阅读说明：本技术 针对基于外围组件互连快速（pcie）的设备的系统功率管理 (System power management for Peripheral Component Interconnect Express (PCIE) -based devices ) 是由 D·V·穆拉利 M·克里希纳 T·塞尔万姆 S·迪亚斯 T·张 于 2020-05-14 设计创作，主要内容包括：用于针对外围组件互连快速(PCIE)设备的功率管理的系统和方法,允许PCIE终端在PCIE链路空闲时进入高级低功率状态。这些高级低功率状态可以包括：通过完全关闭在PCIE终端内的功率轨和时钟来放大时钟频率。此外,使用唤醒信号(比如时钟请求(CLKREQ或CLKREQ#)信号)可以允许终端相对快速地醒来并且恢复操作,以便避免用户体验的降级或数据的丢失。(Systems and methods for power management for Peripheral Component Interconnect Express (PCIE) devices allow PCIE terminals to enter an advanced low power state when PCIE links are idle. These advanced low power states may include: the clock frequency is amplified by completely turning off the power rails and clocks within the PCIE terminal. Furthermore, the use of a wake-up signal, such as a clock request (CLKREQ or CLKREQ #) signal, may allow the terminal to wake-up and resume operation relatively quickly in order to avoid degradation of the user experience or loss of data.)

1. A method for reducing power consumption for a Peripheral Component Interconnect Express (PCIE) terminal, comprising:

starting a timer after entering the low power state; and

entering at least a partial system power collapse at the PCIE terminal when the timer expires without being active on an associated PCIE link.

2. The method of claim 1, further comprising:

registering a signal with wake-up capability before entering at least the partial system power collapse.

3. The method of claim 2, wherein registering the wake-up capable signal comprises: the CLKREQ # signal is registered as an interrupt with wake-up capability.

4. The method of claim 1, further comprising:

removing the vote for PCIE resources after the timer expires and before entering at least the partial system power collapse.

5. The method of claim 1, wherein the low power state comprises an L1 substate (L1 ss).

6. The method of claim 1, wherein entering at least the partial system power collapse comprises: and at least closing the clock in the PCIE terminal.

7. The method of claim 1, wherein entering at least the partial system power collapse comprises: reducing power at least from the power domain.

8. The method of claim 7, wherein reducing power from at least the power domain comprises: at least the voltage rails are turned off.

9. The method of claim 7, wherein reducing power from at least the power domain comprises: scaling down output from at least the power domain.

10. The method of claim 1, further comprising: receiving a wake-up signal after at least entering the partial system power collapse.

11. The method of claim 10, wherein receiving the wake-up signal comprises: the CLKREQ # signal is received.

12. The method of claim 10, further comprising: waking up from at least the partial system power collapse after receiving the wake-up signal.

13. The method of claim 1, wherein entering at least the partial system power collapse comprises: entering a full system power collapse without notifying another PCIE terminal associated with the PCIE link.

14. The method of claim 1, further comprising: receiving a link inactivity timeout interrupt signal after the timer expires.

15. The method of claim 1, further comprising: reducing the clock frequency before entering at least said partial system power collapse.

16. A device comprising a root complex, the root complex comprising:

a Peripheral Component Interconnect Express (PCIE) interface configured to couple to a PCIE link;

a timer; and

a control circuit configured to:

starting the timer after entering a low power state; and

entering at least a partial system power collapse when the timer expires without activity on the PCIE link.

17. The device of claim 16, wherein the control circuitry is further configured to: registering a signal with wake-up capability before entering at least the partial system power collapse.

18. The device of claim 16, wherein the control circuitry is further configured to: removing the vote for PCIE resources after the timer expires and before entering at least the partial system power collapse.

19. The device of claim 16, further comprising a clock, and wherein the control circuitry is further configured to: shutting down the clock upon at least entering the partial system power collapse.

20. The device of claim 16, wherein entering at least the partial system power collapse comprises: reducing power at least from the power domain.

21. The device of claim 16, wherein the control circuitry is further configured to: receiving a wake-up signal after at least entering the partial system power collapse.

