Protocol Level Control for System on a Chip (SOC) Agent Reset and Power Management

Abstract

A system for consistently implementing reset and power management of IP agents on a System on a Chip (SoC). When IP agents undergo a reset, an individual negotiation takes placed between an interconnect and each IP agent over a link. Each IP agent can emerge from reset at its own time schedule, independently of the timing of the other IP agents. The interconnect may be configured as a proxy for any IP agent that is inoperable, including prior to reset, when in a power-down mode, or malfunctioning.

What is claimed is: 
     
         1 . A System on a Chip (SoC), comprising:
 a plurality of IP agents;   an interconnect arranged to handle transactional traffic between the plurality of IP agents, the interconnect including a first port and a second port;   a first IP agent of the plurality of IP agents, the first IP agent configured to communicate with the interconnect using a first link, the first link directly connecting the first IP agent to the first port;   a second IP agent of the plurality of IP agents, the second IP agent configured to communicate with the interconnect using a second link, the second link directly connecting the second IP agent to the second port;   a reset manager configured to:
 enable the first IP agent and the second IP agent to become transaction-ready independent of one another, the enabling involving individual reset negotiations including a first reset negotiation over the first link and between the first port and the first IP agent, the first reset negotiation comprising:
 determining that the first IP agent is capable of sending transactions or processing received transactions; 
 responsive to determining that the first IP agent is capable of sending transactions or processing received transactions, exchanging information over the first link, the information including an amount of data capable of being transmitted over the first link; and 
 responsive to exchanging the information including the amount of data capable of being transmitted over the first link, enabling the first IP agent to receive incoming transactions from the interconnect or send outgoing transactions over the interconnect. 
 
   
     
     
         2 . The SoC of  claim 1 , wherein:
 the link directly connects the first IP agent to the first port without intermediate circuitry; and   the reset negotiation does not require intermediate circuitry between the first IP agent and the first port.   
     
     
         3 . The SoC of  claim 1 , wherein:
 the reset manager individually initiates a reset of the first IP agent in response to a reset trigger event, the first reset negotiation being responsive to the reset of the first IP agent, the reset trigger event including at least one of the following:
 an emergence of the SoC from reset; or 
 a command to reset the first IP agent. 
   
     
     
         4 . The SoC of  claim 1 , wherein:
 the individual reset negotiations include a second reset negotiation over the second link and between the second port and the second IP agent.   
     
     
         5 . The SoC of  claim 4 , wherein:
 the first reset negotiation enables the first IP agent to become transaction-ready on a first clock cycle; and   the second reset negotiation enables the second IP agent to become transaction ready on a second clock cycle different from the first clock cycle.   
     
     
         6 . The SoC of  claim 4 , wherein:
 the first reset negotiation and the second reset negotiation include a same set of negotiations, the same set of negotiations occurring between the first port and the first IP agent and the second port and the second IP agent, respectively.   
     
     
         7 . The SoC of  claim 4 , wherein:
 the first reset negotiation and the second reset negotiation are responsive to a first reset of the first IP agent and a second reset of the second IP agent, respectively, the first reset and the second reset being individual reset routines distinct from one another.   
     
     
         8 . The SoC of  claim 1 , wherein the first individual reset negotiation is conducted using link-level information that is directly transmitted over the first link between the first port and the first IP agent, the direct transmission not sent to another destination and unmodified by the first link, the other destination distinct from the first IP agent and the first port. 
     
     
         9 . The SoC of  claim 1 , wherein the first reset negotiation further comprises the interconnect transmitting a plurality of inquiries to determine that the first IP agent is capable of sending transactions or processing received transactions, the plurality of inquiries sent by the interconnect using the first link at periodic intervals respectively. 
     
     
         10 . The SoC of  claim 9 , wherein:
 the first reset negotiation further comprises the first IP agent transmitting signaling to the interconnect in response to receiving one or more of the plurality of inquiries from the interconnect; and   determining that the first IP agent is capable of sending transactions or processing received transactions is responsive to the first IP agent transmitting the signaling to the interconnect.   
     
     
         11 . The SoC of  claim 1 , wherein the first reset negotiation further comprises the first port and the first IP agent exchanging security information. 
     
     
         12 . The SoC of  claim 1 , wherein the first reset negotiation further comprises the first port exchanging an agreed upon number of virtual channels to be associated with the first link, the first link associated with one or more virtual channels, the one or more virtual channels comprising:
 independent streams of information for respective virtual channels; and   assigned priorities for the respective virtual channels, the assigned priorities at least including a higher priority enabling a virtual channel of the one or more virtual channels to have greater arbitrated access to the interconnect when compared to another virtual channel of a lower priority.   
     
     
         13 . The SoC of  claim 1 , wherein:
 the first IP agent and the second IP agent comprise different circuitry; and   the first link and the second link comprise a same circuitry.   
     
     
         14 . A method comprising:
 enabling a first IP agent and a second IP agent of a plurality of IP agents to become transaction-ready independent of one another, the first IP agent and the second IP agent communicatively coupled to an interconnect at a first port and a second port, respectively, through a first link and a second link, respectively, the enabling involving individual reset negotiations including a first reset negotiation over the first link and between the first port and the first IP agent, the first reset negotiation comprising:
 determining that the first IP agent is capable of sending transactions or processing received transactions; 
 responsive to determining that the first IP agent is capable of sending transactions or processing received transactions, exchanging information over the first link, the information including an amount of data capable of being transmitted over the first link; and 
 responsive to exchanging the information including the amount of data capable of being transmitted over the first link, enabling the first IP agent to receive incoming transactions from the interconnect or send outgoing transactions over the interconnect. 
   
     
     
         15 . The method of  claim 14 , wherein the individual reset negotiations include a second reset negotiation over the second link and between the second port and the second IP agent. 
     
     
         16 . The method of  claim 15 , wherein:
 the first reset negotiation enables the first IP agent to become transaction-ready on a first clock cycle; and   the second reset negotiation enables the second IP agent to become transaction ready on a second clock cycle different from the first clock cycle.   
     
     
         17 . The method of  claim 15 , wherein:
 the first reset negotiation and the second reset negotiation include a same set of negotiations, the same set of negotiations occurring between the first port and the first IP agent and the second port and the second agent, respectively.   
     
     
         18 . The method of  claim 15 , wherein:
 the first reset negotiation and the second reset negotiation are responsive to a first reset of the first IP agent and a second reset of the second IP agent, respectively, the first reset and the second reset being individual reset routines distinct from one another.   
     
     
         19 . The method of  claim 14 , wherein the first reset negotiation further comprises the first port and the first IP agent exchanging security information. 
     
     
         20 . The method of  claim 14 , wherein the first reset negotiation further comprises the first port exchanging an agreed upon number of virtual channels to be associated with the first link, the first link associated with one or more virtual channels, the one or more virtual channels comprising:
 independent streams of information for respective virtual channels; and   assigned priorities for the respective virtual channels, the assigned priorities at least including a higher priority enabling a virtual channel of the one or more virtual channels to have greater arbitrated access to the interconnect when compared to another virtual channel of a lower priority.