Abstract: In one embodiment, a cache coherent system includes one or more agents (e.g., coherent agents) that may cache data used by the system. The system may include a point of coherency in a memory controller in the system, and thus the agents may transmit read requests to the memory controller to coherently read data. The point of coherency may determine if the data is cached in another agent, and may transmit a copy back request to the other agent if the other agent has modified the data. The system may include an interconnect between the agents and the memory controller. At a point on the interconnect at which traffic from the agents converges, a copy back response may be converted to a fill for the requesting agent.

Abstract: In one embodiment, a cache coherent system includes one or more agents (e.g., coherent agents) that may cache data used by the system. The system may include a point of coherency in a memory controller in the system, and thus the agents may transmit read requests to the memory controller to coherently read data. The point of coherency may determine if the data is cached in another agent, and may transmit a copy back request to the other agent if the other agent has modified the data. The system may include an interconnect between the agents and the memory controller. At a point on the interconnect at which traffic from the agents converges, a copy back response may be converted to a fill for the requesting agent.

Abstract: In one embodiment, a cache coherent system includes one or more agents (e.g. coherent agents) that may cache data used by the system. The system may include a point of coherency in a memory controller in the system, and thus the agents may transmit read requests to the memory controller to coherently read data. The point of coherency may determine if the data is cached in another agent, and may transmit a copy back request to the other agent if the other agent has modified the data. The system may include an interconnect between the agents and the memory controller. At a point on the interconnect at which traffic from the agents converges, a copy back response may be converted to a fill for the requesting agent.

Abstract: A system and method for efficiently allocating data storage to agents. A computing system includes an interconnect with intermediate buffers for storing transactions and corresponding payload data during transport between sources and destinations. A data storage limit is set on an amount of data storage corresponding to outstanding transactions for each of the multiple sources based on the initial buffer assignments. A number of outstanding transactions for each of the multiple sources is limited based on a corresponding data storage limit. If the rate of allocation of a given buffer assigned to a first source exceeds a threshold, then a second source is selected with available space exceeding a threshold in an assigned buffer. If it is determined the second source is not assigned to a buffer with a rate of allocation exceeding a threshold, then buffer storage is reassigned from the second source to the first source.

Abstract: A system and method for efficiently allocating data storage to agents. A computing system includes an interconnect with intermediate buffers for storing transactions and corresponding payload data during transport between sources and destinations. A data storage limit is set on an amount of data storage corresponding to outstanding transactions for each of the multiple sources based on the initial buffer assignments. A number of outstanding transactions for each of the multiple sources is limited based on a corresponding data storage limit. If the rate of allocation of a given buffer assigned to a first source exceeds a threshold, then a second source is selected with available space exceeding a threshold in an assigned buffer. If it is determined the second source is not assigned to a buffer with a rate of allocation exceeding a threshold, then buffer storage is reassigned from the second source to the first source.

Abstract: A system and method for efficiently routing data in a communication fabric. A computing system includes a fabric for routing data among one or more agents and a memory controller for system memory. The fabric includes multiple hierarchical clusters with a split topology where the data links are physically separated from the control links. A given cluster receives a write command and associated write data, and stores them in respective buffers. The given cluster marks the write command as a candidate to be issued to the memory controller when it is determined the write data will arrive ahead of the write command at the memory controller after being issued. The given cluster prevents the write command from becoming a candidate to be issued when it is determined the write data may not arrive ahead of the write command at the memory controller.

Abstract: Systems and methods for maintaining an order of read and write transactions for each source through a bridge in a bus fabric are disclosed. The bridge provides a connection from a first bus to a second bus within the bus fabric. The first bus has a single path for read and write transactions and the second bus has separate paths for read and write transactions. The bridge allows writes to pass reads for a given source, but prevents reads from passing writes. The bridge forwards a write transaction out of the bridge when the write transaction is available for forwarding. The bridge forwards a read transaction from a given source out of the bridge when there are no outstanding write transactions for the given source that are older than the read transaction. The bridge prevents forwarding the read transaction from the given source out of the bridge when there are outstanding write transactions that are older than the read transaction for the given source.

