[Test Gap][RDMA][T0/T1/BET0/BET1] PFC stuck in backpressure state for TD2 devices when PFCWD is triggered

[developfast]

Test Gap Description

A BCM SAI bug on TD2 platforms related to PFCWD causes the PFC backpressure bit to be stuck in backpressure state, after PFCWD has been triggered and reset resulting in the device sending peer devices constant PFC pause frames, causing congestion in the whole network.

Test Plan

Using ptf,

1. Flood PFC pause frames (PFC storm) on priorities 3 and 4 simultaneously to trigger PFCWD.
2. Trigger data flow through this interface, note that packets get dropped.
3. Stop PFC storm on the interface
4. Check MMU registers to see PFC backpressure state and ensure it is 0.
5. Continue sending data traffic, and see that packets are not dropped now.
6. Ensure device stops sending PFC pause frames to egress ptf port.

Test environment

All TD2 devices

Attach files (if any)

No response