Re: PCIe interface memory memory mapping issue

[Sanka Piyaratna <cesanka@yahoo.com>]

Hi Robert


Thanks for your reply.

>> I have developed a PCI express interface using Xilinx ML555 hardware module. I have implemented Linux kernel >>mode device drivers and everything works correctly as long as I am using the device within a computer with dual >>channel DDR arrangement. However, as soon as I pug this device into a core i7 or an older single channel DDR >>machine, the interface memory mapping does not work any more. As if the register map with in the device does no >>longer exsists. However, "lspci" utility provides correct information. I am not sure if this has anything to do with the >>number of DDR memory channels the motherboard has or why that would be a problem for PCI express device. >>However, this seem to be the common link between the machines that demonstrate this issue.

>You'll have to give more details on what you mean by "the interface memory mapping does not work any more. As if >the register map with in the device does no longer exsists".

What I mean by this is that, when load the driver, the memory mapping of the hardware memory onto the computer memory does not work. I have a setup where I have all the control registers in BAR5 (512 byte) and I also have 64kB chuck of the FPGA memory mapped using BAR0. I am not able to see the register space when the BAR5 area in the computer memory map. However, I am able to write something to BAR0 memory map and read it back.

Thanks and regards,

Sanka



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