Abstract: A system and method for efficiently bridging two communication protocols. In various embodiments, a computing system includes an interconnect for routing traffic among agents and endpoints. The agents use a first communication protocol and the endpoints use a second communication protocol that differs from the first protocol with regard to at least the ordering that is enforced between transactions. A bridge selects transactions of a first type and a second type used in the first protocol for processing based on the first protocol ordering while using acknowledgments used by the second protocol.

Abstract: Systems and methods for maintaining an order of read and write transactions for each source through a bridge in a bus fabric are disclosed. The bridge provides a connection from a first bus to a second bus within the bus fabric. The first bus has a single path for read and write transactions and the second bus has separate paths for read and write transactions. The bridge allows writes to pass reads for a given source, but prevents reads from passing writes. The bridge forwards a write transaction out of the bridge when the write transaction is available for forwarding. The bridge forwards a read transaction from a given source out of the bridge when there are no outstanding write transactions for the given source that are older than the read transaction. The bridge prevents forwarding the read transaction from the given source out of the bridge when there are outstanding write transactions that are older than the read transaction for the given source.

Abstract: An apparatus may include first and second clock monitors. The first clock monitor may be configured to receive a first clock signal and assert a first signal if the frequency of the first clock signal is greater than a first upper threshold and assert a second signal if the frequency of the first clock signal is less than a first lower threshold. The second clock monitor may be configured to receive a second clock signal with a frequency higher than that of the first clock signal. The second clock monitor may be configured to compare the second clock signal, dependent upon the first clock signal, to second upper and lower thresholds and assert a third signal if the frequency of the second clock signal is greater than the second upper threshold and assert a fourth signal if the frequency is less than the second lower threshold.

Abstract: An apparatus may include first and second clock monitors. The first clock monitor may be configured to receive a first clock signal and assert a first signal if the frequency of the first clock signal is greater than a first upper threshold and assert a second signal if the frequency of the first clock signal is less than a first lower threshold. The second clock monitor may be configured to receive a second clock signal with a frequency higher than that of the first clock signal. The second clock monitor may be configured to compare the second clock signal, dependent upon the first clock signal, to second upper and lower thresholds and assert a third signal if the frequency of the second clock signal is greater than the second upper threshold and assert a fourth signal if the frequency is less than the second lower threshold.

Abstract: Embodiments of a bridge unit and system are disclosed that may allow for processing fence commands send to multiple bridge units. Each bridge unit may process a respective portion of a plurality of transactions generated by a master unit. The master unit may be configured to send a fence command to each bridge unit, which may stall the processing of the command. Each bridge unit may be configured to determine if all transactions included in its respective portion of the plurality of transactions has completed. Once each bridge unit has determined that all other bridge units have received the fence command and that all other bridge units have completed their respective portions of the plurality of transactions that were received prior to receiving the fence command, all bridge units may execute the fence command.

Abstract: Systems and methods for translating cache hints between different protocols within a SoC. A requesting agent within the SoC generates a first cache hint for a transaction, and the first cache hint is compliant with a first protocol. The first cache hint can be set to a reserved encoding value as defined by the first protocol. Prior to the transaction being sent to the memory subsystem, the first cache hint is translated into a second cache hint. The memory subsystem recognizes cache hints which are compliant with a second protocol, and the second cache hint is compliant with the second protocol.

Abstract: In an embodiment, an arbiter may implement a deficit-weighted round-robin scheme having a delayed weight-reload mechanism. The delay may be greater than or equal to a ratio of the fabric clock to a slower clock associated with one or more sources that have no transactions but that have unconsumed weights (or another measure of difference in transaction rate). If a transaction is provided from the one or more sources during the delay, the reload of the weights may be prevented. In some embodiments, the arbiter may be augmented to improve usage of the bandwidth on an interface in which some transactions may be limited for a period of time. The arbiter may implement a first pointer that performs round robin arbitration. If the first pointer is indicating a source whose transaction is temporarily blocked, a second pointer may search forward from the current position of the main pointer to locate a non-blocked transaction.

