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sonic-net · Jan 22, 2022 · d9d1ba6 · d9d1ba6
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diff --git a/doc/sfp-cmis/Interface-Link-bring-up-sequence.md b/doc/sfp-cmis/Interface-Link-bring-up-sequence.md
@@ -2,7 +2,7 @@
 Deterministic Approach for Interface Link bring-up sequence
 
 # High Level Design Document
-#### Rev 0.2
+#### Rev 0.3
 
 # Table of Contents
   * [List of Tables](#list-of-tables)
@@ -25,7 +25,7 @@ Deterministic Approach for Interface Link bring-up sequence
 |:---:|:-----------:|:----------------------------------:|------------------------------|
 | 0.1 | 08/16/2021  | Shyam Kumar                        | Initial version                       
 | 0.2 | 12/13/2021  | Shyam Kumar,  Jaganathan Anbalagan | Added uses-cases, workflows  
-| 0.3 | 01/19/2022  | Shyam Kumar                        | Addressed review-comments    |
+| 0.3 | 01/19/2022  | Shyam Kumar,  Jaganathan Anbalagan | Addressed review-comments    |
 
 
 # About this Manual
@@ -56,22 +56,22 @@ Interface link bring-up sequence and workflows for use-cases around it
 
 # Problem Definition
 
-1.	Presently in SONiC, there is no synchronization between 400G Datapath Init operation and enabling ASIC (NPU/PHY) Tx which may cause link instability during administrative interface enable “config interface startup Ethernet” configuration and bootup scenarios. 
+1.	Presently in SONiC, there is no synchronization between Datapath Init operation of CMIS complaint optical module and enabling ASIC (NPU/PHY) Tx which may cause link instability during administrative interface enable “config interface startup Ethernet” configuration and bootup scenarios. 
 
-    For 400G optics module, the Host (NPU/PHY) needs to provide a valid high-speed Tx input signal at the required signaling rate and encoding type prior to causing a DPSM to exit from DPDeactivated state and to move to DP Init transient state.
+    For CMIS-compliant active (optical) modules, the Host (NPU/PHY) needs to provide a valid high-speed Tx input signal at the required signaling rate and encoding type prior to causing a DPSM to exit from DPDeactivated state and to move to DP Init transient state.
 
     Fundamentally it means - have a deterministic approach to bring-up the interface.
 
     Also, this problem is mentioned ‘as outside-the-scope’ of ‘CMIS Application Initialization’ high-level design document
       **(https://github.com/ds952811/SONiC/blob/0e4516d7bf707a36127438c7f2fa9cc2b504298e/doc/sfp-cmis/cmis-init.md#outside-the-scope)**
 
-2.  During administrative interface disable “config interface shutdown Ethernet”, only the ASIC(NPU) Tx is disabled and not the optics laser for 100G/400G. 
+2.  During administrative interface disable “config interface shutdown Ethernet”, only the ASIC(NPU) Tx is disabled and not the opticcal module Tx/laser. 
       This will lead to power wastage and un-necessary fan power consumption to keep the module temperature in operating range 
 
 # Background
 
-  Per the ‘QSFPDD spec’,  ‘validation, diagnostics’ done by HW team' and 'agreement with vendors', 
-  need to follow following bring-up seq to enable port/interface with 400G optics in LC/chassis:
+  Per the ‘CMIS spec’,  ‘validation, diagnostics’ done by HW team' and 'agreement with vendors', 
+  need to follow following bring-up seq to enable port/interface with CMIS compliant optical modules in LC/chassis:
 
     a) Enable port on NPU (bring-up port, serdes on the NPU ; enable signals) : syncd
     b) Enable port on PHY (bring-up port, serdes on the PHY ; enable signals) : gbsyncd
@@ -80,14 +80,14 @@ Interface link bring-up sequence and workflows for use-cases around it
 
   In boards not having PHY, #b) not needed but #a) and #c) sequence to be followed.
 
