Thank you all the same,Biser.
I think I have some problems in software,I made some changes linux kernel to configure the interface of rmii2.
I started the board,then I connected the board to the network,the serial port printed that:
net eth0: CPSW phy found : id is : 0x7c0f1
PHY: 0:00 - Link is Up - 100/Full.
I executed udhcpc, it printed that
Sending discover...
Sending discover...
No lease, failing
Then I measured the RMII2 TX pins of am3359,I found there was not data trasmission.