AM4376: PRP port swap issue

Hi,

The person who can answer this is currently out of office, so response will be delayed for a few days. Sorry for the inconvenience.

Alexey,

Unlike HSR, in the case of PRP there is no frame forwarded from port to port. I might not quite follow you, what happens if you simply swap the cables of Port A (LAN A) and Port B (LAN B) without any TX/RX CFG register change?

Regards,

Garrett

Garrett,

If cables of Port A and Port B are swaped PRP host (Cortex-A9) receives doubled (dublicated) traffic (offload does not take place) and CPU load become critical. It's look like PRP firmware does not apply duplicate discard procedure to packet from other port.

Thanks,

Alexey.

Alexey,

Actually PRP firmware on PRU0 and PRU 1 has the exactly symmetrical function with the exception that initialization and host duplicate check task are only performed by PRU0.

Regards,
Garrett

Garrett,

Our main goal is to swap ports A and port B for both PRP and HSR without the PCB redesign.

According to FAQ section http://software-dl.ti.com/processor-sdk-linux/esd/docs/latest/linux/Industrial_Protocols_HSR_PRP.html#plsdk-hsr-prp-testing-firmware-offload :

In ICSS firmware, PRU-0 is assumed to be for Link-A and PRU-1 for Link-B
of a LRE in the case DANP. So in PRP case, Link-A should be connected network A
and Link-B should be connected to Network B of a PRP network since net-id has to
match as per duplicate detect alogrithm. If this convention is not followed,
duplicate detection logic fails and duplicates are sent to upper layer causing ping
application to complain about duplicates. So when creating prp interface, make sure
ip link command parameter slave 1 use linux interface associated with PRU-0 and
slave 2 use interface associated with PRU-1. Also when making network connection
make sure that PRU-0 port is connected to Network A and PRU-1 port to Network B.

So it seems PRU-0 assumes to be connected to Link-A and we need the physical link currently associated with it to connect to Link-B.

Alexey,

I was out of office for a couple of days, will be discussing with team for the issue you observed.

Thanks,

Garrett

Garrett,

Any update?

Best regards,
Alexander

Hi Alexander,

I brought up the topic but didn't get a definitive answer yet, let me follow up again...

Regards,

Garrett

Hi Alexander,

Have you tried the following configuration for TXCFG:

PRU1 to transmit over Port0 => TX_MUX_SEL = 1 in TXCFG0

PRU0 to transmit over Port1  => TX_MUX_SEL = 0 in TXCFG1

TX_CFG0 is for Port0 and TX_CFG1 is for Port1. Unlike RX CFG which is based on PRUs, TX CFG is based on Ports.

Regards,
Garrett

Hi Garrett,

Yes, we tried configuration when PRU1 transmits over Port0, PRU0 transmits over Port1 - it does works. This is default configuration for PRP (ICSS_EMAC_MODE_SWITCH is used).

To swap LAN_A and LAN_B in PRP we set TX_MUX_SEL = 0 in TXCFG0, TX_MUX_SEL = 1 in TXCFG1 (PRU0 -> Port0, PRU1 -> Port1) - it does not work (no outgoing packets or episodical).

Regards,

Alexey.

Alexey.

Did you try the following configuration:

RX_MUX_SEL = 1 in RXCFG0, RX_MUX_SEL = 0 in RXCFG1

and

TX_MUX_SEL = 1 in TXCFG0, TX_MUX_SEL = 0 in TXCFG1

Regards,
Garrett

Garrett,

Yes, we tried RX_MUX_SEL = 1 in RXCFG0, RX_MUX_SEL = 0 in RXCFG1, TX_MUX_SEL = 1 in TXCFG0, TX_MUX_SEL = 0 in TXCFG1 configuration.

PRP case: on Rx path we got desired result, on Tx path (without any HSR/PRP driver changes) Port0 outgoing packets are marked as LAN A, Port1 outgoing packets are marked as LAN B.

HSR case: as I understand, cut-through is impossible at this configuration. So we didn't try it for HSR.

Regards,

Alexey.

Hi Alexey,

I have been out of office and will return 2 weeks later to continue to look into this...

Regards,

Garrett

Alexey,

Is the issue still pending or you have figured out the configuration?

Regards,

Garrett

Hi Alexey,

Thanks for the update! Would you please elaborate how this was resolve? It would be beneficial for other users who might run into the problem as well......

Regards,
Garrett

Garrett,

For PRP:

1. RX_MUX_SEL = 1 in RXCFG0, RX_MUX_SEL = 0 in RXCFG1, TX_MUX_SEL = 1 in TXCFG0, TX_MUX_SEL = 0 in TXCFG1 configuration is used (MII_RT registers).

2. HSR/PRP driver changes. In hsrPrp_red.c file change port argument of "RedTxPacketEnqueue" function call: for LAN A to ICSS_EMAC_PORT_2, for LAN B to ICSS_EMAC_PORT_1.

For HSR:

1. used default (as for switch) configuration of RXCFGx, TXCFGx

2. same as for PRP

As result Port0 is LAN B, Port1 is LAN A.

Regards,

Alexey.

Thanks for your input Alexey! I am closing the thread...

Regards,
Garrett