Create API for fast linkup configuration.

Signed-off-by: Martin Liao <[email protected]>

Author: Martin Liao

doc/SAI-Proposal-Fast-Linkup.md

@@ -0,0 +1,34 @@
+# Fast Link-Up
+-------------------------------------------------------------------------------
+ Title       | Fast Link-Up
+-------------|-----------------------------------------------------------------
+ Authors     | Eddy Kvetny, Nvidia
+ Status      | In review
+ Type        | Standards track
+ Created     | 2025-09-09
+ SAI-Version | 1.17
+-------------------------------------------------------------------------------
+
+# 1. Overview
+In some cases the equalization parameters from the previous session can be used for a new link-up process. It can significantly reduce time of the Link-Up process
+
+# 2. Scope
+This approach is applicable to devices (switch-to-switch or switch-to-NIC) supporting this process, usually from the same vendor or from different vendors aligned on the process
+
+# 3. Architecture
+This feature shall be enabled per-port using a new SAI attribute - SAI_PORT_ATTR_FAST_LINKUP_ENABLED
+
+On ports with the enabled feature the ASIC FW shall try first to bring a link up using the equalization parameter stored from the previous successul session. The time given to ASIC to try to bring a link up with the old EQ parameters is limited by the Fast Link-Up Polling Timer. The time value is configured using a new SAI attribute - SAI_SWITCH_ATTR_FAST_LINKUP_POLLING_TIME. The supported range for this value (in secs) can be read by NOS using a new SAI attribute  SAI_SWITCH_ATTR_FAST_LINKUP_POLLING_TIME_RANGE
+
+If the process of brining a link up with the previosly used EQ parameters doesn't succeed the regular link-up process with new negotiated EQ parameters is triggered
+
+If the link succeeds moving to the Operation UP state then the BER level shall be checked to make sure that the establish link has a good quality. To do that another timer called Guard Timer is used. Its value is also configurable using a new SAI attribute (SAI_SWITCH_ATTR_FAST_LINKUP_GUARD_TIME)
+
+
+When the Guard Timer expires the BER is measured and compared with the "good" BER value configured using a new SAI attribure SAI_SWITCH_ATTR_FAST_LINKUP_BER_THRESHOLD. Only if the measured BER is equal or better than the configured BER threshold the process is considered completed. Otherwise, the fallback to the regular link-up process is done and link's Oper status changes to DOWN
+
+Note that the State Machine is implemented by ASIC FW and can vary between vendors. The proposal just defines just high level flow and SAI configuration for this flow
+
+The following State Machine is proposed for the Fast Link-UP process described above
+
+![](figures/sai_fast_linkup_state_machine.png)

doc/figures/sai_fast_linkup_state_machine.png

@@ -2712,6 +2712,15 @@ typedef enum _sai_port_attr_t
      */
     SAI_PORT_ATTR_PAM4_EYE_VALUES,
 
+    /**
+     * @brief Enables the fast link-up for a port on port/link recovery. Vendors can use to reduce linkup time on remote link failure
+     *
+     * @type bool
+     * @flags CREATE_AND_SET
+     * @default false
+     */
+    SAI_PORT_ATTR_FAST_LINKUP_ENABLED,
+
     /**
      * @brief End of attributes
      */

inc/saiport.h

@@ -3468,6 +3468,57 @@ typedef enum _sai_switch_attr_t
      */
     SAI_SWITCH_ATTR_NEXT_HOP_USER_META_DATA_RANGE,
 
+    /**
+     * @brief Linkup polling time range (in secs)
+     *
+     * @type sai_u16_range_t
+     * @flags READ_ONLY
+     */
+    SAI_SWITCH_ATTR_FAST_LINKUP_POLLING_TIME_RANGE,
+
+    /**
+     * @brief Time (in sec) during which the fast link-up is attempted.
+     *
+     * If this timer expires before the link is UP the regular link-up will be performed
+     * Supported range can be obtained using SAI_SWITCH_ATTR_FAST_LINKUP_POLLING_TIME_RANGE
+     *
+     * @type sai_uint16_t
+     * @flags CREATE_AND_SET
+     * @default 60
+     */
+    SAI_SWITCH_ATTR_FAST_LINKUP_POLLING_TIME,
+
+    /**
+     * @brief Linkup guard time range (in secs)
+     *
+     * @type sai_u16_range_t
+     * @flags READ_ONLY
+     */
+    SAI_SWITCH_ATTR_FAST_LINKUP_GUARD_TIME_RANGE,
+
+    /**
+     * @brief Time (in secs) during which the link must be UP with the BER below the level configured with SAI_SWITCH_ATTR_FAST_LINKUP_GUARD_TIME_BER to keep the fast link-up configuration.
+     *
+     * If either link failures happens within this time or high BER is measured at the end of this period of time the link should undergo regular link up process
+     * Supported range can be obtained using SAI_SWITCH_ATTR_FAST_LINKUP_GUARD_TIME_RANGE
+     *
+     * @type sai_uint8_t
+     * @flags CREATE_AND_SET
+     * @default 10
+     */
+    SAI_SWITCH_ATTR_FAST_LINKUP_GUARD_TIME,
+
+    /**
+     * @brief Configures the BER (negative exponent only, mantissa is always 1) which is if measured during
+     *
+     * SAI_SWITCH_ATTR_FAST_LINKUP_GUARD_TIME causes the full link-up flow. For example, "12" configured here is 1e^-12)
+     *
+     * @type sai_uint8_t
+     * @flags CREATE_AND_SET
+     * @default 12
+     */
+    SAI_SWITCH_ATTR_FAST_LINKUP_BER_THRESHOLD,
+
     /**
      * @brief End of attributes
      */