TMS320F28388D: MDIO clock: CSR clock source?

Tool/software:

I am using the F28388D control card. I have a working ethernet implementation (with the TI BIOS + NDK) but would like to determine the MDIO clock being used.

Reading the reference manual, I ended up in the register "MAC_MDIO_Address" (page #4798), bitfield "CR".

The manual mentions a "CSR clock" but I got no information in the data sheet where this "CSR clock" comes from.
Is it derived from the CM clock, from the Ethernet clock, ....?

My clock configuration is:
* CPU 1 clock = 200 MHz
* AUX clock = 125 MHz
* CM uses AUX clock
* Ethernet clock = System clock with divider 2 = 100 MHz

Thank you,
Markus