22. The apparatus of claim 16, integrated into a device selected from the group consisting of: a set top box, an entertainment unit, a navigation device, a communications device, a fixed location data unit, a mobile location data unit, a Global Positioning System (GPS) device, a mobile phone, a cellular phone, a smart phone, a Session Initiation Protocol (SIP) phone, a tablet device, a tablet phone, a server, a computer, a portable computer, a mobile computing device, a wearable computing device, a desktop computer, a Personal Digital Assistant (PDA), a monitor, a computer display, a television, a tuner, a radio, a satellite radio, a music player, a digital music player, a portable music player, a digital video player, a Digital Video Disc (DVD) player, a portable digital video player, an automobile, a vehicle component, an avionics system, a drone, and a multi-axis helicopter.

23. A device comprising an endpoint, the endpoint comprising:

a Peripheral Component Interconnect Express (PCIE) interface configured to couple to a PCIE link;

a timer; and

a control circuit configured to:

starting the timer after entering a low power state; and

entering at least a partial system power collapse when the timer expires without activity on the PCIE link.

24. The device of claim 23, wherein the control circuitry is further configured to: registering a signal with wake-up capability before entering at least the partial system power collapse.

25. The device of claim 23, wherein the control circuitry is further configured to: removing the vote for PCIE resources after the timer expires and before entering at least the partial system power collapse.

26. The device of claim 23, further comprising a clock, and wherein the control circuitry is further configured to: shutting down the clock upon at least entering the partial system power collapse.

27. The device of claim 23, wherein entering at least the partial system power collapse comprises: reducing power at least from the power domain.

28. The device of claim 23, wherein the control circuitry is further configured to: receiving a wake-up signal after at least entering the partial system power collapse.

29. The apparatus of claim 23, integrated into a device selected from the group consisting of: a set top box, an entertainment unit, a navigation device, a communications device, a fixed location data unit, a mobile location data unit, a Global Positioning System (GPS) device, a mobile phone, a cellular phone, a smart phone, a Session Initiation Protocol (SIP) phone, a tablet device, a tablet phone, a server, a computer, a portable computer, a mobile computing device, a wearable computing device, a desktop computer, a Personal Digital Assistant (PDA), a monitor, a computer display, a television, a tuner, a radio, a satellite radio, a music player, a digital music player, a portable music player, a digital video player, a Digital Video Disc (DVD) player, a portable digital video player, an automobile, a vehicle component, an avionics system, a drone, and a multi-axis helicopter.

Technical Field

The technology of the present disclosure relates generally to Peripheral Component Interconnect Express (PCIE) links, and more particularly, to controlling power states for terminals associated with PCIE links.

Background

Computing devices have become commonplace in modern society. The popularity of computing devices is driven in part by the increased functionality and capabilities of computing devices. The diversified functionality and increased power is provided by the processing unit's ability to communicate with different peripheral devices. These peripheral devices, such as wireless modems or graphics cards, may be internal to the computing device, or peripheral devices, such as displays, sensors, etc., may be external to the computing device. To implement such myriad functions, various communication protocols and standards that allow Integrated Circuits (ICs) to communicate with each other have been gradually developed. One popular communication standard is the Peripheral Component Interconnect (PCI) standard, which has a variety of permutations. One of the most popular permutations of the PCI standard is the PCI express (PCIE) standard. At the same time, there is still pressure to reduce power consumption in computing devices.

Disclosure of Invention

Aspects disclosed in the detailed description include systems and methods for power management for Peripheral Component Interconnect Express (PCIE) -based devices. In particular, exemplary aspects of the present disclosure allow PCIE terminals to enter an advanced low power state when PCIE links are idle. These advanced low power states may include: the clock frequency is amplified by completely turning off the power rails and clocks within the PCIE terminal. Furthermore, the use of a wake-up signal, such as a clock request (CLKREQ or CLKREQ #) signal, may allow PCIE terminals to wake up and resume operation relatively quickly in order to avoid degradation of the user experience or loss of data.

