Debugging PCIe transfers on IVB iGPU

[SimonRichter]

Hi,

I'm trying to pull data from an FPGA card into the iGPU on an older IVB system. This machine has an 8086:0150 Host Controller as 0:00.0, and an 8086:0162 iGPU as 0:02.0; the FPGA is connected as 1:00.0.

I have created a p2p dma_buf in Linux, exported that from my driver as a file descriptor, imported it on Vulkan, and am now trying to vkCopyImage data from the imported image to a texture, converting to Y0 layout in the process. I get no complaints from the validation layer, and adding a bunch of printk()s allowed me to validate that the GPP PTEs for the BAR are created, but no TLPs arrive.

Checking the opposite direction with a read request to the 256M prefetchable range of the iGPU device

00000002
0100aaff
e0000048

gives me back UR

0a000000
00002008
0100aa48

while for arbitrary memory addresses, e.g.

00000002
0100aaff
50000048

I get successful completion with some garbage data

4a000002
00000008
0100aa48
xxxxxxxx
xxxxxxxx

The UR seems to be generated by the root complex, which would suggest that I can't use address-routed TLPs between devices, which would also explain why I'm not seeing a TLP from the iGPU in my FPGA. Is that correct, or have I forgotten something?

   Simon

[Alberto_R_Intel]

SimonRichter, Thank you for posting in the Intel® Communities Support.

In reference to this scenario, we will do further research on this matter in order to provide the most accurate response to your inquiry or to point you in the right direction for the proper support. As soon as I get any updates, I will post all the details on this thread.

Any questions, please let me know.

Regards,

Albert R.

Intel Customer Support Technician

[Alberto_R_Intel]

Hello SimonRichter, I just received an update on this matter.

I just transfer your case to the proper department. They will further assist you with this subject as soon as possible.

Regards,

Albert R.

Intel Customer Support Technician