PATENT DOCUMENT

Publication Number: US-9116639-B2
Application Number: US-201213717978-A
Country: US
Kind Code: B2

Title: Maintaining synchronization during vertical blanking

Abstract:
Embodiments of an apparatus for implementing a display port interface are disclosed. The apparatus may include a source processor and a sink processor coupled through an interface. The interface may include a primary link, an auxiliary link, and a hot plug detect link. The source processor may be operable to send a wake-up command to the sink processor via the auxiliary link. The source processor may send initialization parameters to the sink processor via the primary link. The initialization parameters may include a clock data recovery lock parameter and an idle parameter. Following the initialization parameters, the source processor may send a synchronization signal to the sink processor via the primary link. The source processor may then send a sleep command via the primary link to the sink processor.

Claims:
What is claimed is: 
     
       1. An apparatus, comprising:
 a source processor; and 
 a sink processor coupled to the source processor through a primary link and an auxiliary link; 
 wherein the source processor is configured to:
 send a wake-up command to the sink processor via the auxiliary link; 
 negotiate one or more component capabilities of the sink processor via an interface that includes the primary link and the secondary link; 
 exchange one or more parameters with the sink processor dependent upon the one or more component capabilities; 
 send a plurality of initialization parameters to the sink processor via the primary link; and 
 send a synchronization signal to the sink processor via the primary link; 
 send a sleep command to the sink processor via the primary link responsive to the sending of the synchronization signal; 
 
 wherein the plurality of initialization parameters include a clock data recovery lock parameter, and an idle parameter. 
 
     
     
       2. The apparatus of  claim 1 , wherein the wake-up command includes a preamble, a wake with frequency change command, and a stop indicator. 
     
     
       3. The apparatus of  claim 1 , wherein the sink processor is configured to synchronize an internal timing circuit to an external timing reference responsive to the synchronization signal. 
     
     
       4. The apparatus of  claim 1 , wherein the clock data recovery lock parameter includes a number of clock recovery symbols needed for lock. 
     
     
       5. The apparatus of  claim 1 , further comprising a display coupled to the second processor. 
     
     
       6. A method, comprising:
 signaling a first end of operation from a first component to a second component on a primary link between the first component and the second component; 
 deactivating, in response to the signaling of the first end of operation, the primary link; 
 signaling a start of operation from the first component to the second component, wherein the signaling includes transmitting a command on a secondary link, and a plurality of parameters on the primary link; 
 negotiating, via an interface that includes the primary link and the secondary link, one or more component capabilities between the first component and the second component in response to signaling the start of operation; 
 exchanging one or more parameters between the first component and the second component dependent upon the one or more component capabilities; 
 activating the primary link responsive to the signaling of the start of operation and dependent upon the plurality of parameters; 
 sending, responsive to the activation of the primary link, a synchronization signal from the first component to the second component; 
 signaling, responsive to the sending of the synchronization signal, a second end of operation from the first component to the second component on the primary link; and 
 deactivating, in the response to the signaling of the second end of operation, the primary link; 
 wherein the plurality of parameters include a clock recovery lock parameter and an idle parameter. 
 
     
     
       7. The method of  claim 6 , wherein the command on the secondary link includes a preamble, a wake with frequency change command, and a stop indicator. 
     
     
       8. The method of  claim 6 , further comprising, acknowledging, by the second component, the transmitted command on the secondary link. 
     
     
       9. The method of  claim 6 , wherein the synchronization signal is a vertical synchronization signal. 
     
     
       10. The method of  claim 6 , wherein the clock data recovery lock parameter includes a number of clock recovery symbols needed for lock. 
     
     
       11. A system, comprising:
 a memory; 
 a first processor coupled to the memory; 
 a second processor coupled to the first processor through an interface; and 
 a display coupled to the second processor; 
 wherein the first processor is configured to:
 negotiate with the second processor one or more component capabilities of the second processor via the interface; 
 exchange one or more parameters with the second processor dependent upon the one or more component capabilities; 
 transmit a signal to the second processor to activate a low power mode of the interface; 
 transmit a signal to the second processor to deactivate the low power mode of the interface; 
 transmit a synchronization signal to the second processor responsive to the deactivation of the low power mode of the interface; 
 transmit a signal to the second processor to re-activate the lower mode of the interface responsive to the transmission of the synchronization signal. 
 
 
     
     
       12. The system of  claim 11 , wherein the interface comprises a primary link and an auxiliary link. 
     
     
       13. The system of  claim 12 , wherein transmit a signal to the second processor to deactivate the low power mode of the interface includes transmitting a command on the auxiliary link. 
     