In this regard, in one aspect, a method for reducing power consumption of a PCIE terminal is disclosed. The method comprises the following steps: after entering the low power state, a timer is started. The method further comprises the following steps: when a timer expires without activity on the associated PCIE link, at least a partial system power collapse is entered at the PCIE terminal.

In another aspect, a device comprising a root complex is disclosed. The root complex includes a PCIE interface configured to be coupled to a PCIE link. The root complex also includes a timer. The root complex also includes control circuitry. The control circuit is configured to: after entering the low power state, a timer is started. The control circuit is further configured to: when the timer expires without activity on the PCIE link, at least a partial system power collapse is entered.

In another aspect, a device comprising an endpoint is disclosed. The endpoint includes a PCIE interface configured to couple to a PCIE link. The endpoint also includes a timer. The endpoint also includes a control circuit. The control circuit is configured to: after entering the low power state, a timer is started. The control circuit is configured to: when the timer expires without activity on the PCIE link, at least a partial system power collapse is entered.

Drawings

Fig. 1A is a block diagram of an exemplary computing device that may include a Peripheral Component Interconnect Express (PCIE) link having an asymmetric power state;

fig. 1B is a block diagram of an exemplary computing system with devices coupled by PCIE links;

fig. 2 shows a block diagram of an exemplary PCIE endpoint device, and in particular configuration registers within the PCIE endpoint device;

fig. 3 illustrates a block diagram of a host having a processor and PCIE hardware having registers, according to an exemplary aspect of the present disclosure;

figure 4 is a sequence diagram of steps associated with placing PCIE terminals (and PCIE endpoints in particular) into an advanced low power state, in accordance with an exemplary aspect of the present disclosure;

fig. 5 is a sequence diagram of steps associated with placing PCIE terminals (and PCIE hosts in particular) into an advanced low power state, according to an exemplary aspect of the present disclosure.

Detailed Description

Some exemplary aspects of the present disclosure are now described with reference to the drawings. The word "exemplary" is used herein to mean "serving as an example, instance, or illustration. Any aspect described herein as "exemplary" is not necessarily to be construed as preferred or advantageous over other aspects.

Aspects disclosed in the detailed description include systems and methods for power management for Peripheral Component Interconnect Express (PCIE) -based devices. In particular, exemplary aspects of the present disclosure allow PCIE terminals to enter an advanced low power state when PCIE links are idle. These advanced low power states may include: the clock frequency is amplified by completely turning off the power rails and clocks within the PCIE terminal. Furthermore, the use of a wake-up signal, such as a clock request (CLKREQ or CLKREQ #) signal, may allow PCIE terminals to wake up and resume operation relatively quickly in order to avoid degradation of the user experience or loss of data.

Before addressing the details of how PCIE terminals are placed in advanced low power states, a brief overview of a PCIE architecture is provided with reference to fig. 1A-3. A discussion of the sequence by which a PCIE terminal is placed into an advanced low power state begins below with reference to fig. 4.

In this regard, fig. 1A illustrates an example of a computing device (i.e., a processor-based system 100) that may employ PCIE terminals capable of operating in an asymmetric power state or mode, according to an exemplary aspect of the present disclosure. In this example, the processor-based system 100 includes one or more Central Processing Units (CPUs) 102, each CPU including one or more processors 104. The CPU 102 may have a cache memory 106 coupled to the processor 104 for fast access to temporarily stored data. The CPU 102 is coupled to a system bus 108 and may be inter-coupled with master and slave devices included in the processor-based system 100. As is well known, the CPU 102 communicates with these other devices by exchanging address, control, and data information over the system bus 108. For example, the CPU 102 may communicate a bus transaction request to one or more memory controllers 110. Although not shown in fig. 1, a plurality of system buses 108 may be provided.

