SAI switch attribute to enable PTP on all ports

Signed-off-by: Rich Sugarman <rsugarman@nvidia.com>

Author: rdsugarmannv

doc/SAI-Proposal-Global-PTP-Configuration.md

@@ -0,0 +1,88 @@
+# Global PTP Configuration in SAI Switch
+
+Title       | Global PTP Configuration in SAI Switch
+------------|----------------------------------------
+Authors     | Open
+Status      | Draft
+Type        | Standards track
+Created     | 2024-03-03
+SAI-Version | 1.15
+
+## Overview
+Introducing a PTP (Precision Time Protocol) attribute to the SAI switch object, allowing for switch-wide PTP mode settings that affect all ports on the switch. 
+
+A switch that does not set this attribute will observe no change in behavior.
+
+## Motivation
+Currently, PTP configuration in SAI is port-based, and many switches only support configuration of PTP on a global basis.
+In addition, many existing switches have a configuration model which allows global configuration of PTP, and then override on a port level.  SAI should follow this flexible example.
+
+## Technical Specification
+
+### Updated description of existing PORT PTP type - the main comment is new
+```c
+/**
+ * @brief PTP mode
+ * 
+ * These modes can be used at the port and switch level.
+ * All ports use the value set at the switch level unless explicitly configured
+ * at the port level to a value other than SAI_PORT_PTP_MODE_NONE.
+ */
+typedef enum _sai_port_ptp_mode_t
+{
+    /** No special processing for PTP packets */
+    SAI_PORT_PTP_MODE_NONE,
+
+    /** Single-step Timestamp mode for the PTP packets */
+    SAI_PORT_PTP_MODE_SINGLE_STEP_TIMESTAMP,
+
+    /** Two-step Timestamp mode for the PTP packets */
+    SAI_PORT_PTP_MODE_TWO_STEP_TIMESTAMP,
+
+} sai_port_ptp_mode_t;
+
+
+### New Switch Attribute
+```c
+typedef enum _sai_switch_attr_t
+{
+    // ... existing attributes ...
+
+    /**
+     * @brief Global PTP mode configuration
+     *
+     * Global PTP mode configuration for the switch.
+     * Applies to all ports unless overridden by port-specific settings.
+     *
+     * @type sai_port_ptp_mode_t
+     * @flags CREATE_AND_SET
+     * @default SAI_PORT_PTP_MODE_NONE
+     */
+    SAI_SWITCH_ATTR_PORT_PTP_MODE,
+
+    // ... existing attributes ...
+} sai_switch_attr_t;
+```
+
+## Usage Example
+```c
+// Set global PTP configuration at switch level
+sai_attribute_t attr;
+attr.id = SAI_SWITCH_ATTR_PORT_PTP_MODE;
+attr.value.s32 = SAI_PORT_PTP_MODE_SINGLE_STEP_TIMESTAMP;
+
+sai_status_t status = sai_switch_api->set_switch_attribute(
+    switch_id,
+    &attr);
+
+// Get global PTP configuration
+attr.id = SAI_SWITCH_ATTR_PORT_PTP_MODE;
+status = sai_switch_api->get_switch_attribute(
+    switch_id,
+    1,
+    &attr);
+```
+
+## References
+1. IEEE 1588-2008 Standard for a Precision Clock Synchronization Protocol for Networked Measurement and Control Systems
+2. IEEE 1588-2019 Standard for a Precision Clock Synchronization Protocol for Networked Measurement and Control Systems 

inc/saiport.h

@@ -395,6 +395,9 @@ typedef enum _sai_port_priority_flow_control_mode_t
 
 /**
  * @brief PTP mode
+ * These modes can be used at the port and switch level.
+ * All ports use the value set at the switch level unless explicitly configured
+ * at the port level to a value other than SAI_PORT_PTP_MODE_NONE.
  */
 typedef enum _sai_port_ptp_mode_t
 {

inc/saiswitch.h

@@ -3197,6 +3197,18 @@ typedef enum _sai_switch_attr_t
      */
     SAI_SWITCH_ATTR_SHARED_BUFFER_CELL_SIZE,
 
+    /**
+     * @brief Global PTP mode configuration
+     *
+     * Global PTP mode configuration for the switch.
+     * Applies to all ports unless overridden by port-specific settings.
+     *
+     * @type sai_port_ptp_mode_t
+     * @flags CREATE_AND_SET
+     * @default SAI_PORT_PTP_MODE_NONE
+     */
+    SAI_SWITCH_ATTR_PORT_PTP_MODE,
+
     /**
      * @brief End of attributes
      */