Changeset 11354:81cb93c4a16c

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mem: Add unified queue to DRAMCtrl
Add optional unified queue to the DRAMCtrl to serve as a front end queue for

flow control. This prevents needing individual flow control for both read and

write queues by exposing only one queue at the slave side. This makes flow

control more generic and simplistic.
Requests are placed in the unified queue and remain there until a response

is sent back to the requestor. A logical unified queue is represented by

the union of unifiedQueue and unifiedPending. unifiedPending is used for

requests that have already been issued to the memory core and is useful for

reducing the complexity of searching for unissued requests in unifiedQueue.

The size of the unified queue as well as the number of requests that can be

searched in a given cycle can be configured in DRAMCtrl parameters. It can be

disabled altogether (and is by default) by setting use_unified_buffer False

to default to normal behavior in gem5.