quoted

I already explain how this works once. Please read this thread again.... The
MAC can apply the delays, but it must mask the phy-mode it passes to the PHY.

Yes. I have read these mails.

I understand what you mean.
"rgmii": delay on PCB, not MAC or PHY.
"rgmii-id": delay on MAC or PHY, not PCB.

ftgmac100 driver gets phy driver handle from of_phy_get_and_connect(), it will pass the phy-mode to
phy driver from the node of mac dts.
Therefore, I use "rgmii-id" and the phy will enable tx/rx internal delay.
If I use "rgmii-id" and configure the RGMII delay in ftgmac100 driver, I cannot pass the phy-mode to 
phy driver.

Quoting myself, yet again:

quoted

MAC can apply the delays, but it must mask the phy-mode it passes to the PHY.

If you decide the MAC does the RX clock delay, it needs to mask that
from the phy-mode, otherwise the PHY will also do it. If you decide
the MAC does the TX clock delay, its needs to mask that from the
phy-mode.

	Andrew