TDA4VM: PCIe mode on M2 connector

Hi Shine,

For PCIe loopback, do you mean loopback as described in this documentation: https://software-dl.ti.com/jacinto7/esd/processor-sdk-linux-jacinto7/09_01_00_06/exports/docs/linux/Foundational_Components/Kernel/Kernel_Drivers/PCIe/PCIe_End_Point.html?highlight=loopback

If yes, we have not tested PCIe EP/RC examples with the M.2 connector. However, if a cable can be found to connect the M.2 connector, then applying a dts change similar to the changes described in "DTS Modification" section except for the PCIE2 interface should theoretically get the same behavior as PCIE0 and 1 interfaces.

Regards,

Takuma

Hi Takuma,

Thank you very much.

Customer only has one EVM board, he wants to realize the loopback mode only on one EVM board with M.2 connector.

Thanks
Regards
Shine

Hi Shine,

From what I can find, it seems we do not support loopback mode in our PCIe driver. The driver assumes RC or EP configuration for each port: https://git.ti.com/cgit/ti-linux-kernel/ti-linux-kernel/tree/drivers/pci/controller/cadence/pcie-cadence-plat.c?h=ti-linux-6.1.y#n68

As an alternative, what can be possible would be:

• External loopback using a cable between the PCIe ports on the top side of the EVM (aka, connect the PCIe ports J8 and J11 with the cable in SDK documentation, and configure one port as RC, and the other port as EP)
• Connecting a SSD card on the M.2 port and doing read/write to test basic read/write functionality

In parallel, checking with the team to see if we have another alternative, but I would like to set expectations that we most likely do not have a loopback example from one connector.

Regards,

Takuma

Hello Takuma, 

Thank you very much.

Takuma Fujiwara said:

External loopback using a cable between the PCIe ports on the top side of the EVM (aka, connect the PCIe ports J8 and J11 with the cable in SDK

In the TDA4VM schematic, the J8 is ethernet port, J11 is M.2 port, so can customer use J8 as pcie port?

Regards
Shine