Other devices may be connected to the system bus 108. As shown in fig. 1A, these devices may include (but are not necessarily limited to) a memory controller 110, one or more PCIE controllers 112, one or more network interface controllers 114, and one or more display controllers 116, for example. Memory controller 110 may be coupled to one or more memory units 118. A PCIE controller 112 may be coupled to one or more PCIE devices 120 through one or more PCIE links 122. The network interface controller network 114 may be coupled to one or more network devices 124. Network device 124 may be any device configured to allow the exchange of data to and from network 126. Network 126 may be any type of network including, but not limited to, a wired or wireless network, a private or public network, a Local Area Network (LAN), a Wireless Local Area Network (WLAN), a Wide Area Network (WAN), a bluetooth network, and the internet. The network interface device 124 may be configured to support any type of communication protocol desired. In an exemplary aspect, the network interface device 124 may be a Mobile Data Modem (MDM) or other network device that allows the processor-based system 100 to communicate over one or more devices in a distributed or peer-to-peer manner through a defined network protocol. Note also that CPU 102 may communicate with peripheral devices over such a distributed network.

The CPU 102 may also be configured to access the display controller 116 over the system bus 108 to control information sent to one or more displays 128. The display controller 116 sends information to the display 128 to be displayed via one or more video processors (not shown) that process the information to be displayed into a format suitable for the display 128. Display 128 may include any type of display including, but not limited to, a Liquid Crystal Display (LCD), a plasma display, a Light Emitting Diode (LED) display, and the like.

In addition to system bus 108, there may be a power control block 130, power control block 130 coupling power to the various elements of processor-based system 100 through power links 132(1) - (N). The power control block 130 determines the overall system power based on votes from other subsystems or elements in the device. Although not shown, there may be one or more clocks that provide clock signals to the various elements of the processor-based system 100. Some clocks may be internal to a particular element, while others may be provided by an external reference clock.

Fig. 1B illustrates PCIE link 122 of processor-based system 100 with host 134, which host 134 may be an application processor, a system on a chip (SoC), or the like. Host 134 includes PCIE controller 112. The PCIE controller 112 is directly coupled to the plurality of devices 120(1) - (120N) and is coupled to a second plurality of devices 136(1) - (136 (M) through the switch 140. The PCIE controller 112 may be a PCIE Root Complex (RC) configured to be coupled to a plurality of PCIE links 122(1) -122(N + 1). Switch 140 communicates with devices 136(1) -136(M) via PCIE links 138(1) -138 (M). Devices 120(1) -120(N) and 136(1) -136(M) may be or may include PCIE endpoints.

In an exemplary aspect, the PCIE links 122(1) -122(N +1) and 138(1) -138(M) of fig. 1B may be in a single computing device, such as a computer, where the host 134 is a Central Processing Unit (CPU) and the devices 120(1) -120(N) and 136(1) -136(M) are internal components, such as hard disk drives, and the like. In a second exemplary aspect, PCIE links 122(1) -122(N +1) and 138(1) -138(M) of fig. 1B may be in a computing device, where host 134 is an Integrated Circuit (IC) on board, and devices 120(1) -120(N) and 136(1) -136(M) are other ICs within the computing device. In a third exemplary aspect, the PCIE links 122(1) -122(N +1) and 138(1) -138(M) of fig. 1B may be in a computing device having an internal host 134, the internal host 134 being coupled to external devices 120(1) -120(N) and 136(1) -136(M), such as servers coupled to one or more external storage drives. It should be appreciated that these aspects are not necessarily mutually exclusive, as different ones of these devices may be ICs, internal or external with respect to a single host 134.

FIG. 2 provides a block diagram of an apparatus 200 that may be one of apparatuses 120(1) -120(N) or apparatuses 136(1) -136 (M). In particular, device 200 acts as an endpoint in a PCIE system and may be, for example, a memory device including a memory element 202 and control circuitry 204 or an MDM including transceiver (Tx/Rx) circuitry configured to couple to an antenna (not shown) for wireless communication. The control circuit 204 may include an "always on" (represented as AO in fig. 2) circuit 205. Alternatively, the always-on circuit 205 may be in communication with the control circuit 204. Further, the device 200 includes PCIE hardware (also denoted as HW in fig. 2) elements 206, the PCIE hardware elements 206 including links or bus interfaces (sometimes referred to as PCIE link interfaces or PCIE only interfaces) configured to couple to PCIE links. PCIE hardware elements 206 may include a physical layer (PHY)208, physical layer (PHY)208 being a link or bus interface, or working in conjunction with a link or bus interface to communicate over a PCIE link. Control circuitry 204 communicates with PCIE hardware elements 206 over a system bus 210. PCIE hardware element 206 may also include a plurality of registers 212. The register 212 may be conceptually divided into a configuration register 214 and a capability register 216. The configuration registers 214 and the capability registers 216 are defined by the original PCI standard and the newer device, including the registers 214 and 216, is backward compatible with legacy devices. The PCIE standard further defines additional registers found in the PCIE extended configuration register space 218. These registers are not present in the original PCI standard and, therefore, PCI legacy devices typically do not address these additional registers. Although not explicitly shown, there may be a timer within the control circuitry 204 or in the PCIE hardware element 206 for exemplary aspects of the present disclosure.

