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authorWendy Elsasser <wendy.elsasser@arm.com>2016-10-13 19:22:11 +0100
committerWendy Elsasser <wendy.elsasser@arm.com>2016-10-13 19:22:11 +0100
commit1dc16aff247416bb077878160961ff71c285daee (patch)
tree3ad9fdff41da399ca3d74635bb934168bea6a2e7 /src/mem/DRAMCtrl.py
parent7b269f2c95f546e69b5f5bea0edc741f2a0d9cfe (diff)
downloadgem5-1dc16aff247416bb077878160961ff71c285daee.tar.xz
mem: Add DRAM low-power functionality
Added power-down state transitions to the DRAM controller model. Added per rank parameter, outstandingEvents, which tracks the number of outstanding command events and is used to determine when the controller should transition to a low power state. The controller will only transition when there are no outstanding events scheduled and the number of command entries for the given rank is 0. The outstandingEvents parameter is incremented for every RD/WR burst, PRE, and REF event scheduled. ACT is implicitly covered by RD/WR since burst will always issue and complete after a required ACT. The parameter is decremented when the event is serviced (completed). The controller will automatically transition to ACT power down, PRE power down, or SREF. Transition to ACT power down state scheduled from: 1) The RespondEvent, where read data is received from the memory. ACT power-down entry will be scheduled when one or more banks is open, all commands for the rank have completed (no more commands scheduled), and there are no commands in queue for the rank Transition to PRE power down scheduled from: 1) respondEvent, when all banks are closed, all commands have completed, and there are no commands in queue for the rank 2) prechargeEvent when all banks are closed, all commands have completed, and there are no commands in queue for the rank 3) refreshEvent, after the refresh is complete when the previous state was ACT power-down 4) refreshEvent, after the refresh is complete when the previous state was PRE power-down and there are commands in the queue. Transition to SREF will be scheduled from: 1) refreshEvent, after the refresh is completes when the previous state was PRE power-down with no commands in queue Power-down exit commands are scheduled from: 1) The refreshEvent, prior to issuing a refresh 2) doDRAMAccess, to wake-up the rank for RD/WR command issue. Self-refresh exit commands are scheduled from: 1) The next request event, when the queue has commands for the rank in the readQueue or there are commands for the rank in the writeQueue and the bus state is WRITE. Change-Id: I6103f660776e36c686655e71d92ec7b5b752050a Reviewed-by: Radhika Jagtap <radhika.jagtap@arm.com>
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