[ipq40xx] What is ess-switch? Why I cannot ping to my pc when I disable ess-switch?

Hi every one, I have my own ipq40xx image. I use spi-nor flash. However, I have a problem, the ess-switch prevent my Uboot autoboot. It cause a kernel panic. (manual boot work well @@)
Then I disable the ess-switch, the kernel can autoboot, now. However, I cannot ping via ethernet port.
And it said that my ethernets are entered promiscuous mode.?

Thank you very much