PCIe Link Training failed

We are trying to connect a PCIe switch through a mini PCIe port but we seem to have problems in link training. Reading the registers of the switch tells us that once link was up and then it went down. Moreover it also tells that auto corrected error was received and link training was failed.
My question is how can we debug link training or what are the reasons of failure of link training?
Can we just avoid the link training and forcefully set the link up?