J784S4XEVM: Ring Accelerator access from user mode (EL0) on TDA4VH

Zoltan Laszlo

Part Number: J784S4XEVM

Tool/software:

Is it possible to access the push/pop addresses of a ring associated to the CPSW9G virtual port from user space (A72 core in EL0)? If yes, is there anything needed to be different for TISCI configuration (https://software-dl.ti.com/tisci/esd/latest/2_tisci_msgs/rm/rm_ra.html) or any other way?

What I tried:

* ring accelerator allocated and configured (using kernel space driver)

* re-mapped ring push/pop registers to process address space access for user mode access.

* implemented send and receive functions in user space process

Attempting to push the descriptor to the ring from the user space application results in exception. But it works correctly when the descriptor is pushed in kernel space driver (EL1) using the kernel address space register mapping.

6 months ago

0 Zoltan Laszlo 6 months ago

Prodigy 50 points

My problem looks very similar to the one reported for AM654

https://e2e.ti.com/support/processors-group/processors/f/processors-forum/1292095/tmdx654idkevm-linux-userspace-access-to-am654-ring-accelerator-registers

Unfortunately that thread has no closure.

0 Brijesh Jadav 6 months ago

TI__Guru**** 478015 points

Hi,

Zoltan Laszlo said:
push/pop addresses of a ring associated to the CPSW9

but why do you want to access ring in the user space application?

Regards.,

Brijesh

0 Zoltan Laszlo 6 months ago in reply to Brijesh Jadav

Prodigy 50 points

We want send and receive operations for CPSW9g in user space to complement a full network stack that is in user space. Similar to what a microkernel based OS would do.

0 Brijesh Jadav 6 months ago in reply to Zoltan Laszlo

TI__Guru**** 478015 points

I dont think we have validated accessing ring and other registers from the userspace, it might also not be allowed, and might be firewalled, so instead, can you please send the request to kernel driver and driver should put this request to the ring?

0 Zoltan Laszlo 6 months ago in reply to Brijesh Jadav

Prodigy 50 points

TI provides the J784S4 SDK for QNX. My understanding is that for QNX the CPSW9g network port driver (devnp-cpsw9g.so) is executed in user mode, isn't it? In the SDK, enet_udma.c has some QNX specific parts (ifdefs). The one that especially stood out to me is that it uses the proxy module (pRxFlowPrms->useProxy = true) to access the ring. There is no comment explaining the reason, but I wonder if has anything to do with user space?

Sending the ring request to kernel driver is too high overhead, and severely impacts network stack performance.

0 Zoltan Laszlo 6 months ago in reply to Zoltan Laszlo

Prodigy 50 points

Discussion taken to a private thread. Closing this one.

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J784S4XEVM: Ring Accelerator access from user mode (EL0) on TDA4VH