Driver for PCI: pci_resource_start returns 0x0

Hello,

I'm developing a kernel driver for an FPGA.
The driver runs under Xilinx linux kernel.
Calling to pci_resource_start (pDev,0) return 0x0.

The BAR size requested by hardware is 512MB.

I ran the same driver with another PCI card that needs much smaller BAR.
In this case pci_resource_start returned a valid address.

Can I configure \ fix something in the kernel so that pci_resource_start will work also with 512MB BAR size ?

Thank you,
Zvika