The Source Policy Management (SPM) on the TPS65988 PD controller operates on the below criteria:

• The SPM is enabled by setting MultiPortSourcePolicy = 1.
• The SPM works only when there is an explicit PD contract or a disconnect on one port while the adjacent port is already in an explicit contract.
• The SPM may affect either port, regardless of the port which triggered a negotiation of PDOs or a disconnect.
• The SPM allows any one port to have a high current contract. It may be triggered by the current port or the adjacent port. The adjacent port would be in a default USB current contract (900 mA).
• The SPM feature is available only for Ice Lake processors, meaning, the TBTControllerType setting should be 0x03. It is not available for other platforms.

SPM Behavior:

As mentioned previously, the SPM feature works only on Ice Lake settings and with the adjacent port already in an explicit PD contract. The behavior is as described below:

• If SPM is triggered by a PDO negotiation on a port:
  • If the present port receives a Request Data Object (RDO) with an operating current above the default USB current (900 mA), the adjacent port's active contract current is lowered to the default USB current and a renegotiation of an explict contract occurs on the Adjacent port.
  • If the RDO current of the present port is already at the default USB current or lesser (based on the Sink's request) or if a GPIO mapped to Prevent High Current Contract Event (#80) is HIGH, the adjacent port's advertised current is restored as per the TX Source Capabilities Register (0x32) settings and a renegotiation of an explict contract occurs on the Adjacent port if SPM had previously restricted its advertisement.
• If a port gets disconnected then SPM will restore the advertised current in adjacent port's TX SourceCapability register and force adjacent port to renegotiate if needed.