AM6548: PRU as store and forward switch

Hanno Reimer

Part Number: AM6548

We noticed during the evaluation of AM65xx that the PRU ICSSG's of the AM6548 "ONLY" are used as 2 Port CUT Through Switches (or Dual MAC). (At least with firmware included on TI-RTOS PDK ).

In our designs, however, we currently only use 3-6-port store and forward switches. (One or two ports are occupied by the host).

Is it possible to use the PRU-ICSSG‘s as store and forward switches ?

I suspect the 2-port switch is derived from the structure of the PRU-ICSSG (PRU0, PRU1) and cannot be extended to additional ports. In addition, the available data RAM 0-2 is likely to be quite tight, as the frames are for a store and forward switch must be cached before it is shared. In this case, we would have to provide an external switch in our design.

Do you agree with me or do you see a solution based on the PRUs within the Sitara for our project ?

Thanks and bye

Hanno

over 1 year ago

0 Nick Saulnier over 1 year ago

TI__Guru* 79035 points

Hello Hanno,

I am not familiar with a "store and forward" option on our devices for more than a single PRU_ICSSG instance. As far as I am aware, a Ethernet packet coming into port X on one PRU_ICSSG would need to get passed through the controlling core (A53 or R5) before it could be sent out of a port on a different PRU_ICSSG (where each PRU_ICSSG instance can have two external ports). I assume this is what you mean when you say "3-6-port store and forward switches"

Let me do some digging to see if this was ever implemented - it looks like we at least considered the usecase in the past, as described here: https://e2e.ti.com/support/processors-group/processors/f/processors-forum/820083/rtos-am5728-4-port-store-and-forward-switch-by-using-2-x-dual-emac-switch-of-am57xx

Feel free to ping the thread if I have not responded within a couple of days.

Regards,

Nick

0 Nick Saulnier over 1 year ago in reply to Nick Saulnier

TI__Guru* 79035 points

Hello Hanno,

Summary

A 3-6 port Ethernet switch with multiple PRU_ICSSG instances is not a usecase we have investigated or written code for that this point in time.

Other details

The thread I linked to was never implemented. From the ticket that was mentioned:

"The request here is to implement a 4 Port Switch using 2xICSS_M IIUC. This implies software switching between 2 ports of ICSS_M with other using SoC DMA or other means. So this requires detailed analysis for performance study prior to making any commitments"

The team did not have the resources to do the performance study & development on the AM57xx, so the request was rejected.

Regards,

Nick

0 Krishna Nagarajan over 1 year ago in reply to Nick Saulnier

Prodigy 250 points

Hi Nick,

We have implemented the 5-Port Switch using 2xICSS_M on the AM57x. The details are available here: https://www.couthit.com/portfolio/5-port-industrial-ethernet-switch/

The 5-Port Switch on the AM572x is Profinet conformance tested and has been deployed on the field.

Further, the 5-Port Switch can also be customized to work as two 3-Port Ethernet Switch, with the ARM host core being the common port.

Hi Hanno,

We have the expertise of developing the 5-Port Switch on the AM57x. We are also fully familiar with the ICSSG architecture and can help with the development of a 6-Port store-and-forward switch on the AM65x platform. Please feel free to contact us if you have any questions or need more information.

Thanks, Krishna

0 Nick Saulnier over 1 year ago in reply to Krishna Nagarajan

TI__Guru* 79035 points

Thanks for responding Krishna!

0 Pekka Varis 8 months ago in reply to Nick Saulnier

TI__Mastermind 23520 points

We now have ARM processor with 4 and 8-port hardware Ethernet switch parts available, https://www.ti.com/product/DRA821U (4 ports) and https://www.ti.com/product/AM69 (8 ports).

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AM6548: PRU as store and forward switch