Similarly, fig. 3 shows a host 300. Host 300 may include an application processor 302 (which may be CPU 102 of fig. 1A) or other processor core or control circuitry in communication with a memory element 304, memory element 304 having an operating system 306 operating therewith. Application processor 302 may include always-on circuitry 307 (denoted as AO in fig. 3). Alternatively, always-on circuit 307 may be in communication with application processor 302. A system bus 308 interconnects the application processor 302 with memory elements 304 and PCIE RCs (sometimes referred to as PCIE Hardware (HW)) 310. PCIE RC 310 may include PHY 312, PHY 312 being or operating with a link or bus interface configured to couple to (sometimes referred to as or only) a PCIE link interface. PCIE RC 310 also includes a plurality of registers. In particular, the PCIE RC 310 may include a STATUS register 314(CAM _ STATUS), a CONTROL register 316(CAM _ CONTROL), a configuration address register 318(CONFIG _ ADDR), and a DATA register 320(CONFIG _ DATA). Optionally, the plurality of registers may also include a lock register 322. These registers are defined by the PCIE standard and are not the focus of the present disclosure but are included for completeness. Again, although not explicitly shown, a timer may be present in the application processor 302, the PCIE RC 310, or between the device 200 and the PCIE RC 310, which is used for exemplary aspects of the present disclosure.

While the concepts of the present disclosure may be applied to other types of communication links, the exemplary aspects of the present disclosure are well suited for use with the PCIE link 122 of fig. 1A. In particular, aspects of the present disclosure allow a PCIE endpoint (e.g., root complex or endpoint) to enter an advanced low power state. That is, while the PCIE standard defines the link active state (L0) as the active state, L1 as the low power state, where L1.1 and L1.2 (the general link low power state) are low power sub-states, even in these low power sub-states, the power domains (e.g., power rails) and clocks within the PCIE terminal are still active and may generate leakage currents or otherwise consume power. Since such power consumption accelerates the need to recharge the battery or may increase the electricity charge, there is pressure to reduce power consumption. While the PCIE standard does consider the L2 or L3 low power states, entering the L2 or L3 states requires a significant amount of idle time and also requires wake up time on the order of milliseconds, which may negatively impact performance. Entering the L2 or L3 state also requires coordination with the link partner. That is, entering the L2 or L3 state is a coordinated effort that requires synchronization from the cooperation of the two link partners, so if one end cannot enter the L2 or L3 state, neither end can enter the L2 or L3 state. Further, not all devices enable the L2 or L3 states, and thus, the devices may not enter a power domain and clock off state. Thus, it is more likely that a device may spend time in a link low power state with an idle link. In such a scenario, the system (without the present disclosure) cannot enter the lowest possible power state because the link low power state maintains an active clock and power domain to prevent the device from entering a power collapse. Accordingly, exemplary aspects of the present disclosure allow PCIE terminals to enter an advanced low power state, where power consumption may be reduced, such as by reducing clock frequency or allowing power rails (e.g., power control block 130) and clocks to be scaled down or turned off. Note that these changes may be stepwise (incremental). Initially, the clock frequency may be reduced, then the power rail output scaled, and then the power rail turned off depending on how long the link remains idle. The exact order of the step-wise power reduction may vary as needed or desired. PCIE terminals also allow for fast wake-up (e.g., on the order of microseconds) upon receiving a wake-up signal, such as a clock request (variously referred to as CLKREQ or CLKREQ #, where # represents an active signal) signal at an always-on block within an IC.

