Abstract: An interface comprises routing circuitry configured to receive data items from a data source device and to route the received data items to a data sink device by either a first data path including a data buffer or a second data path, in response to an indication of a current state of a data sink device; the routing circuitry being configured to route the received data item by the first data path and to initiate a transition of the data sink device to a ready state in response to an indication that the data sink device is in a quiescent mode and currently not ready to receive the data item, the routing circuitry being configured to hold the data item at the buffer and to inhibit the data source device from sending further data items until the routing circuitry receives a subsequent indication that the data sink device is ready to receive the data item; and the routing circuitry being configured to route the received data item by the second data path in response to an indication that the data sink device is cur

Abstract: A data processing apparatus 2 includes a plurality of power domains controlled by respective power control signals PCS. Power control circuitry 22 includes mapping circuitry which maps a plurality of power status signals PSS indicative of the power status of respective power domains, and received from those power domains, to form the power control signals which are then supplied power domains. The mapping circuitry may be controlled by mapping parameters stored within a memory mapped array. The mapping parameters may specify that a given power control signal is either sensitive or insensitive to the power status of a particular other power domain within the data processing apparatus 2. The mapping parameters may be fixed or software programmable.

Abstract: An apparatus and a corresponding method of operating the apparatus are disclosed. A component of the apparatus is capable of operating in one of at least two power modes and component power control circuitry which is communicatively coupled to the component causes the component to operate in a selected power mode of those power modes. A system power controller controls operation of the component power control circuitry by setting a power mode lock condition therein. When the power mode lock condition is met the component power control circuitry cannot change the selected power mode of the component. Power control over the component is thus partially delegated from the system power controller to the component power control circuitry.

Abstract: Various implementations described herein are directed to a method and apparatus for a low power interface combiner for controlling a cross domain component in a system of two or more power domain controls. The combiner may include a first state for requesting cross domain component quiescence when a first control requests quiescence and a second state for ensuring cross domain component quiescence before accepting the first control quiescence request. The combiner may include a third state for requesting cross domain component quiescence exit when a last control requests quiescence exit and other controls have exited or are exiting quiescence. The combiner may include a fourth state for ensuring cross domain component quiescence exit before accepting the last control quiescence exit request.

Abstract: A method, system, and device provide for selective control in a distributed cache system of the power state of a number of receiver partitions arranged in one or more partition groups. A power control element coupled to one or more of the receiver partitions and a coherent interconnect selectively control transition from a current power state to a new power state by each receiver partition of one or more partition groups of the plurality of partition groups.

Abstract: There is provided a data processing device including an output port to transmit a request value to an interconnect arranged to implement a coherency protocol, to indicate a request to be subjected to the coherency protocol. An input port receives an acknowledgement value from the interconnect in response to the request value and coherency administration circuitry defines behaviour rules for the data processing device in accordance with the coherency protocol and in dependence on the request value and the acknowledgement value. Storage circuitry administers data in accordance with the behaviour rules. There is also provided an interconnect including an input port to receive a request value, issued by a data processing device having storage circuitry, to indicate a request for the data processing to be subjected to a coherency protocol.

Abstract: A data processing apparatus has a cache having a normal mode and a retention mode in which the cache consumes less power than in the normal mode. An interconnect receives, from at least one other device, coherency access requests for data stored in the cache. In the normal mode, the data in the cache is accessible and the cache generates coherency responses in response to the coherency access requests, while in the retention mode the data is retained in the cache but inaccessible in response to the coherency access requests. A coherency controller is provided to monitor the coherency access requests and coherency responses. Switching of the cache from the normal mode to the retention mode is deferred until the coherency controller has detected coherency responses for all coherency access requests passed to said cache.