     
       14. The system of  claim 13 , wherein to transmit the signal to the second processor to deactivate the low power mode of the interface further includes transmitting a plurality of initialization parameters on the primary link. 
     
     
       15. The system of  claim 11 , wherein the synchronization signal is a vertical synchronization signal. 
     
     
       16. A method, comprising:
 negotiating between a first processor and a second processor one or more component capabilities via an interface between the first processor to the second processor; 
 exchanging one or more parameters with the second processor dependent upon the one or more component capabilities; 
 activating a low power mode of the interface between the first processor and the second processor; 
 signaling, from the first processor to the second processor, an end to the low power mode; 
 deactivating the low power mode responsive to the signaling; and 
 sending, responsive to the deactivation of the low power mode, a synchronization signal from the first processor to the second processor; 
 re-activating the low power mode responsive to the sending of the synchronization signal. 
 
     
     
       17. The method of  claim 16 , wherein activating the low power mode of the interface comprises deactivating a primary link. 
     
     
       18. The method of  claim 16 , wherein signaling the end to the low power mode comprises sending a wake-up command through an auxiliary link from the first processor to the second processor. 
     
     
       19. The method of  claim 16 , wherein the synchronization signal is a vertical synchronization signal. 
     
     
       20. The method of  claim 16 , wherein deactivating the low power mode comprises sending a plurality of initialization parameters through the primary link from the first processor to the second processor. 
     
     
       21. A non-transitory computer accessible storage medium having program instructions stored therein that, in response to execution by a computer system, causes the computer system to perform operations including:
 signaling a first end of operation from a first processor to a second processor on a primary link between the first processor and the second processor; 
 deactivating, in response to the signaling of the first end of operation, the primary link; 
 signaling a start of operation from the first processor to the second processor, wherein the signaling includes transmitting a command on a secondary link, a plurality of parameters on the primary link; 
 negotiating one or more component capabilities between the first component and the second component in response to signaling the start of operation via an interface that includes the primary link and the secondary link; 
 exchanging one or more parameters between the first component and the second component dependent upon the one or more component capabilities; 
 activating the primary link responsive to the signaling of the start of operation and dependent upon the plurality of parameters; 
 sending, responsive to the activation of the primary link, a synchronization signal from the first processor to the second processor; 
 signaling, responsive to the sending of the synchronization signal, a second end of operation from the first processor to the second processor on the primary link; and 
 deactivating, in the response to the signaling of the second end of operation, the primary link; 
 wherein the plurality of parameters include a clock recovery lock parameter and an idle parameter. 
 
     
     
       22. The non-transitory computer accessible storage medium of  claim 21 , wherein the command includes a preamble, a wake with frequency change command, and a stop indicator. 
     
     
       23. The non-transitory computer accessible storage medium of  claim 21 , wherein the idle parameter includes a number of lines before active operation begins. 
     
     
       24. The non-transitory computer accessible storage medium of  claim 21 , wherein the synchronization signal is a vertical synchronization signal. 
     
     
       25. The non-transitory computer accessible storage medium of  claim 21 , the clock data recovery lock parameter includes a number of clock recovery symbols needed for lock.

Description:
BACKGROUND 
     1. Technical Field 
     This invention is related to the field of processor communication, and more particularly to the implementation of display port interfaces between processors. 
     2. Description of the Related Art 
     Display technology for computer systems continues to evolve. From the first Cathode Ray tubes (CRTs), new display technologies have emerged including Liquid Crystal Display (LCD), Light Emitting Diode (LED), Eletroluminescent Display (ELD), Plasma Display Panel (PDP), Liquid Crystal on Silicon (LCoS), for example. Additionally, computer systems may employ multiple displays, projectors, televisions, and other suitable display devices. 
     To support the growing number of display technologies and the need to connect to multiple displays, interface technologies between processors and displays have developed into complex systems that may support platform-independent operation, networked operation, “plug and play” connections, and the like. Additionally, new interface technologies, such as, e.g., High-Definition Multimedia Interface (HDMI), Video Graphics Array (VGA), Digital Visual Interface (DVI), or Embedded Display Port (eDP), may need to support legacy display types. In some cases, newer interface technologies may exploit the support for legacy display types by transmitting secondary data during time intervals, which are not utilized by legacy devices. 
     SUMMARY OF THE EMBODIMENTS 
     Various embodiments of an apparatus implementing a display port interface are disclosed. Broadly speaking, an apparatus and a method are contemplated in which a source processor and sink processor are coupled through an interface. The interface may include a primary link, an auxiliary link, and a hot plug detect link. The source processor may send a wake-up command to the sink processor over the auxiliary link. A plurality of initialization parameters may also be sent from the source processor to the sink processor over the primary link. The source processor may then send a synchronization signal to the sink processor. A sleep command may then be sent by the source processor to the sink processor in response to the sending of the synchronization signal. The initialization parameters may include parameters related to clock data recovery and an idle period. 
     In one embodiment, the wake-up command may include multiple parts. The wake-up command may include a preamble, a wake with frequency change command, and a stop indicator. 
     In a further embodiment, the sink processor is configured to synchronize an internal timing circuit to an external timing reference. The synchronization may be dependent on the synchronization signal. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The following detailed description makes reference to the accompanying drawings, which are now briefly described. 
         FIG. 1  illustrates an embodiment of a computing system. 
         FIG. 2  illustrates another embodiment of a computing system. 
         FIG. 3  depicts example waveforms illustrating an embodiment of a wake-up procedure. 
         FIG. 4  depicts example waveforms illustrating another embodiment of a wake-up procedure. 
         FIG. 5  depicts an example waveform illustrating a wake-up command. 
         FIG. 6  depicts a flowchart illustrating a method of a sleep and wake-up procedure. 
         FIG. 7  depicts a flowchart illustrating a method training a link. 
         FIG. 8  depicts a flowchart illustrating a method of adjusting changing a link clock frequency. 
         FIG. 9  depicts a flowchart illustrating a method of maintaining vertical synchronization. 
     
    
    
     While the disclosure is susceptible to various modifications and alternative forms, specific embodiments thereof are shown by way of example in the drawings and will herein be described in detail. It should be understood, however, that the drawings and detailed description thereto are not intended to limit the disclosure to the particular form illustrated, but on the contrary, the intention is to cover all modifications, equivalents and alternatives falling within the spirit and scope of the present disclosure as defined by the appended claims. The headings used herein are for organizational purposes only and are not meant to be used to limit the scope of the description. As used throughout this application, the word “may” is used in a permissive sense (i.e., meaning having the potential to), rather than the mandatory sense (i.e., meaning must). Similarly, the words “include,” “including,” and “includes” mean including, but not limited to. 
     Various units, circuits, or other components may be described as “configured to” perform a task or tasks. In such contexts, “configured to” is a broad recitation of structure generally meaning “having circuitry that” performs the task or tasks during operation. As such, the unit/circuit/component can be configured to perform the task even when the unit/circuit/component is not currently on. In general, the circuitry that forms the structure corresponding to “configured to” may include hardware circuits. Similarly, various units/circuits/components may be described as performing a task or tasks, for convenience in the description. Such descriptions should be interpreted as including the phrase “configured to.” Reciting a unit/circuit/component that is configured to perform one or more tasks is expressly intended not to invoke 35 U.S.C. §112, paragraph six interpretation for that unit/circuit/component. More generally, the recitation of any element is expressly intended not to invoke 35 U.S.C. §112, paragraph six interpretation for that element unless the language “means for” or “step for” is specifically recited. 
     DETAILED DESCRIPTION OF EMBODIMENTS 
     A computer system may include one or more functional blocks, such as, e.g., processors, memories, etc., coupled to a display. A dedicated processor or display controller may be coupled directly to the display and may control the flow of graphics data to the display from other processors within the computer system. Multiple displays with respective display controllers may be employed in some computer systems. 
     Specialized interfaces may be employed between processors and display controllers within a computer system. The interfaces may support multiple display types, and multiple numbers of display controllers and processors. Moreover, the interfaces may have modes of operation, which may allow for reduced power operation of the interface, and transmission of initialization or operation parameters from a processor to a display controller. 
     Computer System Overview 
     A block diagram of a computer system is illustrated in  FIG. 1 . In computer system  100 , processor  101  is coupled to memory block  103 , analog/mixed signal block  105 , I/O block  106 , and to processor  102 . Processor  102  is further coupled to display  104 . In various embodiments, computer system  100  may be configured for use in mobile computing applications such as, e.g., a tablet, a laptop computer or a cellular telephone. 
     Processors  101  and  102  may, in various embodiments, be representative of general-purpose processors that perform computational operations. For example, processors  101  and  102  may be central processing units (CPU) such as a microprocessor, microcontrollers, application-specific integrated circuits (ASICs), or field-programmable gate arrays (FPGAs). In some embodiments, processors  101  and  102  may implement any suitable instruction set architecture (ISA), such as, e.g., the ARM™, PowerPC™, or x28 ISAs, or a combination thereof. 
     Memory block  103  may include any suitable type of memory such as a Dynamic Random Access Memory (DRAM), a Static Random Access Memory (SRAM), a Read-only Memory (ROM), Electrically Erasable Programmable Read-only Memory (EEPROM), a FLASH Memory, or a Ferroelectric Random Access Memory (FeRAM), for example. It is noted that in the embodiment of a computer system illustrated in  FIG. 1 , a single memory block is depicted. In other embodiments, any suitable number of memory blocks may be employed. 
     Analog/mixed-signal block  105  may include a variety of circuits including, for example, a crystal oscillator, a phase-locked loop (PLL), an analog-to-digital converter (ADC), and a digital-to-analog converter (DAC) (all not shown). In other embodiments, analog/mixed-signal block  105  may be configured to perform power management tasks with the inclusion of on-chip power supplies and voltage regulators. Analog/mixed-signal block  105  may also include, in some embodiments, radio frequency (RF) circuits that may be configured for operation with cellular telephone networks. 
     I/O block  106  may be configured to coordinate data transfer between processor  101  and one or more peripheral devices. Such peripheral devices may include, without limitation, storage devices (e.g., magnetic or optical media-based storage devices including hard drives, tape drives, CD drives, DVD drives, etc.), audio processing subsystems, or any other suitable type of peripheral devices. In some embodiments, I/O block  106  may be configured to implement a version of Universal Serial Bus (USB) protocol or IEEE 1394 (Firewire®) protocol. 
     I/O block  106  may also be configured to coordinate data transfer between processor  101  and one or more devices (e.g., other computer systems or system-on-chips) coupled to processor  101  via a network. In one embodiment, I/O block  106  may be configured to perform the data processing necessary to implement an Ethernet (IEEE 802.3) networking standard such as Gigabit Ethernet or 10-Gigabit Ethernet, for example, although it is contemplated that any suitable networking standard may be implemented. In some embodiments, I/O block  106  may be configured to implement multiple discrete network interface ports. 
     Display element  104  may include any suitable type of display such as a Liquid Crystal Display (LCD), Light Emitting Diode (LED), Eletroluminescent Display (ELD), Cathode Ray Tube (CRT), Plasma Display Panel (PDP), Liquid Crystal on Silicon (LCoS), for example. Although a single display element is shown in the embodiment of a computer system illustrated in  FIG. 1 , in other embodiments, any suitable number of display elements may be employed. 
     Turning to  FIG. 2 , another embodiment of a computer system is illustrated. In computer system  200 , motherboard  201  is coupled to display panel  202  through display port  211 . Motherboard  201  includes video processor  203 , and display panel  202  includes display controller  209  and display  210 . In some embodiments, video processor  203  may correspond to processor  101  of computer system  100  as illustrated in  FIG. 1 , and display controller  209  may correspond to processor  102  of computer system  100  as illustrated in  FIG. 1 . 
     Video processor  203  includes display port source physical layer (PHY)  204 , and display controller  209  includes display port sink PHY  208 . In various embodiments, display port source PHY and display port sink PHY may implement any suitable display interface standard such as, High-Definition Multimedia Interface (HDMI), Video Graphics Array (VGA), Digital Visual Interface (DVI), or Embedded Display Port (eDP), for example. 
     Video processor  203  and display controller  209  may be implemented as dedicated processing devices. In various other embodiments, video processor  203  and display controller  209  may be implements as general purpose processors that are configured to executed program instructions stored in memory, such as memory block  103  of computer system  100  as illustrated in  FIG. 1 . 
     Display port  211  includes main link  205 , auxiliary link  206 , and hot plug detect (HPD) link  207 . As described below in more detail with reference to  FIG. 3  and  FIG. 4 , data may be transmitted from display port source PHY  204  to display port sink PHY  208  using main link  205 . Auxiliary link  206  may be used by either display port source PHY  204  or display port sink PHY  208  to transmit command signals. HPD link  207  may be used by display port source PHY  204  to detect the presence of display panel  202 . In various embodiments, bias resistors (not shown) may be coupled to HPD link  207 , and display port sink PHY  208  may include a pull-up device or a pull-down device coupled to HPD link  207  and configured to charge or discharge HPD link  207  to achieve the desired logic level. Any pull-up device or pull-down device may include one or more metal-oxide field-effect transistors (MOSFETs) 
     In some embodiments, main link  205  may include a data bus, consisting of multiple signal lines, that is configured to employ a clock data recovery (CDR) methodology. For example, data may be sent from source PHY  204  to sink PHY  208  without an accompanying clock signal. Sink PHY  208  may generate a clock signal based on an approximate frequency reference. The generated clock may then be phase aligned to transitions in the transmitted data using a phase-locked loop (PLL) or any other suitable phase detection circuitry. 
     In order to correct for drift in frequency of the PLL&#39;s oscillator, the transmitted data must contain a sufficient number of transitions to align the generated clock. The transmitted data may be encoded to ensure sufficient transitions. In some embodiments, the transmitted data may be encoded using 8B/10B, Manchester, or any other suitable type of encoding method. Although CDR was described above in the context of main link  205 , in various embodiments, all or part of the CDR method may be employed on auxiliary link  206  as well. 
     It is noted that “low” or “low logic level” refers to a voltage at or near ground and that “high” or “high logic level” refers to a voltage sufficiently large to turn on an re-channel MOSFET and turn off a p-channel MOSFET. In other embodiments, different technology may results in different voltage levels for “low” and “high.” 
     It is noted that the computer system illustrated in  FIG. 2  is merely an example. In other embodiments, different numbers of functional blocks and links, and different arrangements of functional blocks are possible and contemplated. 
     Display Port Operation 
     Example waveforms depicting the operation of a display port are illustrated in  FIG. 3 . Referring collectively to the computer system  200  illustrated in  FIG. 2 , and waveforms  300 , display port  211  may be in a sleep mode prior to time t 0 . During this time, display  210  may be in a period of vertical blanking and main link  205  may be inactive. 
     At time t 0 , source PHY  204  transmits wake-up command  310  on auxiliary link  206  to sink PHY  208 . Wake-up command  310  may include an indication that the frequency on main link  205  has changed and that clock recovery and lock may need to be performed. It is noted that in various embodiments, wake-up command  310  may be encoded using 8B/10B, Manchester-II, or any other suitable encoding method. Source PHY  204  also transmits operation parameter CR  306  on main link  205 . In some embodiments, operation parameter CR  306  may contain a number of clock recovery symbols to be used in sink PHY  208  to recover a clock from transmitted data. 
     Once operation parameter CR  306  has been transmitted, source PHY  204  transmits operation parameter symbol lock  307  at time t 1 . In some embodiments, symbol lock  307  may include the number of training pattern symbols required for sink PHY  208  to achieve symbol lock. The training pattern symbols may include TPS2 or TPS3 as defined in the Embedded DisplayPort (eDP) specification. 
     With the conclusion of the transmission of symbol lock  307 , source PHY  204  then transmits at time t 2 , operation parameter BS &amp; Idle  308 . In some embodiments, BS &amp; Idle  308  may include a number of lines before display  210  goes active. The lines sent to display  210  may include a blanking start framing symbol, or any other suitable framing symbol that may be sent to display  210  during an inactive period. 
     At time t 3 , source PHY  204  begins transmission of pixel packets  309 . The transmission of pixel packets may continue until another blanking period is initiated. The pixel packets may include packets relating to number of pixels in a horizontal line, the total number of lines in a video frame, horizontal and vertical synchronization widths, in addition to actual video data. 
     The waveforms and operation illustrated in  FIG. 3  are merely an example. In other embodiments, different commands and different orders of commands are possible. 
     Waveforms depicting the wake-up operation of a display port are illustrated in  FIG. 4 . Referring collectively to computer system  200  illustrated in  FIG. 2  and waveforms  400 , display port  211  may be in a sleep mode and display  210  may be in a horizontal or vertical blanking mode prior to time t 0 . In some embodiments, during the period of time prior to time t 0 , display  210  may in a self-refresh mode (commonly referred to as “panel self-refresh” or “PSR”) during which display controller  209  may rely on an internal PLL or other suitable timing reference circuit to send data to display  210 . Prior to time t 0 , the logical state of main link  205  may be a logical-1, a logical-0, or a high impedance state. When the state of a signal can be any allowable logic level, the value of the signal is commonly referred to as a “don&#39;t care.” 
     At time t 0 , source PHY  204  may issue wake-up command  411  via auxiliary link  206 . Wake-up command  411  may, in some embodiments, instruct sink PHY  208  to end a sleep or reduced power mode and enable receivers coupled to main link  205 . In various embodiments, wake-up command  411  may be encoded using 8B/10B, Manchester-II, or any other suitable encoding method. Source PHY  204  may also transmits initialization parameter CR  406  on main link  205 . In some embodiments, operation parameter CR  406  may contain a number of clock recovery symbols to be used in sink PHY  208  to recover a clock from transmitted data. 
     Once operation parameter CR  406  has been transmitted, source PHY  204  transmits initialization parameter symbol lock  407  at time t 1 . In some embodiments, symbol lock  407  may include the number of training pattern symbols required for sink PHY  208  to achieve symbol lock. The training pattern symbols may include TPS2 or TPS3 as defined in the Embedded DisplayPort (eDP) specification, or any other suitable training pattern. 
     With the conclusion of the transmission of symbol lock  407 , source PHY  204  then transmits at time t 2 , initialization parameter BS &amp; Idle  408 . In some embodiments, BS &amp; Idle  408  may include a number of lines before display  210  goes active. The lines sent to display  210  may include a blanking start framing symbol, or any other suitable framing symbol that may be sent to display  210  during an inactive period. 
     As described above, during the period prior to time t 0 , display controller  209  and display  210  may be performing self-refresh. While performing self-refresh, the timing reference of display controller  209  may loose synchronization with the timing reference of video processor  203 . When self-refresh mode is exited, visual artifacts (commonly referred to as “display tearing” or “screen tearing”) may be visible on display  210  due to the difference between the two aforementioned timing references. In some embodiments, synchronization signals may be sent between video processor  203  and display controller  209  to reduce differences between the timing references of the two components. 
     At time t 4 , source PHY  204  may transmit synchronization signal  409 . In some embodiments, synchronization signal  409  may a vertical synchronization signal that may be used to synchronize a PLL or other timing reference circuit in display controller  209  to the timing reference within graphics processor  203 . During vertical synchronization, display controller  209  may not send new graphics data to display  210  until the active refresh of display  210  is complete. 
     Once the transmission of synchronization signal  409  is complete, source PHY  204  may transmit sleep command  410 . In some embodiments, sleep command  410  may signal to sink PHY  208  to power-down input receivers associated with main link  205  to conserve power. Display  210  may remain in PSR or may also enter a reduced power mode. Once sink PHY  208  has entered a reduced power state, the logical state of main link  205  may be a logical “don&#39;t care.” 
     The waveforms and operation illustrated in  FIG. 4  are merely an example. In other embodiments, the wake-up operation may include different command or different numbers of commands, and different initialization or operational parameters may be employed. 
     Turning to  FIG. 5 , an example wake-up command is illustrated. In some embodiments, the wake-up command depicted in  FIG. 5  may correspond to wake-up command  310  as illustrated in  FIG. 3  or wake-up command  411  as illustrated in  FIG. 4 , and may be transmitted by a source PHY coupled to a display interface. Command  500  may be transmitted on an auxiliary link such as, auxiliary link  206  of display port  211  as illustrated in  FIG. 2 , for example, and may consist of one or more parts. 
     Prior to the beginning of the transmission of the command at time t 0 , the link may be pre-charged. In various embodiments, the link may be pre-charged to the power supply voltage, to a ground level, or to any suitable pre-charge voltage level. At time t 0 , the transmission of PREAMBLE  502  begins. In the illustrated embodiment, PREAMBLE  502  consists of eight consecutive logical-0 values (low logic levels), although in other embodiments, any suitable combination of logical-1 values and logical-0 values may be employed. 
     Once the transmission of the preamble is complete at time t 1 , the transmission of WAKE_F_CHANGE  503  begins. In command  500 , WAKE_F_CHANGE  503  includes a sequence of a logical-0 value followed by two logical-1 values, and a concluding logical-0 value. In various embodiments, different combinations of logical-0 values and logical-1 values may be employed to implement the WAKE_F_CHANGE command. The WAKE_F_COMMAND may, in some embodiments, indicate that the frequency on a primary link such as, e.g., main link  205  as illustrated in  FIG. 2 , has changed. 
     At time t 2 , the transmission of WAKE_F_CHANGE  503  concludes, and the transmission of STOP  504  begins. STOP  504  includes a sequence of two logical-1 values followed by two logical-0 values, although other combinations of logical values may be employed in different embodiments. Once the transmission of STOP  504  concludes at time t 3 , the transmission of command  500  is complete. 
     It is noted that the command illustrated in  FIG. 5  is merely an example. In other embodiments, different combinations of logical values and different command parts may be employed. 
     A flowchart illustrating a method of operating a display port such as, e.g., display port  211  as illustrated in  FIG. 2 , is depicted in  FIG. 6 . The method begins in block  601 . A termination of operation of the display port is then signaled from a display port source to a display port sink in block  602 . The termination of operation may be in order to enter a power savings mode. In some embodiments, the termination may be specific to a main or primary link of the display port, such as, main link  205  of display port  211  as depicted in  FIG. 2 . The signal of termination of operation may be transmitted on either a primary or auxiliary link of the display port. 
     The operation of a primary link may then be terminated in block  603 . In various embodiments, the termination may include the cessation of a portion of the primary link&#39;s operational capabilities. All of the operational capabilities of the primary link may be ceased in other embodiments. 
     In block  604 , the display port source transmits a signal to the display port sink to resume operation. In some embodiments, the signal to resume operation may be sent using an auxiliary link of the display port. The signal to resume operation may include multiple parts such as, e.g., command  500  as illustrated in  FIG. 5 . In various embodiments, additional commands or operational parameters, such as, a number of clock recovery symbols for clock data recovery, may be sent from the display port source to the display port sink before the transmission of data can resume. Such commands and parameters, such as those described above in reference to  FIG. 3  and  FIG. 4  may be sent via the primary link of the display port before the resumption of data transmission. 
     Once any additional command or operational parameters have been transmitted, normal operation of the display port may resume with the transmission of data (block  606 ). The method then concludes in block  607 . Although the various operations depicted in the method illustrated in  FIG. 6  are shown as being performed in a sequential fashion, in other embodiments, one or more of the operations may be performed in parallel. 
     Referring to  FIG. 7 , an example method of adjusting operation of a plurality of components through an interface is illustrated. The method begins in block  701 . The components connected through the interface then negotiate one or more component capabilities (block  702 ). In some embodiments, the negotiation may involve each of the plurality of components identifying each other as being compliant with an interface standard, such as, eDP, for example. 
     Once the negotiation is complete, the components may exchange one or more parameters (block  703 ). The exchanged parameters may include settings that govern the operation of the components, such as a data rate setting, or transceiver settings, for example. The operation of the components is then adjusted based upon the exchanged parameters (block  704 ). In various embodiments, the components may adjust their respective transceivers to adopt the data rate received during the exchange of parameters. Power consumption mode settings may also be adjusted in response to exchanged parameters. 
     The method illustrated in  FIG. 7  is merely an example. In other embodiments, different operations or different orders of operation are possible. 
     Turning to  FIG. 8 , a method of changing link clock frequency of a display port during a sleep or standby period is illustrated. The method begins in block  801  with the display port in a sleep or standby mode. A signal to resume operation may then be sent by the display port source to the display port sink (block  802 ). In some embodiments, the signal to resume operation may be sent via an auxiliary link of the display port. 
     Once the signal to resume operation has been transmitted, the display port source then sends a parameter to govern clock recovery of a new clock frequency (block  803 ). The parameter may include, in some embodiments, a number of clock recovery symbols necessary to perform clock data recovery. 
     The display port source may then send a number of symbols required for training of the link (block  804 ). In some embodiments, the symbols used for training may be specialized training symbols such as TPS2 or TPS3 as defined in the Embedded DisplayPort (eDP) specification. In other embodiments, any suitable training symbol pattern may be employed. 
     An idle parameter may then be sent from display port source (block  805 ). In some embodiments, the idle parameter may include a number of lines before resumption of active operation of a display coupled to the display port sink. The number of lines may, in various embodiments, refer to a number of framing symbols such as, e.g., the blanking start (BS) framing symbol as defined in the Embedded DisplayPort (eDP) specification. 
     With the completion of the transmission of the idle parameter, the display port source may then transmit pixel or graphics data to the display port sink (block  806 ). In some embodiments, the pixel or graphics data may include video data from one or more video sources such as, a Digital Versatile Disc (DVD), for example. The method then concludes (block  807 ). It is noted that the method illustrated in  FIG. 8  is merely an example. In other embodiments, different operations and different orders of operations are possible and contemplated. 
     A method for maintaining vertical synchronization on a display is illustrated in  FIG. 9 . The method begins in block  901  with a display port interface between a processor and a display controller in a sleep or low-power mode. During this time, the display controller and its associated display may be performing self-refresh. A signal to resume operation may then be sent by the processor to the display controller (block  902 ). In some embodiments, the signal to resume operation may be sent via an auxiliary link of the display port interface. 
     Once the signal to resume operation has been transmitted, the processor may then send a parameter to govern clock recovery by the display controller of a new clock frequency (block  903 ). The parameter may include, in some embodiments, a number of clock recovery symbols necessary to perform clock data recovery, and may be transmitted on a primary link of the display port interface. In other embodiments, the clock frequency may not change from a previous active period of the display port interface. 
     The processor may then send a number of symbols required for training of the link (block  904 ). In some embodiments, the symbols used for training may be specialized training symbols such as TPS2 or TPS3 as defined in the Embedded DisplayPort (eDP) specification, and may be sent on the primary link of the display port interface. In other embodiments, any suitable training symbol pattern may be employed to train the display port interface. 
     An idle parameter may then be sent from processor (block  905 ). In some embodiments, the idle parameter may include a number of lines before resumption of active operation of a display coupled to the display port sink. The number of lines may, in various embodiments, refer to a number of framing symbols such as, e.g., the blanking start (BS) framing symbol as defined in the Embedded DisplayPort (eDP) specification. In some embodiments, the idle parameter may be transmitted on the primary link of the display port interface. 
     With the completion of the transmission of the idle parameter, the processor may then send a synchronization signal to the display controller (block  906 ). In some embodiments, the synchronization signal may be a vertical synchronization signal, and may be employed by the display controller to adjust the phase and/or frequency of a timing reference circuit such as a PLL, for example. The phase and/or frequency of the timing circuit may be adjusted to match the phase and/or frequency of a timing reference circuit within the processor such as, e.g., a PLL or crystal oscillator. 
     Once the synchronization signal has been transmitted, the processor may then send a sleep or shutdown signal (block  907 ). In some embodiments, the sleep or shutdown signal may be sent on the primary link of the display port interface, and may signal the display controller to power-down receivers coupled to the primary link of the display port interface. The display controller and its associated display may remain in self-refresh mode after the receipt of the sleep or shutdown signal by the display controller. The method then concludes in block  907 . 
     It is noted that the operations depicted in the method illustrated in  FIG. 9  are shown as being performed sequentially. In other embodiments, all or some of the operations may be performed in parallel. 
     Numerous variations and modifications will become apparent to those skilled in the art once the above disclosure is fully appreciated. It is intended that the following claims be interpreted to embrace all such variations and modifications.

Metadata:
Filing Date: 20121218
Publication Date: 20150825
Grant Date: 20150825
Priority Date: 20121218
Inventors: TRIPATHI BRIJESH
Assignee: APPLE INC
CPC Classifications: [{"code": "G09G5/006", "inventive": true, "first": false, "tree": "[]"}, {"code": "G09G5/006", "inventive": true, "first": true, "tree": "[]"}, {"code": "G09G2370/047", "inventive": false, "first": false, "tree": "[]"}, {"code": "G09G2360/18", "inventive": false, "first": false, "tree": "[]"}, {"code": "G09G2330/021", "inventive": false, "first": false, "tree": "[]"}, {"code": "G09G2340/0435", "inventive": false, "first": false, "tree": "[]"}, {"code": "G09G5/008", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F1/12", "inventive": true, "first": true, "tree": "[]"}, {"code": "G09G5/12", "inventive": true, "first": false, "tree": "[]"}, {"code": "G09G2370/047", "inventive": false, "first": false, "tree": "[]"}, {"code": "G09G2370/10", "inventive": false, "first": false, "tree": "[]"}, {"code": "G09G2360/18", "inventive": false, "first": false, "tree": "[]"}, {"code": "G09G2330/021", "inventive": false, "first": false, "tree": "[]"}, {"code": "G09G2370/10", "inventive": false, "first": false, "tree": "[]"}, {"code": "G09G5/12", "inventive": true, "first": false, "tree": "[]"}, {"code": "G09G2340/0435", "inventive": false, "first": false, "tree": "[]"}, {"code": "G09G5/008", "inventive": true, "first": false, "tree": "[]"}, {"code": "G09G2330/021", "inventive": false, "first": false, "tree": "[]"}, {"code": "G09G2340/0435", "inventive": false, "first": false, "tree": "[]"}, {"code": "G09G5/008", "inventive": true, "first": false, "tree": "[]"}, {"code": "G09G5/12", "inventive": true, "first": false, "tree": "[]"}, {"code": "G09G5/006", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F1/12", "inventive": true, "first": true, "tree": "[]"}, {"code": "G09G2370/10", "inventive": false, "first": false, "tree": "[]"}, {"code": "G09G2370/047", "inventive": false, "first": false, "tree": "[]"}, {"code": "G09G2360/18", "inventive": false, "first": false, "tree": "[]"}]
Family ID: 49958667