Abstract: Various embodiments of a method and apparatus for controlling transaction flow in a communications fabric is disclosed. In one embodiment, an IC includes a communications fabric connecting multiple agents to one another. Each agent may include an interface coupling itself to at least one other agent. Each interface may include multiple queues for storing information corresponding to pending transactions. Also included in each interface is an arbitration unit and control logic. The control logic may determine which transactions are presented to the arbitration unit for arbitration. In one embodiment, the control logic may inhibit certain transactions from being presented to the arbitration unit so that other higher priority transactions may advance. In another embodiment, the control logic may reduce the priority level of some transactions for arbitration purposes to prevent the blocking of other higher priority transactions.

Abstract: Embodiments of a bridge circuit and system are disclosed that may allow converting transactions from one communication protocol to another. The bridge circuit may be coupled to a first bus employing a first communication protocol, and a second bus employing a second communication protocol. The second bus may include a plurality of virtual channels. The bridge circuit may be configured to receive transactions over the first bus, and convert the transactions to the second communication protocol, and to assign the converted transaction to one of the plurality of virtual channels. The bridge circuit may be further configured store the converted transaction. A plurality of limited throughput signals may be generated by the bridge circuit dependent upon a number of available credits for the plurality of virtual channels.

Abstract: Systems and methods for maintaining an order of read and write transactions for each source through a bridge in a bus fabric. The bridge provides a connection from a first bus to a second bus within the bus fabric. The first bus has a single path for read and write transactions and the second bus has separate paths for read and write transactions. The bridge maintains a pair of counters for each source in a SoC to track the numbers of outstanding read and write transactions. The bridge prevents a read transaction from being forwarded to the second bus if the corresponding write counter is non-zero, and the bridge prevents a write transaction from being forwarded to the second bus if the corresponding read counter is non-zero.

Abstract: A method and apparatus for arbitration. In one embodiment, a point in a network includes first and second arbiters. Arbitration of transactions associated with an address within a first range are conducted in the first arbiter, while arbitration of transactions associated with an address within a second range are conducted in the second arbiter. Each transaction is one of a number of different transaction types having a respective priority level. A measurement circuit is coupled to receive information from the first and second arbiters each cycle indicating the type of transactions that won their respective arbitrations. The measurement circuit may update a number of credits associated with the types of winning transactions. The updated number of credits may be provided to both the first and second arbiters, and may be used as a basis for arbitration in the next cycle.

Abstract: In an embodiment, a system includes at least one peripheral device, an interrupt controller, a memory controller, at least one CPU, and an interrupt message circuit coupled to the peripheral device. The interrupt message circuit may be coupled to receive the interrupt signal from the peripheral device, and may be configured to generate an interrupt message for transmission on a communication fabric. In some embodiments, there may be multiple peripherals which have independent paths through the fabric for memory operations to the memory controller. Each such peripheral may be coupled to an instance of the interrupt message circuit. In an embodiment, the interrupt is level sensitive. The interrupt message circuit may be configured to transmit interrupt set messages an interrupt clear messages to the interrupt controller, to indicate the levels.

Abstract: Embodiments of a bridge circuit and system are disclosed that may allow for converting transactions from one communication protocol to another. The bridge circuit may be coupled to a first bus employing a first communication protocol, and a second bus employing a second communication protocol. The bridge circuit may be configured to convert transactions from the first communication protocol to the second communication protocol, and convert transaction from the second communication protocol to the first communication protocol. In one embodiment, the bridge circuit may be further configured to flag transactions that cannot be converted from the second communication protocol to the first communication protocol. In a further embodiment, an error circuit coupled to the bridge circuit may be configured to detect flagged transactions.