Patent Publication Number: US-10761582-B2

Title: Method and apparatus to optimize system battery-life for static and semi-static image viewing usage models

Description:
CROSS-REFERENCES TO RELATED APPLICATIONS 
     This Application claims the benefit of U.S. Provisional Patent Application No. 61/526,208, filed Aug. 22, 2011. This Applicant is related to U.S. patent application Ser. No. 13/251,195, filed on Sep. 30, 2011. 
    
    
     TECHNICAL FIELD 
     The present disclosure relates generally to the field of power management and more specifically to the field of power management in systems that use a graphics Processor. 
     BACKGROUND 
     Computer systems continue to evolve, with ever faster processing speeds, greater data handling capabilities, and increasing storage capacity. Computers have also been steadily reduced in size. This size reduction is most apparent in the laptop, notebook, tablet and hand-held computer markets. While desiring to continuously decrease the size and weight of laptops, notebooks, and hand-held computers, manufacturers have also steadily reduced the size and weight of on-board batteries. Because battery-life in laptops, notebooks, and hand-held computers is such a strong consideration, power management methods are utilized to increase battery-life. 
     Conventional computer systems can provide the user with a graphical user interface (GUI) that allows the user to define characteristics of system power management. In one exemplary embodiment, to save power in an idle mobile or notebook computer, a phased sleep process is provided after a detected period of inactivity. For example, the phased sleep process can begin by dimming a display device, such as a display panel, which reduces power consumption by turning down the backlight after the computer system has been idle for a prescribed length of time. A next phase can include turning the display panel off after a second prescribed length of time (e.g., display device in D 3 ). A further phase can put the computer system into a sleep state after a third prescribed length of time (e.g., suspend in S 3 ). Lastly, the computer system can be shut down in a hibernation step after a fourth prescribed length of time (e.g., hibernate in S 4 ). Each of these steps in a phased sleep process can save progressively more power with a primary difference between the steps being the amount of power and the latency to enter or exit the state. To undim or wake-up the display or turn the display back on, a user needs to interact with the computer system (e.g. move the mouse or make contact with a touch pad or keyboard). Such interaction with the computer system will result in the display panel exiting the current phase of the phased sleep process, from as simple a step as undimming the display panel to resuming from a sleep state. 
     While many activities carried out on a computer system can be performed without interference or disruption from such power conservation states, passive or semi-passive activities will often be interpreted as computer system inactivity, resulting in the undesirable steps such as dimming the backlight or disabling the display entirely. Such passive or semi-passive activities include for example, the reading of text found in eBook reader programs, word processing programs, reading web pages, and other modes of use wherein the computer user spends the majority of the time viewing the computer screen with minimal mouse, keyboard or other system interaction. Other user activities can also potentially result in the display device undesirably dimming or powering down while it was being used. While the display can be re-enabled, and backlight can be easily restored to the desired level, by the user merely moving the mouse, touching the keyboard, or interacting with another input device, it requires a continuing pattern of user interactions with the computer system. Requiring such distracting, repeated and annoying interactions can often result in user frustration, and the user selecting power management timer settings that are so long (before dimming or powering down the display panel) that they defeat the purpose of power management. For example, to prevent the annoyance of the display device from undesirable disabling while the user is verbally presenting content on the screen or occasionally reading email while in a meeting, the user may select a maximum length of time before display disabling takes place, or even worse, turn off power conservation entirely. This dramatically shortens the battery-life and results in user complaints on the inability to achieve the product&#39;s original stated battery-life. 
     SUMMARY OF THE INVENTION 
     Embodiments of the present invention provide solutions to the challenges inherent in power conservation through graphics processor and display device usage management. In one embodiment of the present invention, a computer system for managing entry into a power management state is disclosed. The computer system comprises: a graphics processor, a display controller comprising a display-local frame buffer, a display device, and a memory. The memory stores instructions, that when executed by the computer system, perform a method of entering a power management state. The method comprises detecting that the computer system is idle. With the computer system idle, the display-local frame buffer is activated. Display information transmitted by the graphics processor is stored in the display-local frame buffer. Initially a power reduction state is initiated for the graphics subsystem including the graphics processor, and the display device is placed in a self-refresh state with the display self-refreshing from information stored in the local frame buffer. 
     In another embodiment, after a further period of idleness the system is placed in a system-level suspend state while the display is kept in the self-refresh state. Exemplary embodiments provide visual continuity for the user during periods of uninterrupted passive viewing of the display device while conserving an equivalent amount of power as more intrusive conventional power management methods. Rather than the typical disruptive experience, exemplary embodiments replace conventional idle or sleep states with states that support self-refreshing the display panel while conserving power by disabling or powering down the graphics processor, or placing the larger system into suspend sleep or powered-down state. 
     In a further embodiment of the present invention, a computer system comprises a graphics processor, a display device, a local frame buffer, and a processor. The graphics processor generates display information for the display device. The graphics processor is also able to enter a power reduction state. The local frame buffer stores the display information from the graphics processor. The local frame buffer can also self-refresh the display device with the stored display information during a power reduction state of the graphics processor. The processor detects a system idle event, activates the local frame buffer and initiates the power reduction state of the graphics processor. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Embodiments of the present invention will be better understood from a reading of the following detailed description, taken in conjunction with the accompanying drawing figures in which like reference characters designate like elements and in which: 
         FIG. 1  illustrates an exemplary simplified block diagram of a computer controlled system having power management in accordance with an embodiment of the present invention; 
         FIG. 2  illustrates an exemplary simplified block diagram of a graphics processor and display device interface in accordance with an embodiment of the present invention; 
         FIG. 3  illustrates an exemplary simplified block diagram of another computer controlled system having power management in accordance with an embodiment of the present invention; 
         FIG. 4  illustrates an exemplary simplified block diagram of a computer controlled system having power management in accordance with an embodiment of the present invention for entering a power management state; 
         FIG. 5  illustrates an exemplary simplified block diagram of exiting a power management state in accordance with an embodiment of the present invention; 
         FIG. 6  illustrates an exemplary on-screen graphical user interface in accordance with an embodiment of the present invention; 
         FIG. 7  illustrates an exemplary flow diagram of a method of power management in accordance with an embodiment of the present invention; 
         FIG. 8  illustrates an exemplary flow diagram of a method of power management in accordance with an embodiment of the present invention; 
         FIG. 9  illustrates an exemplary simplified block diagram of a computer controlled system having power management in accordance with an embodiment of the present invention; and 
         FIG. 10  illustrates an exemplary flow diagram of a method of managing computer suspend states in accordance with an embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     Reference will now be made in detail to the preferred embodiments of the present invention, examples of which are illustrated in the accompanying drawings. While the invention will be described in conjunction with the preferred embodiments, it will be understood that they are not intended to limit the invention to these embodiments. On the contrary, the invention is intended to cover alternatives, modifications and equivalents, which may be included within the spirit and scope of the invention as defined by the appended claims. Furthermore, in the following detailed description of embodiments of the present invention, numerous specific details are set forth in order to provide a thorough understanding of the present invention. However, it will be recognized by one of ordinary skill in the art that the present invention may be practiced without these specific details. In other instances, well-known methods, procedures, components, and circuits have not been described in detail so as not to unnecessarily obscure aspects of the embodiments of the present invention. The drawings showing embodiments of the invention are semi-diagrammatic and not to scale and, particularly, some of the dimensions are for the clarity of presentation and are shown exaggerated in the drawing Figures. Similarly, although the views in the drawings for the ease of description generally show similar orientations, this depiction in the Figures is arbitrary for the most part. Generally, the invention can be operated in any orientation. 
     Notation and Nomenclature: 
     Some portions of the detailed descriptions, which follow, are presented in terms of procedures, steps, logic blocks, processing, and other symbolic representations of operations on data bits within a computer memory. These descriptions and representations are the means used by those skilled in the data processing arts to most effectively convey the substance of their work to others skilled in the art. A procedure, computer executed step, logic block, process, etc., is here, and generally, conceived to be a self-consistent sequence of steps or instructions leading to a desired result. The steps are those requiring physical manipulations of physical quantities. Usually, though not necessarily, these quantities take the form of electrical or magnetic signals capable of being stored, transferred, combined, compared, and otherwise manipulated in a computer system. It has proven convenient at times, principally for reasons of common usage, to refer to these signals as bits, values, elements, symbols, characters, terms, numbers, or the like. 
     It should be borne in mind, however, that all of these and similar terms are to be associated with the appropriate physical quantities and are merely convenient labels applied to these quantities. Unless specifically stated otherwise as apparent from the following discussions, it is appreciated that throughout the present invention, discussions utilizing terms such as “processing” or “accessing” or “executing” or “storing” or “rendering” or the like, refer to the action and processes of a computer system, or similar electronic computing device, that manipulates and transforms data represented as physical (electronic) quantities within the computer system&#39;s registers and memories and other computer readable media into other data similarly represented as physical quantities within the computer system memories or registers or other such information storage, transmission or display devices. When a component appears in several embodiments, the use of the same reference numeral signifies that the component is the same component as illustrated in the original embodiment. 
     Visual Continuity During Passive Viewing 
     Embodiments of the present invention provide solutions to the increasing challenges inherent in power management through graphics processor and display device usage management. Various exemplary embodiments of the present invention provide the user with “visual continuity” for periods of uninterrupted passive viewing of the display device while conserving power. As discussed in detail below, self-refresh modes are utilized in user-optioned power management states to allow a display device, after a detected period of inactivity, to be refreshed from a local frame buffer of a self-refresh controller, thereby allowing the GPU to be disabled or powered down, with the display device remaining undimmed. In an exemplary embodiment, a computer system can provide a user-specified preference for “visual continuity” that uses display panel self-refresh and GPU sleep modes, rather than the conventional display panel backlight dimming and display panel power-down energy conservation settings. Such preferences can be passed to the GPU drivers at initialization and are changeable at run-time. Self-refreshing the display panel while sleeping (or powering down) the GPU may be transparent to the user. 
     Display panel self-refresh is a technology where the display panel itself, or a controller module that drives the display panel, has the ability to self-refresh from a local frame buffer the current display information. Such a frame buffer can be local to the self-refresh controller. When connected to a self-refresh capable display panel, the GPU is not required to scan-out pixels (display information) for a constant, unchanging, display image. Thus, the GPU (including its display subsystems) can be put into a low-power sleep state or optimally shut-down until a new or altered image needs to be sent to the display panel. Such new or altered images can be the result of user interactions, such as turning a page, moving a mouse, or other actions with input devices. 
       FIG. 1  is an exemplary simplified block diagram of a computer controlled system comprising a graphics processing unit (GPU)  102 , a bridge  105  with a self-refresh controller (SRC)  106  and a display panel  110  with timer controller  112 . The GPU  102  and self-refresh controller  106  each comprise a local frame buffer  104 ,  108 . As illustrated in  FIG. 1 , an exemplary GPU  102 , bridge  105 , and display panel  110  can communicate using an embedded display port (eDP) standard which defines standardized display panel interfacing for internal connections (e.g., graphics cards to notebook display panels), or by using a low-voltage differential signaling (LVDS) standard for transmitting video data from graphics adapters to computer monitors, such as display panels in notebook computers. 
       FIG. 2  is another exemplary simplified block diagram of an electronic system comprising a graphics processing unit (GPU)  102  and display panel  210 . As illustrated in  FIG. 2 , the display panel  210  comprises an integrated self-refresh controller  106  connected with a timer controller  112 . As further illustrated in  FIG. 2 , the integrated self-refresh controller  106  is connected to an integrated SRC local frame buffer  108 , while the GPU  102  is similarly connected to a frame buffer  104 . As illustrated in  FIGS. 1 and 2 , the SRC  106  and SRC local frame buffer  106  may be located in a display panel  210 , or in a bridge  105  between the display panel  110  and the GPU  102 . The SRC  106  may also be located in the GPU  102 . In one exemplary embodiment, the GPU  102  and/or the South Bridge  304  can be part of the CPU  302 . 
       FIG. 3  illustrates additional components communicating with the embodiments illustrated in  FIGS. 1 and 2 .  FIG. 3  illustrates a proximity sensor  308 , a keyboard  310 , and a touchpad/sensor  312  connected to an Embedded Controller  306 . The Embedded Controller  306  and input devices, e.g., the proximity sensor  308 , the keyboard  310 , and touchpad/sensor  312  are each connected to standby power (also known as auxiliary power, suspend or wake power, etc.) so that during a system suspend, they can remain powered in standby and are able to supply inputs to the computer system during the system suspend or sleep mode. Furthermore, as illustrated in  FIG. 3 , the display panel  110 / 210  also receives standby power so that it remains powered under the herein described self-refresh mode. Therefore, even when the computer system has entered suspend, the input devices, the Embedded Controller  306 , the SRC  106  and SRC local frame buffer  108 , and display panel  110 / 210  can remain powered. As further illustrated in  FIG. 3 , the Embedded Controller  306  is also connected to a South Bridge  304  that is connected to a central processing unit (CPU)  302 , which is connected to the GPU  102  and display Panel  110 ,  210 . 
       FIG. 4  illustrates a data flow block diagram depicting the software and hardware interactions in an exemplary process for self-refreshing a display panel and putting a GPU into a sleep mode or power-down state in response to a detected period of activity. As illustrated in  FIG. 4 , conventional idle events (which can for example, result in the display panel dimming) can be detected by GPU drivers  302  and/or an Operating System (OS)  304 . As illustrated in block  308  of  FIG. 4 , when an idle event is detected (by the GPU drivers  302  or OS  304 ), and a graphical user interface (GUI)  306  has confirmed to the GPU drivers  302  that the user desires “visual continuity” (e.g., display device self-refresh without display dimming) then after a prescribed length of time, the “idle event” can result in the GPU drivers  302  beginning SRC initiation and eventually GPU sleep. In other words, whether initiated by the OS  304  or GPU drivers  302 , when an idle event has been detected, the idle event can be intercepted by the GPU drivers responsible for the display panel self-refreshing, and instead of dimming or powering down the display panel as the idle event was intended for, the self-refresh controller  106  can be activated instead, in accordance with embodiments of the present invention. 
     As illustrated in block  310  of  FIG. 4 , upon initiation of the self-refresh controller  106 , a SRC local frame buffer  108  captures display information from the GPU  102 , such that after the SRC local frame buffer  108  acquires current display information for the display panel  110 , the GPU  102  can be put to sleep, or placed in a reduced power setting. Optionally, the GPU  102  can also be powered down. With the GPU  102  in a sleep mode or powered down, the display panel  110  will be advantageously self-refreshed. With the GPU  102  powered down or in a sleep mode with reduced power settings, an equivalent amount of power can be advantageously conserved compared to periodically dimming the backlight or powering down the display panel  110  in response to the idle events. 
     In one embodiment, when the GPU  102  enters a sleep mode or is powered down, the communications link between the SRC  106  and the GPU  102  can also be dropped. Further, when the GPU  102  is put into a sleep mode or powered down, the GPU frame buffer  104  can also be powered down. In another embodiment, the GPU frame buffer  104  can optionally be kept in a self-refresh mode. 
     In a further embodiment, to enable the user to distinguish this mode of operation wherein the display is in self-refresh while the system is suspended, the system may place an icon or other graphical image on the screen, to allow the user to distinguish that even though the screen appears active that in fact a deeper power conservation state has been applied, or that the system has been placed in a suspend. This allows the user to understand that while in the suspended state, the system may respond more slowly. For example, when the keyboard or screen is touched, the suspended system may incur a one second delay to resume to normal operation and respond to the key that was pressed. 
     In one embodiment, the SRC local frame buffer  108  can be turned on only when it is time to capture a frame of display information. Such a time for turning on the SRC local frame buffer  108  would be when the GPU drivers  302  are ready to initialize the SRC  106 . Once the SRC local frame buffer  108  has been activated, it caches the current display information (e.g., a current frame) and is then ready to send the frame of display information to the SRC  106  when the SRC  106  is ready to begin self-refreshing the display monitor  110  after the GPU  102  has been placed in a sleep mode or powered down. 
     In another embodiment, entry into visual continuity can be contingent upon both a user preference in a graphical user interface (GUI) selection, as well as upon a detected user presence. In other words, “visual continuity” with GPU sleep or GPU shutdown will only be initiated after periods of activity provided the user has requested visual continuity and if a user is in fact detected. Therefore, even if the user has requested visual continuity, if a user is not actually present at the computer system, as determined by the exemplary proximity sensor  308 , then optionally, display panel self-refresh is not enacted and display panel dimming and eventual display panel power-down can be enacted instead, depending on user selected power management options. In other words, if a user is not detected, then a conventional phased sleep process can be used instead with display panel dimming and power-down. 
     An exemplary embodiment illustrated in  FIG. 3  provides a proximity sensor  308  to detect the presence of a user. In other embodiments, a user presence detection mechanism can be an infra-red sensor, a camera with image detection, or a capacitive touch sensor on the mouse, touchpad or notebook shell. In further embodiments, there is no proximity sensor and the decision whether to begin self-refreshing the display panel after an idle event will be contingent upon a user preference in the graphical user interface  306 . 
     In one embodiment, a faster entry into a suspend mode after a shorter interval of idleness may be applied as a system level policy change. Or in a further embodiment, the GPU driver  302  component may detect short durations of idleness, combined with a detected user presence and a GUI visual continuity selection, and begin self-refreshing the display panel  110  while powering down the GPU  102 . In one embodiment, display panel self-refresh and GPU sleep can be coupled with faster entry into a system suspend mode. As the system is placed in suspend, an application and GPU current state can be stored and the frame buffer contents also preserved, rather than evicted, allowing a faster resume (since the applications will not be forced to recreate their state). Such shorter time limits before entry into self-refresh modes results in self-refresh modes being utilized with shorter idle event time limits than seen in convention time limits before display panel dimming. Because of “visual continuity,” the idleness window can be kept short as compared to conventional dimming or display panel shutdown time limits. 
     In other words, system power management methods utilizing display panel self-refreshing provide “visual continuity” and allow a passive user to use the computer system without periodic input device interaction. Such use of “visual continuity” allows a much shorter idle time limit to be selected, as the display panel self-refresh mode will not distract the user. While a passive user might select a long idle event time limit for display panel dimming, a passive user can select a shorter idle event time limit for display panel self-refreshing which provides for visual continuity. 
     In a further embodiment, prior to entry into a deeper system off state (e.g., Hibernation S 4  or Shutdown S 5 ), the display may be caused to exit self-refresh, and after saving its current state as per the normal path, be completely powered down. 
     In another embodiment, the display monitor  110  can be self-refreshed even when the computer system is only momentarily idle. In other words, rather than using it only when a prescribed period of time of several seconds has elapsed, in one embodiment, the SRC  106  is used many times in a second so that there can be aggressive power management. In one exemplary embodiment, the display panel  110  can enter into a self-refresh mode twice a second. 
       FIG. 5  illustrates a data flow block diagram depicting the software and hardware interactions in an exemplary process for a computer system resuming normal operations after a user&#39;s actions, through one or more input devices, which results in the execution of a resume function. As illustrated in  FIG. 5 , when an input device  502  communicates a “user input,” the OS  304  receives the user input and the user input results in the OS  304  initiating a resume function, as illustrated in block  504 , which results in the GPU  102  powering back up, along with any associated communications link. As further illustrated in  FIG. 5 , with the GPU  102  waking up and able to resuming normal functionality, the self-refresh controller  106  and SRC local frame buffer  108  can be deactivated. 
     With the local frame buffer  108  deactivating and the GPU  102  reactivating, the GPU  102  resumes communicating display information to the display panel  110 . In one exemplary embodiment, approximately one second is required to exit a suspended system state and resume normal operations. In other words, there may be a slight delay between the time that an input device supplies an input signal to the computer system and the moment the computer system resumes. In other exemplary embodiments, the length of time required for the computer system to resume normal functionality will also be dependent upon the level of system suspension. The computer system will resume normal functionality faster when only the GPU  102  and communications link have to be powered up and returned to normal functionality, as opposed to resuming a computer system that had gone previously into a system suspend state. 
     In another exemplary embodiment, the user input devices, such as a keyboard/mouse  308  or touch pad/sensor  312 , or presence detection devices, such as the proximity sensor  308 , can trigger an early self-refresh exit, wake or system activation. In one embodiment, as illustrated in  FIG. 3 , these input devices, as well as the embedded controller  306  and display  110 , can remain powered even while the system is in a suspend state. As discussed above, even while the computer system is in a sleep mode, a “visual continuity” user selection will provide for display panel self-refreshing while powering down or sleeping the GPU. A system level embedded controller, keyboard or mouse controller, as illustrated in  FIG. 3 , remains powered to allow a user to interact with these input devices, even while the rest of the system is in a reduced power state such as a suspend state. When a key-click, mouse movement, or a touchpad press is detected by these controllers, a system event can be driven to cause a system level wake from S 3  suspend if applicable, or a GPU driver initiated GPU wake that exits the display panel from a self-refresh mode and returns the display panel to an active display. In one embodiment, the computer system can begin preemptively resuming normal operation when the system detects a user interacting with an input device. An example is a user touching a touchpad, wherein the touchpad detects the user&#39;s contact and recognizes that the user is about to touch the keyboard near the touchpad, allowing the system to start the resume operation, even before the actual “click” is performed. 
       FIG. 6  illustrates an on-screen system power management graphical user interface (GUI)  600 . The power management GUI  600  comprises several power management setting options. First is an option to dim the panel display  610  after a selected period of inactivity (e.g., seconds). As illustrated in  FIG. 6 , dimming the display panel  610  can be set to OFF. Second is an option to turn off the display panel  620  after a selected period of inactivity (e.g., minutes). As also illustrated in  FIG. 6 , turning off the display panel  620  can also be set to OFF. Third is an option to put the computer in a sleep mode  630  (e.g. suspend) after a selected period of inactivity (e.g., 1 Hour). Lastly, there is an option to provide the user with visual continuity  640  after the computer system has been inactive after a selected period of time  645 . As further illustrated in  FIG. 6 , a variety of time periods of inactivity  645  may be selected for activating visual continuity. As discussed herein, “visual continuity” settings provide improved GPU power conservation while providing the user visual continuity. 
     Various embodiments of the power management GUI  600  allow the user to select whether or not they wish to also dim  610  or turn off  620  the display panel  110  after selected periods of inactivity. In other embodiments, enabling visual continuity  640  can also automatically disable display panel dimming  610  and display panel power turn-off  620 . In one embodiment, the graphical user interface  600  can be part of the Operating System software (OS) itself, such that “visual continuity” can be a system feature that is selectable by the user in OS utility applications. In other words, the option would be in the OS  304  as part of traditional power saving options, or it could be in the power saving options seen in a device driver for the GPU  102  instead. 
       FIG. 7  illustrates a process for enabling display panel self-refresh with GPU sleep or power-down for power conservation. In step  702  of  FIG. 7 , an “idle event” is detected. In step  704  of  FIG. 7 , a determination is made as to whether or not the user has requested visual continuity. If the user has selected visual continuity, then in step  706  of  FIG. 7 , an optional determination is made as to whether or not a user is detected. Such detection can be performed by a proximity sensor  308  as illustrated in  FIG. 3 . If a user is detected in step  706 , then in step  708  of  FIG. 7 , self-refresh is initiated after an inactivity timer reaches a first prescribed time T 1 . As discussed, initiating display panel self-refresh can also power down or “sleep” the GPU  102  and the associated communications link. 
     In step  710  of  FIG. 7 , the computer system is put to sleep after the inactivity tinier reaches a fourth prescribed time T 4 , while the display panel  110  continues to be self-refreshed. In an optional step  712  of  FIG. 7 , the computer system can be put into Hibernation/Shutdown (S 4 /S 5 ) after the inactivity timer reaches a fifth prescribed time T 5 . As discussed above, if the computer system is placed into hibernation or shutdown while in self-refresh mode, the SRC  106  and SRC local frame buffer  108  are powered down as well as the rest of the computer as per the normal path the system takes for system hibernation or shutdown. As illustrated in  FIG. 7 , if in step  706 , it is determined that a user is not detected, then in step  714  of  FIG. 7 , self-refresh is initiated after the inactivity timer reaches the first prescribed time T 1 . In another embodiment, if a user is not detected in step  706 , self-refresh of the display panel is not activated and the process advances to step  716 . However, if self-refresh is initiated in step  714 , then a combination of traditional dimming and suspension modes in combination with display panel self-refresh with GPU Sleep will allow an even deeper power savings. 
     As illustrated in  FIG. 7 , after step  714  or after step  704 , when it is determined that visual continuity is not selected, in step  716  of  FIG. 7 , the display panel backlight is dimmed after the inactivity timer reaches a second prescribed time T 2 . In step  718  of  FIG. 7 , the display panel  110  is turned off after the inactivity timer reaches a third prescribed time T 3 . In step  720  of  FIG. 7 , the computer system is put into a suspend state after the inactivity timer reaches the fourth prescribed time T 4 . In step  722  of  FIG. 7 , the computer system is put into Hibernation/Shutdown (S 4 /S 5 ) after the inactivity tinier reaches the fifth prescribed time T 5 . 
       FIG. 8  illustrates a process for initiating display panel self-refresh for GPU power conservation. In step  802  of  FIG. 8 , self-refresh is initiated. In step  804  of  FIG. 8 , the local frame buffer  108  for a self-refresh controller  106  is activated. In step  806  of  FIG. 8 , a current frame with display information for the display panel  110  is captured from the GPU  102  in the SRC local frame buffer  108 . In step  808  of  FIG. 8 , the communications link between the GPU  102  and the self-refresh controller  106  is disabled. The GPU  102  is also powered down in step  808 . In step  810  of  FIG. 8 , the display panel  110  is self-refreshed from the SRC local frame buffer  108  as controlled by the SRC  106 . 
     In the aforementioned embodiments, some applications, such as VPN software, instant messaging, Internet download, or other applications, may exhibit negative user experience when the system is suspended. For example a VPN application may disconnect the network connection after system suspend, which would require the user to re-enter security information and key pass-code in order to re-establish the VPN connection. While this behavior is perfectly normal over a normal system suspend, this would present a disruptive experience when the user has selected visual consistency. 
     Another example is the system configuration option to select password lock on suspend. This option is typically provided by some operating systems to ensure that if the system is suspended that another person cannot illegitimately access it while left unattended. In this mode the screen contents are replaced with a non-descript background and a simple user interface is presented with the option to allow the user to return to the active desktop once the correct password is entered. If the system is placed in suspend with screen in self-refresh, then on resume the user would immediately see the lock out screen defeating the purpose of presenting a visually consistent experience. 
     In one embodiment, illustrated in  FIG. 9 , to prevent such a disruptive experience, a software agent  902  detects active applications or system configurations. The software agent  902  determines whether or not one or more known applications, or system configuration options, are present and active which could produce a negative impact on user experience while the user-selected power management state options are applied. 
     When the software agent  902  detects the potentially disruptive applications or system Configurations to be active the use of deeper power conservation from user-selected power management states  904  by the operating system  304  including suspend is disabled. As illustrated in  FIG. 9 , such application conflict checks can be performed by the software agent  902  and the result sent to the operating system  304  to enable or disable the above described deeper power conservation states  904 . Additionally the user may be presented with information regarding the inability to apply the user-selected power management mode  904  until the potentially disruptive programs are disabled or shut down. 
