Presentation on theme: "Processor Power Management Overview. Page 2 Agenda Introduction Overview of all power states Global States Device States CPU States PCIe Link."— Presentation transcript:
Processor Power Management Overview
Page 2 Agenda Introduction Overview of all power states Global States Device States CPU States PCIe Link PM States Sleep States AMT States
Page 3 Agenda
Page 4 Power Management under ACPI Advanced Configuration and Power Management Interface New concepts beyond APM − Fine granularity on CPU clock control − Multiple system sleeping states − Individual device management without H/W traps and timers − Thermal Management Primary methodology for current power management. Define Power States within the platform. –Lx States : Link States (for DMI and PEG) –Dx States : Device States –Cx States : CPU States. –Sx States : Sleep (System) States. –Mx States : ME (AMT)States. –Gx States : Global States.
Page 5 Agenda
Page 6 G0(Working State) - System is running - Power is on G2(Soft Off) - No System Traffic - System is off - Small part of ICH remains on to accept wake up event. G1(Sleeping State) No System Traffic MCH, ICH and CPU off G3(Mech. Off) System is unplugged RTC battery continues to supply power to RTC -Individual devices can be in Dx and processor can be in Cx G0/S0/C0: Full On G0/S0/C1: Auto Halt G0/S0/C2: Stop Grant G0/S0/C3: Stop Clock G0/S0/C4: Stop Clock with lower CPU voltage G0/S0/C5 : Stop Clock with partial power off G1/S1: Stop Grant G1/S3: Suspend to ram (STR) G1/S4: Suspend to Disk (STD) G2/S5: Soft Off G3 : no power at all ( no battery or the system is insufficient supply level to wake) Wake event PWR plug in & AFTERG3_EN=1 PWR plug in & AFTERG3_EN=0 Sleep / Hibernate OS initiate Power off Global system state
Page 7 Agenda
Page 8 Device States : General D0 Fully-On This state is assumed to be the highest level of power consumption. The device is completely active. D1 - D2 Optional. Expected to save more power and preserve less device context than D0. D2 save more power than D1 but the latency is high. D3 Off - Power has been fully removed from the device. The device context is lost when this state is entered, so the OS software will reinitialize.
Page 9 Agenda
Page 10 CPU States : General C0 Processor Power State –Normal state. While the processor is in this state, it executes instructions. C1-C5 Processor Power State –Non executing power state. –The deeper the C state, the lower the power consumed by the processor in that state. Processor power in C1 is higher than the processor power in C4. –The deeper the C state, the higher the entry and exit latency of that state Entry/exit latency of C4 is higher than that of C1
Page 11 Intel CPU States StateEntry MethodBus Masters Allowed NotesBreak Event C0--Allo CPU is executing instructions C1AutoHalt inst.Allo Entered by CPU when it has nothing to do o Transparent to chipset Interrupt events (SMI, SCI..) C2Level 2 I/O read (LvL2) Allo ICH asserts STPCLK# o MCH may dynamically assert SLP# o Most CPU I/F signals are latched Interrupt (Key stroke, Mouse Movement, RTC) C3Level 3 I/O read (LvL3) only isoc*o ICH asserts STPCLK#, DPSLP#, STP_CPU# o MCH or ICH asserts SLP# o Most CPU I/F signals are latched o Bus master snoop request o Unmasked interrupt: SMI#, NMI# o CPU break (FERR#) C4Level 4 I/O read (LvL4) or C4onC3 only isoc*o ICH asserts STPCLK#, DPSLP#, STP_CPU#, DPRSTP#, DPRSLPVR o MCH or ICH asserts SLP# o Most CPU I/F signals are latched o Bus master snoop request o Unmasked interrupt: SMI#, NMI# o CPU break (FERR#)
Page 12 Intel CPU States StateEntry Method Bus Masters Allowed NotesBreak C5/C6Level 5/6 I/O read (LvL5/LvL6) Allo CPU flushes cache prior to entry, so snoops aren’t necessary. CPU will be [almost] fully powered down. o ICH asserts STPCLK#, DPSLP#, STP_CPU#, DPRSTP#, DPRSLPVR, #PMSYNC o MCH or ICH asserts SLP# o Most CPU I/F signals are latched o Same pins as C4, but different timings and abbreviated messaging Interrupt events
Page 13 Intel® Deep Power Down Technology (C6) Flexible C-States to Select Idle Power Level vs. Responsiveness
Page 14 C2 Entry/Exit Sequences Note: “M-I link” is DMI. “SG” message on “M-I link” should be “Req-C2”
Page 15 C3 Entry Sequences
Page 16 C3 Exit Sequences
Page 17 C4 Entry Sequences
Page 18 C4 Exit Sequences
Page 19 C5/C6 Entry Sequences
Page 20 C5/C6 Exit Sequences
Page 21 NHM CPU States NHM supports C0, C1, C1E, C3, C6 and C7. C7 is identical to C6 at core level but different Uncore power optimization. C7 is an overall package state where all cores have lost their registers, last level cache is at its minimum voltage but uncore is still in retention voltage On NHM, STPCLK#, SLP# and DPSLP# signals are removed due to platform change and CSI bus interface. Not all package C-state will be supported on all versions of NHM like Uncore power reduction features on C3 and lower power states maybe fused off in desktop or server parts.
