[broadcom] Trident3-X3 vxlan tunnel/riot enablement prevent SAI initialization on Dell N3248TE

[bradh352]

Description

Trident3 advertises VXLAN support. However Trident3-X3 (aka Helix5) on a Dell N3248TE-ON switch won't allow initialization if flow_init_mode=1 or riot_enable=1 are set in the .bcm initialization/configuration file. This does, however, work on a b87 series Trident3 switch (Dell S5248F).

When evaluating the identification of the chip, such as broadcom common config does, it matches the 'b37' identifier. Looking at the broadcom common config in

sonic-buildimage/device/broadcom/x86_64-broadcom_common/x86_64-broadcom_b37/broadcom-sonic-td3.config.bcm

Lines 3 to 4 in 14cd21f

	flow_init_mode=1
	riot_enable=1

we can see it enables these options by default, so it seems like it is intended that these are supported on this chip.

As the configuration options in this file are publicly undocumented, it is not clear if maybe another option set via the dell configuration (https://github.com/sonic-net/sonic-buildimage/blob/master/device/dell/x86_64-dellemc_n3248te_c3338-r0/DellEMC-N3248TE/hx5-n3248te-48x1G%2B4x10G.config.bcm) is causing a conflict, or if there is some dell-specific firmware change to prevent this from operating for some reason.

The switch is running the latest dell-provided firmware:
https://www.dell.com/support/home/en-ee/drivers/driversdetails?driverid=d8mt0&oscode=naa&productcode=networking-n3200-series

Steps to reproduce the issue:

1. Boot Dell N3248TE-ON switch with SONiC master (or 202411) after editing the /usr/share/sonic/device/x86_64-dellemc_n3248te_c3338-r0/DellEMC-N3248TE/hx5-n3248te-48x1G+4x10G.config.bcm file to include either flow_init_mode=1 or riot_enable=1 and notice SAI initialization fails.

Describe the results you received:

SAI initialization fails

Describe the results you expected:

SAI Initialization succeeds

Output of show version:

202411 or master as of 20241223

Output of show techsupport:

Additional information you deem important (e.g. issue happens only occasionally):

[bradh352]

Ping broadcom contributors on this issue: @Praveen-Brcm @geans-pin @Gfrom2016

[bradh352]

Ping dell contributors on this issue: @arunlk-dell @aravindmani-1 @srideepDell