Techniques to transmit commands to a target device

<u>FIELD</u>

0001The subject matter disclosed herein relates generally to techniques for regulating power consumption.

<u>RELATED ART</u>

0002Multimedia operations in computer systems are very common. For example, personal computers are often used to process and display video. Power consumption by computers is a concern. It is desirable to regulate power consumption by personal computers.

0003<patcit id="pcit0001" dnum="US2010123727A1"><text>US2010123727A1</text></patcit> discloses techniques to monitor a level of graphics processing activity and control power usage based on the level. When no graphics processing activity is detected for a period of time, then a timing controller for a display device is instructed to capture a current image and repeatedly display the captured image. The graphics processing devices can be powered down. When graphics processing activity is detected, the graphics processing devices are powered up and the components used to capture an image and display the captured image are powered down.

<u>SUMMARY OF INVENTION</u>

0004The present invention is defined in the independent claims. Preferred features are recited in the dependent claims

<u>BRIEF DESCRIPTION OF THE DRAWINGS</u>

0005Embodiments of the present invention are illustrated by way of example, and not by way of limitation, in the drawings and in which like reference numerals refer to similar elements. <ul id="ul0001" list-style="none" compact="compact"><li><figref idref="f0001">FIG. 1A</figref> depicts a system in accordance with an embodiment.</li><li><figref idref="f0001">FIG. 1B</figref> depicts an example of components of a host system whose power consumption can be controlled, in accordance with an embodiment.</li><li><figref idref="f0002">FIG. 1C</figref> depicts a high level block diagram of a timing controller for a display device in accordance with an embodiment.</li><li><figref idref="f0003">FIG. 2</figref> depicts an example format of signals transmitted over multiple lanes of a DisplayPort interface.</li><li><figref idref="f0004">FIG. 3</figref> depicts an example manner of communication of secondary data packets over one and more lanes of a DisplayPort interface.</li><li><figref idref="f0005">FIG. 4</figref> depicts an example of a sequence of events for entry into main link standby mode.</li><li><figref idref="f0005">FIG. 5</figref> depicts an example of a sequence of events for exit from main link standby mode.</li></ul>

<u>DETAILED DESCRIPTION</u>

0006Reference throughout this specification to "one embodiment" or "an embodiment" means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, the appearances of the phrase "in one embodiment" or "an embodiment" in various places throughout this specification are not necessarily all referring to the same embodiment. Furthermore, the particular features, structures, or characteristics may be combined in one or more embodiments.

0007<figref idref="f0001">FIG. 1A</figref> depicts a system 100 in accordance with an embodiment. System 100 may include a source device such as a host system 102 and a target device 150. Host system 102 may include a processor 110 with one or more cores, host memory 112, storage 114, and graphics subsystem 115. Chipset 105 may communicatively couple devices in host system 102. Graphics subsystem 115 may process video and audio. System 100 can be implemented in a handheld personal computer, mobile telephone, set top box, or any computing device. Any type of user interface is available such as a keypad, mouse, and/or touch screen.

0008In accordance with various embodiments, processor 110 may execute a software driver (not depicted) that determines whether to (1) instruct target device 150 to capture an image and repeatedly display the captured image, (2) power down components of graphics subsystem 115, and (3) power down components of target device 150. The driver may determine whether to initiate actions (1), (2), or (3) based at least on: a change in the system timer period, triangle or polygon rendering, any processor core is not in low power mode, any mouse activity, vertical blanking interrupts are used, and/or overlay is enabled. For example, powering down components may involve reducing voltage regulators to the lowest operating voltage level. For example, when the processor 110 executes a Microsoft Windows compatible operating system, the driver may be a kernel mode driver.

0009For example, host system 102 may transmit commands to target device 150 using interface 145. In some embodiments, interface 145 may include a Main Link and an AUX channel, both described in Video Electronics Standards Association (VESA) DisplayPort Standard, Version 1, Revision 1a (2008) as well as revisions and variations thereof. In various embodiments, host system 102 (e.g., graphics subsystem 115) may form and transmit communications to target device 150 at least in a manner described with respect to co-pending <patcit id="pcit0002" dnum="US28619208" dnum-type="L"><text>U.S. patent application having Ser. No. 12/286,192, entitled "Protocol Extensions in a Display Port Compatible Interface," inventors Kwa et al., filed Sep. 29, 2008</text></patcit>.

0010Target device 150 may be a display device with capabilities to display visual content and/or render audio content. For example, target device 150 may include control logic such as a timing controller (TCON) that controls writing of pixels as well as a register that directs operation of target device 150. Target device 150 may have access to a memory or frame buffer from which to read frames for display.

0011Various embodiments include the capability to transmit secondary data packets over interface 145 to target device 150. Secondary data packets can be used to command target device 150.

