From 7bd68dbc368e2d877f6159f5d0039198983e459a Mon Sep 17 00:00:00 2001 From: Jose Marinho Date: Thu, 19 Oct 2017 18:45:26 +0100 Subject: [PATCH] cpu: Make automatic transition to OFF optional Add the power_gating_on_idle option to control whether a core automatically enters the power gated state. The default behaviour is to transition to clock gated when idle, but not to power gated. When this option is set to true, the core automatically transitions to the power gated state after a configurable latency. Change-Id: Ida98c7fc532de4140d0e511c25613769b47b3702 Reviewed-on: https://gem5-review.googlesource.com/5741 Reviewed-by: Jason Lowe-Power Maintainer: Andreas Sandberg --- src/cpu/BaseCPU.py | 4 ++++ src/cpu/base.cc | 12 +++++++++--- src/cpu/base.hh | 5 ++++- 3 files changed, 17 insertions(+), 4 deletions(-) diff --git a/src/cpu/BaseCPU.py b/src/cpu/BaseCPU.py index 0e131ae0a..1bf2c1e35 100644 --- a/src/cpu/BaseCPU.py +++ b/src/cpu/BaseCPU.py @@ -138,6 +138,10 @@ class BaseCPU(MemObject): pwr_gating_latency = Param.Cycles(300, "Latency to enter power gating state when all contexts are suspended") + power_gating_on_idle = Param.Bool(False, "Control whether the core goes "\ + "to the OFF power state after all thread are disabled for "\ + "pwr_gating_latency cycles") + function_trace = Param.Bool(False, "Enable function trace") function_trace_start = Param.Tick(0, "Tick to start function trace") diff --git a/src/cpu/base.cc b/src/cpu/base.cc index 78cf4196c..af55ee1d6 100644 --- a/src/cpu/base.cc +++ b/src/cpu/base.cc @@ -138,6 +138,7 @@ BaseCPU::BaseCPU(Params *p, bool is_checker) addressMonitor(p->numThreads), syscallRetryLatency(p->syscallRetryLatency), pwrGatingLatency(p->pwr_gating_latency), + powerGatingOnIdle(p->power_gating_on_idle), enterPwrGatingEvent([this]{ enterPwrGating(); }, name()) { // if Python did not provide a valid ID, do it here @@ -493,7 +494,8 @@ BaseCPU::schedulePowerGatingEvent() return; } - if (ClockedObject::pwrState() == Enums::PwrState::CLK_GATED) { + if (ClockedObject::pwrState() == Enums::PwrState::CLK_GATED && + powerGatingOnIdle) { assert(!enterPwrGatingEvent.scheduled()); // Schedule a power gating event when clock gated for the specified // amount of time @@ -536,8 +538,12 @@ BaseCPU::suspendContext(ThreadID thread_num) // All CPU threads suspended, enter lower power state for the CPU ClockedObject::pwrState(Enums::PwrState::CLK_GATED); - //Schedule power gating event when clock gated for a configurable cycles - schedule(enterPwrGatingEvent, clockEdge(pwrGatingLatency)); + // If pwrGatingLatency is set to 0 then this mechanism is disabled + if (powerGatingOnIdle) { + // Schedule power gating event when clock gated for pwrGatingLatency + // cycles + schedule(enterPwrGatingEvent, clockEdge(pwrGatingLatency)); + } } void diff --git a/src/cpu/base.hh b/src/cpu/base.hh index 7039fcfbc..13c56a945 100644 --- a/src/cpu/base.hh +++ b/src/cpu/base.hh @@ -588,10 +588,13 @@ class BaseCPU : public MemObject bool waitForRemoteGDB() const; Cycles syscallRetryLatency; + // Enables CPU to enter power gating on a configurable cycle count protected: - const Cycles pwrGatingLatency; void enterPwrGating(); + + const Cycles pwrGatingLatency; + const bool powerGatingOnIdle; EventFunctionWrapper enterPwrGatingEvent; }; -- 2.30.2