-  ## Clause from QSFP-DD (CMIS4.0 spec)
+  ## Clause from CMIS4.0 spec
 
      Excerpt from CMIS4.0 spec providing detailed reasoning for the above-mentioned bring-up sequence
      
   ![61f5b485-cf3b-4ca8-beac-9102b6feabfe](https://user-images.githubusercontent.com/69485234/147173702-f124fc9d-ef27-4816-b1a1-b4a44a5833a7.PNG)
 
 
-  ## Clause from QSFP-DD (CMIS5.0 spec)
+  ## Clause from CMIS5.0 spec
 
      Excerpt from CMIS5.0 spec providing detailed reasoning for the above-mentioned bring-up sequence
      
@@ -96,26 +96,27 @@ Interface link bring-up sequence and workflows for use-cases around it
 
 # Objective
 
-Have a determistic approach for Interface link bring-up sequence i.e. below sequence to be followed:
+Have a determistic approach for Interface link bring-up sequence for all interfaces types i.e. below sequence to be followed:
   1. Initialize and enable NPU Tx and Rx path
   2. For system with 'External' PHY: Initialize and enable PHY Tx and Rx on both line and host sides; ensure host side link is up 
-  3. Then only perform optics data path initialization/activation/Tx enable (for CMIS complaint optical modules) and Tx enable (for SFF complaint optical modules) 
+  3. Then only perform optics data path initialization/activation/Tx enable (for CMIS complaint optical modules) and Tx enable (for SFF complaint optical modules)
 
 # Proposal
 
 Recommend following this high-level work-flow sequence to accomplish the Objective:
 - xcvrd to subscribe to a new field “host_tx_ready” in port table state-DB
 - Orchagent will set the “host_tx_ready” to true/false based on the SET_ADMIN_STATE attribute return status to syncd/gbsyncd. (As part of SET_ADMIN_STATE attribute enable, the NPU Tx is enabled)
 - xcvrd process the “host_tx_ready” value change event and do optics datapath init / de-init using CMIS API
-- Recommendation is to follow this proposal for all the known interfaces - 400G/100G/40G/25G/10G. Reason being: 
-  - 400G - as mentioned above the CMIS spec to be followed
-  - 100G/40G/25G/10G - 
+- Recommendation is to follow this proposal for all the known interfaces types- 400G/100G/40G/25G/10G. Reason being: 
+  - CMIS complaint optical modules:-
+      All CMIS complaint optical modules will follow this approach as recommended in the CMIS spec.
+  - SFF complaint optical modules:- 
     - deterministic approach to bring the interface will eliminate any link stability issue which will be difficult to chase in the production network
       e.g. If there is a PHY device in between, and this 'deterministic approach' is not followed, PHY may adapt to a bad signal or interface flaps may occur when the optics tx/rx  enabled during PHY initialization. 
     - there is a possibility of interface link flaps with non-quiescent optical modules <QSFP+/SFP28/SFP+> if this 'deterministic approach' is not followed
     - It helps bring down the optical module laser when interface is adminstiratively shutdown. Per the workflow here, this is acheived by xcvrd listening to host_tx_ready field from PORT_TABLE of STATE_DB. Turning the laser off would reduce the power consumption and avoid any lab hazard
-    - Additionally provides uniform workflow (from SONiC NOS) across all interface types instead of just 400G
-  - This synchronization will also benefit native 10G SFPs interfaces as they are "plug N play" and may not have quiescent functionality. (xcvrd can use the optional 'soft tx disable' ctrl reg to disable the tx)
+    - Additionally provides uniform workflow (from SONiC NOS) across all interface types with or without module presence. 
+  - This synchronization will also benefit SFP+ optical modules as they are "plug N play" and may not have quiescent functionality. (xcvrd can use the optional 'soft tx disable' ctrl reg to disable the tx)
 
 # Proposed Work-Flows
 Please refer to the  flow/sequence diagrams which covers the following required use-cases
@@ -142,7 +143,7 @@ Please refer to the  flow/sequence diagrams which covers the following required
 Following items are not in the scope of this document. They would be taken up separately
 1. xcvrd restart 
    - If the xcvrd goes for restart, then all the DB events will be replayed. 
-     Here the Datapath init/activate (for 400G), tx-disable register set (for 100G), will be a no-op if the optics is already in that state 
+     Here the Datapath init/activate for CMIS compliant optical modules, tx-disable register set (for SFF complaint optical modules), will be a no-op if the optics is already in that state 
 2. syncd/gbsyncd/swss docker container restart
    - Cleanup scenario - the host_tx_ready field in STATE-DB should be updated to “False” to respective ports that a PHY/NPU interface with
 3. CMIS API feature is not part of this design and the APIs will be used in this design. For CMIS HLD, Please refer to: