Hi! Maybe it is wrong place to ask but I'll still try .
I wrote a (DMA) linux driver for Xilinx deviced (AXI-PCI core) and tested it with zc706 and vc707 devices. It works fine, but it looks like that the speed is limited to PCIe Gen1 4lane and I have absolutely no idea why. It never goes above 800 MB/s. I can only slow down it in half by changing the switch position on the board.
Lane of course might be broken, but I don't undersand what is wrong with Gen1/Gen2 thing. I tried it on motherboards with PCIe Gen2 support and on boards with Gen1 only. No difference. I think that I miss something on the kernel side or on the fpga side. It looks like that I need to switch it somewhere somehow. In AXI-PCI core settings there is only one tab which seems related: the one, where you change number of lanes and the link speed. Changing these setting actually change absolutely nothing for me. It is always around 800MB/s or slower.