Figure 4 provides a sequence diagram 400 that explains the entry and exit of the advanced system low power state, where at least the endpoint 200 enters such an advanced low power state ranging from different clock frequencies up to a full power collapse. In this regard, fig. 4 begins with a PCIE link 122 between a PCIE endpoint 200 and a PCIE host 300 (e.g., an end of a PCIE link) being active and in a link active (L0) state (block 402). The various capability registers have previously indicated to the PCIE host 300 that a low power state (such as L1ss) is available, and the terminal enables the link inactivity timeout interrupt by enabling the link inactivity timer (block 404). When there is PCIE link activity (line 406), the PCIE link 122 remains active and is in a link active state (block 408). Note that while in the active state, the PCIE link 122 may be governed by PCIE standards (and in particular Active State Power Management (ASPM) rules) that allow the PCIE link 122 to enter and exit low power states based on activity on the PCIE link 122. That is, the ASPM rule is followed.

Note that the PCIE specification requires: the endpoint ports of both the interconnected root complex and the link should support the CLKREQ # signal as a bi-directional open-drain signal for supporting the link low power state. According to the PCIE specification, when the CLKREQ # signal is asserted (assert), an exit from the link low power state will be initiated. Exemplary aspects of the present disclosure use this functionality as explained herein, but other signals may be used.

At some point, the PCIE link 122 becomes idle (line 410), and the CLKREQ # signal is deasserted (de-assert) by the endpoint 200 to allow a link low power state (e.g., L1 or L1ss) to be entered (block 412). As noted above, entering and exiting link low power states is defined by the PCIE standard (e.g., ASPM). A link inactivity timer at endpoint 200 is enabled, the link inactivity timer having a threshold equal to the link inactivity interval (vertical line 414). Note that it is possible to resume activity on the PCIE link 122 before the link inactivity timer expires, and the PCIE link 122 returns to activity (generally represented by dashed line 415). However, during the link low power state, other subsystems within endpoint 200 may be idle and power may partially collapse (e.g., CPU) (line 416), although typically the clock and power domains remain active. If the PCIE link 122 remains in the link low power state (without exit) for the period of the timer (i.e., the time represented by line 414), a link inactivity timeout occurs (line 418). The interrupt controller 420 (which may be in the endpoint 200) (or other interrupt controller subsystem) issues a link inactivity timeout interrupt to the endpoint 200 (line 422), and the endpoint 200 registers a wake-up signal (e.g., the CLKREQ # signal (or other signal (or event) that serves as a link activity notification mechanism) to an always-on block 424 (which may be the always-on circuit 205) to act as a wake-up capable interrupt or trigger (line 426).

Having registered endpoint 200(CLKREQ #) as being awake-capable, the PCIE subsystem within endpoint 200 removes the vote for the PCIE resource in power control block 130 (block 428). The voting may include removing the vote for the power domain and clock, and CLKREQ # may be selectively gated (gate) to the PCIE controller. This vote removal allows for a system-wide power collapse for at least endpoint 200 in which the power domain and clock are shut down (line 430), scaled down, or otherwise reduced (e.g., sufficient power for memory retention may be maintained). One way in which this may be reduced is by varying the clock frequency.

At some subsequent time, a CLKREQ # switch notification is detected within the host 300 and treated as a request from one of the link partners to exit the link low power state (line 432). The endpoint 200 wakes up and exits power collapse such that the endpoint 200 comes out of power collapse (line 434). After exiting the power collapse, always on block 424 sends a CLKREQ # (or other wake-up signal) switch notification to PCIE host 300 (line 436). The host 300 then votes for PCIE resources (e.g., voltage rails and clocks) and de-registers the CLKREQ # interrupt (or other wake-up signal) (block 438). In addition, the host 300 votes for PCIE resources and ungated CLKREQ # to the PCIE controller (if this is enabled at block 428). The PCIE terminal exits the link low power state and the PCIE link 122 transitions to a link active state (e.g., L0) with allowed ASPMs (block 440), where PCIE link activity continues (line 442), allowing normal entry and exit into and out of the active and low power states. Note that entering and exiting the advanced low power state may occur automatically without coordination with other terminals. Note that the threshold for the timer may be set based on expected activity or use cases on the PCIE link 122.

