Problem phenomenon：

Network often LINK UP 10/Half or 100/HALF or 100/Full

Very unstable.

When I actually found that I.MX6 is configured to RMII, the MDC clock is 8MHz

Then check the specification book of LAN8720

The maximum MDC can only be 2.5MHz.

So there are problems here, so check the specification book of I.MX6

Register MII Speed Control Register (ENET_MSCR)

Because we use the external 50MHz active clock to connect GPIO16, guess that the internal MAC clock will not be lower than 50MHz, so modify the MSCR to 0x9.

You can use it at this time