Avalon-MM PCIe connecting two FPGAs not working

Hi,

I try to connect two Cyclone V SoCs by a highspeed transceiver using the Avalon-MM PCIe core.

One FPGA is configured as root the other as endpoint. The PCIe link between both FPGAs is up (ltssmstate keeps in L0).

If I try to do a read transaction on the Txs Interface of the root the Avalon bus stalls. As fare as I can see the bus master flag is not set an therefore the state machine is not generating the PCIe packets (no tx_st_* signals are changing).

How can I set the bus master flag?

Do I have a wrong understanding for using this cores?