Figure 5 provides a sequence diagram 500 illustrating entry and exit of an advanced system low power state in which at least host 300 enters such an advanced low power state ranging from a different clock frequency to a full power collapse. In this regard, fig. 5 begins with a PCIE link 122 between a PCIE endpoint 200 and a PCIE host 300 (e.g., an end of a PCIE link) being active and in a link active (L0) state (block 502). Various capability registers have previously indicated to PCIE host 300 that a low power state (such as L1ss) is available, and endpoint 200 initiates a link inactivity timeout interrupt by enabling a link inactivity timer (block 504). When there is PCIE link activity (line 506), the PCIE link 122 remains active and is in a link active state (block 508). Note that while in the active state, the PCIE link 122 may be governed by PCIE standards (and in particular ASPM rules) that allow the PCIE link 122 to enter and exit a low power state based on activity on the PCIE link 122. That is, the ASPM rule is followed.

At some point, the PCIE link 122 becomes idle (line 510) and the host 300 deasserts the CLKREQ # signal to allow a link low power state (e.g., L1 or L1ss) to be entered (block 512). As noted above, entering and exiting link low power states is defined by the PCIE standard (e.g., ASPM). A link inactivity timer at host 300 is enabled, the link inactivity timer having a threshold equal to the link inactivity interval (vertical line 514). Note that it is possible to resume activity on the PCIE link 122 before the link inactivity timer expires, and the PCIE link 122 returns to activity (generally represented by dashed line 515). However, during the link low power state, other subsystems within host 300 may be idle and power may partially collapse (line 516), although typically the clock and power domains remain active. If the PCIE link 122 remains in the link low power state (without exit) for the period of the timer (i.e., the time represented by line 514), a link inactivity timeout occurs (line 518). The interrupt controller 520 (or other interrupt controller subsystem) which may be in the host 300 issues a link inactivity timeout interrupt to the endpoint 200 (line 522), and the endpoint 200 registers with an always-on block 524 (which may be the always-on circuit 307) for a wake-up signal (e.g., the CLKREQ # signal (or other signal (or event) that serves as a link activity notification mechanism) to act as a wake-up capable interrupt or trigger (line 526).

Having registered the host 300(CLKREQ #) as being awake-able, the PCIE subsystem within the endpoint 200 removes the vote for the PCIE resource in the power control block 130 (block 528). The voting may include: votes for the power domain and clock are removed and CLKREQ # may be selectively gated to the PCIE controller. This vote removal allows for a full system power collapse for at least host 300 in which the power domain and clock are shut down, scaled down, or otherwise reduced (e.g., sufficient power for memory retention may be maintained) (line 530). One way in which this may be reduced is by varying the clock frequency.

At some subsequent time, a CLKREQ # switch notification is detected within the host 300 and treated as a request from one of the link partners to exit the link low power state (line 532). The host 300 wakes up and exits the power collapse such that the host 300 comes out of the power collapse (line 534). After exiting the power collapse, always-on block 524 sends a CLKREQ # (or other wake-up signal) switch notification to endpoint 200 (line 536). The host 300 then votes for PCIE resources (e.g., voltage rails and clocks) and de-registers the CLKREQ # interrupt (or other wake-up signal) (block 538). In addition, the host 300 votes for PCIE resources and de-gates CLKREQ # to the PCIE controller (if this is enabled at block 528). The PCIE terminal exits the link low power state and the link goes to the link active state (e.g., L0) with allowed ASPMs (block 540), where PCIE link activity continues (line 542), allowing normal entry and exit into and out of the active and low power states. Note that entering and exiting the advanced low power state may occur automatically without coordination with other terminals. Note that the threshold for the timer may be set based on expected activity or use cases on the PCIE link 122.

