,if ARM,L3 or Ducati M3's frequency is set as high as CCYG4 version allows,the Uboot won't boot up.

Are there some limitions in ti8168_dvr board version?

Frequency limitations cannot be based on board version, it depends on the chip revision.

Issue you are seeing with dvr configuration selection for your custom board could be due to some other peripheral initialization. Please look into the code changes for UD_DVR configuration in uboot code.

I think so.

Maybe the limit is related to DVR config.

Thanks.I will try,