PCIe bringup in Agilex 5

Hi,

I am working on PCIe bring-up on an Intel Agilex 5 SoC FPGA platform using the Altera PCIe Root Port IP in Root Port mode.

Current status:

PCIe root port is detected properly

NVMe endpoint is also enumerated correctly

lspci shows both root port and NVMe device successfully

However, I am facing two major issues:

During NVMe probe, I sometimes get:

nvme nvme0: I/O tag 0 (1000) QID 0 timeout, completion polled

If probe succeeds and I try actual read/write operations on the NVMe drive, the system crashes/hangs with RCU stall or timeout related logs.

I have already checked:

PCIe link comes up correctly

BARs are assigned

Bus master enabled

Endpoint enumeration looks fine

I also tried:

pci=nomsi

but then NVMe probe fails with error -22.

This makes me suspect the issue may be related to:

MSI/MSI-X interrupt handling

DMA configuration

outbound address translation

or cache coherency issues

Has anyone seen similar behavior on Agilex 5 or Altera PCIe Root Port IP where:

enumeration works

but NVMe probe times out or crashes during I/O?

Any suggestions on what to debug next would be very helpful.

Thanks.