Systems and methods for power management for PCIE-based devices according to aspects disclosed herein may be provided in or integrated into any processor-based device. Examples include, but are not limited to, a set top box, an entertainment unit, a navigation device, a communication device, a fixed location data unit, a mobile location data unit, a Global Positioning System (GPS) device, a mobile phone, a cellular phone, a smart phone, a Session Initiation Protocol (SIP) phone, a tablet device, a tablet phone, a server, a computer, a portable computer, a mobile computing device, a wearable computing device (e.g., a smart watch, a health or fitness tracker, glasses, etc.), a desktop computer, a Personal Digital Assistant (PDA), a monitor, a computer display, a television, a tuner, a radio, a satellite radio, a music player, a digital music player, a portable music player, a digital video player, a Digital Video Disc (DVD) player, a portable digital video player, a video disc player, a portable media player, a portable media player, a portable, Automobiles, vehicle components, avionics systems, unmanned aerial vehicles, and multi-axis helicopters.

Those of skill would further appreciate that the various illustrative logical blocks, modules, circuits, and algorithms described in connection with the aspects disclosed herein may be implemented as electronic hardware, instructions stored in a memory or another computer-readable medium and executable by a processor or other processing device, or combinations of both. As an example, the apparatus described herein may be employed in any circuit, hardware component, IC, or IC chip. The memory disclosed herein may be any type and size of memory and may be configured to store any type of desired information. To clearly illustrate this interchangeability, various illustrative components, blocks, modules, circuits, and steps have been described above generally in terms of their functionality. How such functionality is implemented may depend on the particular application, design choice, and/or design constraints imposed on the overall system. Skilled artisans may implement the described functionality in varying ways for each particular application, but such implementation decisions should not be interpreted as causing a departure from the scope of the present disclosure.

The various illustrative logical blocks, modules, and circuits described in connection with the aspects disclosed herein may be implemented or performed with a processor, a Digital Signal Processor (DSP), an Application Specific Integrated Circuit (ASIC), an FPGA or other programmable logic device, discrete gate or transistor logic, discrete hardware components, or any combination thereof designed to perform the functions described herein. The processor may be a microprocessor, or in the alternative, the processor may be any conventional processor, controller, microcontroller, or state machine. A processor may also be implemented as a combination of computing devices (e.g., a combination of a DSP and a microprocessor, a plurality of microprocessors, one or more microprocessors in conjunction with a DSP core, or any other such configuration).

Aspects disclosed herein may be embodied in hardware and instructions stored in hardware, and may be located, for example, in Random Access Memory (RAM), flash memory, Read Only Memory (ROM), electronically programmable ROM (eprom), electrically erasable programmable ROM (eeprom), registers, hard disk, a removable hard disk, a CD-ROM, or any other form of computer-readable medium known in the art. An exemplary storage medium is coupled to the processor such the processor can read information from, and write information to, the storage medium. In the alternative, the storage medium may be integral to the processor. The processor and the storage medium may reside in an ASIC. The ASIC may be located in a remote station. In the alternative, the processor and the storage medium may reside as discrete components in a remote station, base station, or server.

It is also noted that the operational steps described in any of the exemplary aspects herein are described for the purpose of providing examples and discussion. The operations described may be performed in many different orders than that shown. Further, operations described in a single operational step may actually be performed in multiple different steps. Further, one or more of the operational steps discussed in the exemplary aspects may be combined. It is to be understood that the operational steps illustrated in the flowcharts may be subject to many different modifications as would be apparent to one of ordinary skill in the art. Those of skill in the art would further understand that information and signals may be represented using any of a variety of different technologies and techniques. For example, data, instructions, commands, information, signals, bits, symbols, and chips that may be referenced throughout the above description may be represented by voltages, currents, electromagnetic waves, magnetic fields or particles, optical fields or particles, or any combination thereof.

The previous description of the disclosure is provided to enable any person skilled in the art to make or use the disclosure. Various modifications to the disclosure will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other variations. Thus, the disclosure is not intended to be limited to the examples and designs described herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.