Coherency control with writeback ordering
First Claim
1. Interconnect circuitry for a data processing apparatus, said interconnect circuitry being configured to provide routes for interconnecting a plurality of initiator devices and at least one recipient device, at least one of said at least one recipient device comprising at least one memory for storing at least one data item to be processed by said processing apparatus, at least one of said plurality of initiator devices comprising a cache for storing a local copy of a subset of said data items stored in said at least one memory said interconnect circuitry comprising:
- a plurality of input ports for receiving transaction requests from said plurality of initiator devices;
at least one output port for outputting transaction requests to said at least one recipient device;
a plurality of paths for transmitting said transaction requests between said plurality of inputs and said at least one output;
coherency control circuitry for maintaining an order in which at least some of said transaction requests to a same data storage location proceed through said interconnect circuitry in order to maintain coherency of data items processed by said data processing apparatus;
said interconnect circuitry being configured not to control a writeback transaction requests with said coherency control circuitry, such that said writeback transaction requests proceed independently of transaction requests routed through said coherency control circuitry, said writeback transaction requests being write transaction requests received from said at least one initiator device comprising said cache and being for updating said at least one memory with a locally stored updated value of one of said data items.
1 Assignment
0 Petitions
Accused Products
Abstract
Interconnect circuitry configured to provide routes for interconnecting several initiator devices and at least one recipient device including a memory. At least one of the initiator devices has a cache for storing a local copy of a subset of data items stored in the memory. The interconnect circuitry includes: a plurality of input ports and at least one output port; a plurality of paths for transmitting the transaction requests between the inputs and the at least one output; coherency control circuitry for maintaining an order in which at least some of the transaction requests to a same data storage location proceed through the interconnect circuitry. The interconnect circuitry is configured not to control the writeback transaction requests with the coherency control circuitry, such that the writeback transaction requests proceed independently of transaction requests routed through the coherency control circuitry.
-
Citations
21 Claims
-
1. Interconnect circuitry for a data processing apparatus, said interconnect circuitry being configured to provide routes for interconnecting a plurality of initiator devices and at least one recipient device, at least one of said at least one recipient device comprising at least one memory for storing at least one data item to be processed by said processing apparatus, at least one of said plurality of initiator devices comprising a cache for storing a local copy of a subset of said data items stored in said at least one memory said interconnect circuitry comprising:
-
a plurality of input ports for receiving transaction requests from said plurality of initiator devices; at least one output port for outputting transaction requests to said at least one recipient device; a plurality of paths for transmitting said transaction requests between said plurality of inputs and said at least one output; coherency control circuitry for maintaining an order in which at least some of said transaction requests to a same data storage location proceed through said interconnect circuitry in order to maintain coherency of data items processed by said data processing apparatus; said interconnect circuitry being configured not to control a writeback transaction requests with said coherency control circuitry, such that said writeback transaction requests proceed independently of transaction requests routed through said coherency control circuitry, said writeback transaction requests being write transaction requests received from said at least one initiator device comprising said cache and being for updating said at least one memory with a locally stored updated value of one of said data items. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 18, 19, 20)
-
-
15. An initiator device comprising:
-
a cache for storing a local copy of at least one of said data items stored in said memory, said at least one initiator being configured to maintain coherency of said locally stored at least one data item, by in response to said locally stored data item being updated, marking said locally stored data item as dirty until said at least one initiator has performed a writeback operation and written said updated data item to said memory; at least one port for transmitting transaction requests to at least one recipient device, and for receiving data and query requests querying said cache;
whereinsaid initiator device is configured not to issue a response to receipt of a request querying a state of a storage location within said cache if a writeback transaction to said storage location is pending, and to issue said response when said pending writeback transaction has completed, said writeback transaction request being a request issued by said initiator device to update said memory with a value of a data item stored in said cache that has itself been updated, such that said memory stores a current value of said data item. - View Dependent Claims (16, 17)
-
-
21. A method of maintaining coherency comprising the steps of:
-
issuing a writeback request from an initiator comprising a cache to a memory via an interconnect, said writeback transaction request being a write transaction request for updating said memory with an updated value of a data item stored locally on said cache; allowing said writeback request to proceed through said interconnect independently of transaction requests routed through a coherency control circuitry, in response to receipt of a request at said initiator querying a state of a storage location in said cache for which said writeback transaction is pending, not responding to said querying request until said pending writeback transaction has completed.
-
Specification