About problem with using EMAC splitter and GMII_TO_RGMII

Hello,
I am newer.

One of EMAC in HPS is being used by the construction with the pin of FPGA.
The design of the hardware is reference of the following site.
(https://rocketboards.org/foswiki/view/Projects/CycloneVRGMIIExampleDesign)

Now, Hardware guy is gone.

When I tried to do ping test by using WindowsPC, I confirmed it worked fine in 10Mbps(Full/Half), 1000Mbps.

But It failed only at 100Mbs.

So I have investigated now, and I did following procedure,

  • Set the ctrl register of System Manager(0xFFD08060) to “1” (RGMII).

It works fine. It passes ping test at 10Mbps, 100Mbps and 1000Mbps.

But I do not understand why?
I think that EMAC may be connected to GMII_TO_RGMII IP package.
So the value of ctrl register of System Manager(0xFFD08060) shall be “0”(GMII).
Please tell me why.

Best Regards,
H.Wada