Unable to write on root port when two Xavier boards use PCIe to communicate, always get 0xFFFFFFFF

[ruiyingw]

Hi,

I am having an issue to write at the first address(shown by “lspci -v”) on the root port.

1. My system:
   

   

2. I did the instructions as mentioned on this site

→ Flashing PCIe endpoint [Done]
→ Connecting and configuring the system [Done]
→ Test bidirectional communication [Failed]

Details about failure:

1. I can read/write on endpoint device using busybox
2. when I try to write on the root port device, it is always 0xFFFFFFFF. Details are shown below

The address I used is based on “lspci -v” on root port, which is 0x1f40400000

Then I tried the following on root port:

As shown above, no matter what I wrote, it is always 0xFFFFFFFF

Then I tried “dmesg|grep pci” to check any related errors. But didnt find any related error messages. The two dmesg output files for root port and endpoint have been attached.endpoint.txt (6.7 KB) root_port.txt (8.4 KB)

And the TX-RX switch board also can cause the issue.

So not sure how to narrow down where the issue might be and debug.

Any suggestions would be appreciated!

[vidyas]

It is not clear if the device driver for the endpoint (i.e. AGX-EP) is being binded with the device on the root port. Could you please attach the ‘sudo lspci -vvvv’ output on the host machine? If you don’t see something like “Kernel driver in use: tegra_ep_mem” for the endpoint device in host machine, then, there is something wrong with your setup.
without the device driver, the memory/IO window and also BME (Bus Master Enable) bits in the configuration space of the EP device (i.e. AGX-EP) wouldn’t have been enabled by anyone hence you observe 0xF response for any read to the BAR.