     In another embodiment the software agent  902  may disable such applications or system configurations so as to ensure that the system can go into suspend and resume without user noticeable disruption. 
     A user input through an interface, such as graphical user interface  306 , allows enabling suspend state in combination with self-refresh functionality (suspend-in-self-refresh) and subsequently allows selectable periodicity for the feature, from the rate in which the system will remain active and be placed in the suspended state. As discussed in detail below and illustrated in  FIG. 10 , from the periodicity, a time interval S 1  may be determined for which the system must have been idle before the system suspend state shall be applied. Since the display device may already be self-refreshed, entering suspend, enters the above mentioned suspend-in-self-refresh. A second interval S 2  may also be determined for which the system shall remain in said system suspend state before re-awakening. Lastly, a third time interval S 3  defines a time period for the system to remain awake to perform any work updates, and check for changes in user presence, before re-entering the system suspend state and repeating the process. 
     In another embodiment where a proximity sensor  308  is provided to detect the presence of a user, a fourth time interval S 4  may be entered when a user is not detected by the proximity sensor  308 , for which user absence for the duration of time interval S 4  shall cause the suspend in self-refresh to be abandoned and a return to the use of regular system suspend. 
     In one embodiment, as illustrated in  FIG. 9 , a timer  906  in the software agent  902  counts the first interval of idleness (S 1 ), which minimally includes a lack of user interaction, and may in one embodiment additionally include using a proximity detector  308  to detect that while inactive, the user is in fact still present in front of the device. In another embodiment the combination of user inactivity and the lack of any visible graphical activity may in combination be required before entering the suspend state. Upon detecting the required amount of idleness (S 1 ) the software agent  902  shall pass time interval setting S 2  to a timer function  908 , cause the display to be placed in self-refresh state, and cause the system to enter suspend. 
     As illustrated in  FIGS. 3 and 9 , the embedded controller  306  remains powered while the system is in the suspend state. In one embodiment this embedded controller  306  performs the timer function  908  counting the second interval S 2 , and upon expiration of the interval the embedded controller  306  triggers resume from system suspend. In another embodiment, the timing function  908  may be optionally provided by hardware that is also powered during system suspend. As also illustrated in  FIGS. 3 and 9 , the display panel  110 / 210  may also remain powered by standby power while in the suspend state to provide the herein described suspend-in-self-refresh state. 
     In another embodiment the embedded controller  306  can also detect activity from input devices that remain powered while in suspend, such as buttons, keyboard  310 , touch screen sensor  312 . While in the suspend-in-self-refresh state the activity on such user input devices may cause an immediate resume from the system suspend state. Upon resume from suspend the display exits the self-refresh state. 
     In one embodiment upon re-awakening from suspend-in-self-refresh the system software agent  902  shall detect the wake condition and if determined that this is the periodic resume from suspend-in-self-refresh the software agent  902  shall start a timer  906  using the third time interval S 3 . During this third time interval S 3  running applications may resume activity, perform regular updates and update their graphical on-screen content. Upon expiration of the timer interval S 3  the display  110  is again placed in self-refresh and the software agent  902  causes the system to re-enter the system suspend state. 
     In another embodiment the software agent  902  may additionally evaluate the proximity sensor  308  during the S 3  interval, and if no user presence is detected then increment a counter  910 , or alternatively if the user is present shall reset the counter  910 . On each subsequent re-awaken from suspend-in self-refresh the counter  910  is checked and if the count  910  has reached a first threshold, and the period of sleep or suspend is above another threshold, and thus the time the user has been absent has crossed a fourth threshold S 4 , indicating the user has not been present for a substantial time, the software agent  902  shall abandon use of suspend-in-self-refresh and shall instead proceed into normal system suspend. 
     Although certain preferred embodiments and methods have been disclosed herein, it will be apparent from the foregoing disclosure to those skilled in the art that variations and modifications of such embodiments and methods may be made without departing from the spirit and scope of the invention. It is intended that the invention shall be limited only to the extent required by the appended claims and the rules and principles of applicable law.