Page 22 Agenda
Page 23 Link PM States L0 – Active state TLP(Transaction Layer Packet)’s and DLLP(Data Link Layer Packet)’s are permitted L0s – Low resume latency, energy saving “standby” state: no TLP/DLLP during L0s state quick entry/exit, exit in the order of 100 ns for Intel chipset L0s is single-directional. A transmitter can initiate L0s without the other port initiating L0s. Main power and clocks remain. Chipset gates some internal logic. L1 – lower power standby state – Higher latency PM state: Downstream port initiates when the device power state is programmed to non D0 state(D3) no TLP/DLLP during L1 state. Main power and clocks remain. Exit in order of micro seconds.
Page 24 Link PM States (Contd..) L2/3 ready – Staging point for L2/L3 – Required for PCIe PM before entering L2 or L3 state, this is not a real link state, it is just a phase requiring protocol handshake before entering L2 or L3. A device must be in D3 state before entering L2/3 ready System will place link L2/3 ready state before entering S3/S4/S5. L2 – Auxiliary powered Link deep energy state. L2 is optionally supported. Main power and clks are removed the device has aux power to perform link reactivation through beacon, WAKE#, PME context and detection logic. L3 – Link off state. Zero power state.
Page 25 Link PM States (Contd..) Summary of Link PM States: L-State Description Used By SW Directed PM Used By ASPM L0Fully ActiveYes(D0) L0sStandbyNoYes(D0) L1Lower Power Standby Yes(D1-D3hot)Yes(D0) L23 Ready Staging point for power removal Yes (links to PME_turn_off message ) No L2Low Power Sleep State YesNo L3Off (No Vaux)N/ANo LdnTransitional State before L0 YesNo
Page 26 Link PM States (Contd..) ASPM Control: Allows Hardware controlled PCIe dynamic link power reduction. ValueDescription 00 – DisabledPort must not bring a Link into L0s state. Port must not initiate a PM_active_State_Request_L1 DLLP to other end of the link Port receiving a L1 request from other agent must respond with negative acknowledgement. 01b – L0s Entry Enabled Port must bring a Link into L0s state when all conditions are met. Port must not initiate a PM_active_State_Request_L1 DLLP to other end of the link Port receiving a L1 request from other agent must respond with negative acknowledgement. 10b – L1 Entry Enabled Port’s transmitter must not bring a Link into L0s state. Port may issue a PM_active_State_Request_L1 DLLP to other end of the link Port receiving a L1 request from other agent must respond with positive acknowledgement.
Page 27 Link PM States (Contd..) ASPM Control: ValueDescription 11b – L0s and L1 Entry Enabled Port’s transmitter must bring a Link into L0s state. Port may issue a PM_active_State_Request_L1 DLLP to other end of the link Port receiving a L1 request from other agent must respond with positive acknowledgement.
Page 28 Link PM States (Contd..) Relationship between Link and Device PM State. Device State Permissible Interconnect Link State D0L0, L0s, L1 (ASPM) D1L1 D2L2 D3hotL1, L2/L3 ready D3coldL2, L3
Page 29 System and DMI Link Power States System States CPU State DescriptionLink State SW Controlled S0C0Fully Operation. Opportunistic Link Active State L0/L0 s/L1 N/A S0C1CPU Auto HaltL0/L0 s/L1 Yes S0C2CPU Stop ClockL0/L0 s/L1 Yes S0C3Deep Sleep: CPU’s clock halted via STP_CPU# assertion. MCH and ICH still being clocked L0/L0 s/L1 Yes
Page 30 System and DMI Link Power States System States CPU State DescriptionLink State SW Controlled S0C4Deeper Sleep: CPU’s clock halted via STP_CPU# assertion and CPU’s voltage lowered. L0/L0 s/L1 Yes S1/S1DC2S1D same as C2L0/L0 s/L1 Yes S3/S4/ S5 N/ASTR/STD/OffL3Yes
Page 31 Agenda
Page 32 Sleep States – User Point of View StateCommon NamesDescription S1Stand By, Powered on Suspend (refers to S1M state – last supported on ICH5) Entered by pressing sleep button, closing lid, system idle, etc. System appears mostly off (LED’s may indicate Stand By). Common wake events include power button, sleep button, mouse movement, modem ring, etc. System wakes quickly and all programs are still running. S2Not supported by Intel chipsets S3Stand By, Suspend to RAM To user, appears the same as S1, but in mobile system the battery can maintain S3 much longer. Wake will take longer than S1, but still very fast. S3 is “suspend” when pressing Fn + F4. S4Hibernate, Suspend to Disk Entered by user direction or system idle. System appears off. Most common wake event would be power button, but all others are still possible. System takes longer to wake than S3, but all programs are still running. S4 is “hibernate” when pressing Fn + F12. S5Shut Down, Soft Off Entered by user direction (Start -> Shut Down). Very similar to S4, but a full boot occurs on wake (no programs remain running from previous S0). Desktop must stay plugged in, laptop must have charged battery, otherwise platform is in G3.