0012<figref idref="f0001">FIG. 1B</figref> depicts an example of components of host system 102 whose power consumption can be controlled (e.g., power consumption decreased or increased), in accordance with an embodiment. The components can be in a chipset, processor, or graphics subsystem. For example, the display phase lock loop (PLL) 160, display plane 162, display pipe 164, and display interface 166 of host 102 can be powered down or up. PLL 160 may be a system clock for the display plane 162, display pipe 164, and/or display interface 166. For example, display plane 162 may include a data buffer and RGB color mapper, which transforms data from buffer to RGB. Display plane 162 may include an associated memory controller and memory input/output (IO) (not depicted) that could also be power managed. Pipe 164 may include a blender of multiple layers of images into a composite image, X, Y coordinate rasterizer, and interface protocol packetizer. The interface protocol packetizer may be compliant at least with Display Port or Low-voltage differential signaling (LVDS), available from ANSI/TIA/EIA-644-A (2001), as well as variations thereof. Display interface 166 may include a DisplayPort or LVDS compatible interface and a parallel-in-serial-out (PISO) interface.

0013<figref idref="f0002">FIG. 1C</figref> depicts a high level block diagram of a timing controller for a display device in accordance with an embodiment. Timing controller 180 has the capability to respond to instructions from a host device to enter a self refresh display (SRD) mode that may include powering down components and/or capturing an image and repeatedly outputting the captured image to a display. In response to signal SRD_ON from a host, SRD control block activates the frame buffer to capture a frame and the SRD control block controls the multiplexer (MUX) to transfer the captured frame to the output port. After the frame buffer captures a frame, the host may read a register in the panel that indicates that the capture has taken place and that the timing controller displays a captured image. After the signal SRD_ON is deactivated, SRD control block deactivates the frame buffer and associated logic and causes the MUX to transfer incoming video from the input port (RX in this case) to the output port (TX). Timing controller 180 may use less power because the frame buffer is turned off and the logic clock gated when the self refresh display mode is exited. In various embodiments, SRD_ON and SRD_STATUS can be signals or configured in a register.

0014<figref idref="f0003">FIG. 2</figref> depicts an example format of signals transmitted over multiple lanes on a DisplayPort compatible interface. In particular, <figref idref="f0003">FIG. 2</figref> reproduces <figref idref="f0003">FIG. 2</figref>-14 of the Video Electronics Standards Association (VESA) DisplayPort Standard, Version 1, Revision 1a (2008) (hereafter DP1.1a specification"). However, embodiments of the present invention can be used in any version and variation of DisplayPort as well as other standards. DisplayPort specifies the availability of secondary data packets to transmit information at the vendor's discretion. Vendor-specific extension packets are a type of secondary data packet that can be used to control the display self refresh functionality over embedded DisplayPort (eDP). The basic structure of the header information for these secondary data packets is described in table 2-33 of section 2.2.5 of the DP1.1a specification, which is reproduced below in table 1. <tables id="tabl0001" num="0001"><table frame="all"><title>Table 1</title><tgroup cols="2"><colspec colnum="1" colname="col1" colwidth="14mm" align="center" /><colspec colnum="2" colname="col2" colwidth="70mm" align="center" /><thead valign="top"><row><entry>Byte#</entry><entry><b>Content</b></entry></row></thead><tbody><row><entry>HB0</entry><entry>Secondary-data Packet ID</entry></row><row><entry>HB1</entry><entry>Secondary-data Packet type</entry></row><row><entry>HB2</entry><entry>Secondary-data-packet-specific header byte0</entry></row><row><entry>HB3</entry><entry>Secondary-data-packet-specific header byte1</entry></row></tbody></tgroup></table></tables>

0015<figref idref="f0004">FIG. 3</figref> depicts an example manner of communication of secondary data packets over one and more lanes of DisplayPort. In particular, <figref idref="f0004">FIG. 3</figref> reproduces <figref idref="f0003">FIG. 2</figref>-24 of the DP1.1a specification. As shown, secondary data packets can include header bytes, parity bytes, and data bytes.

0016In accordance with various embodiments, the following table provides an example of commands that can be transmitted in header bytes of secondary data packets, in accordance with various embodiments. Commands can be performed by a target device such as a display with capability to perform self refresh display. <tables id="tabl0002" num="0002"><table frame="all"><title>Table 2</title><tgroup cols="2"><colspec colnum="1" colname="col1" colwidth="14mm" /><colspec colnum="2" colname="col2" colwidth="106mm" /><thead valign="middle"><row><entry>Byte#</entry><entry>Example of Contents</entry></row></thead><tbody valign="middle"><row rowsep="0"><entry morerows="1" rowsep="1">HB0</entry><entry>OOh: Revision 0 (Haswell generation)</entry></row><row><entry>All other values reserved</entry></row><row><entry>HB1</entry><entry>04h (extension packet type indicator as defined by DP1.1a specification)</entry></row><row rowsep="0"><entry morerows="1" rowsep="1">HB2</entry><entry>Bits 0-2 used for controls</entry></row><row><entry>Bits 7:3 = Reserved (all 0's)</entry></row><row><entry>HB3</entry><entry>Reserved (all 0's)</entry></row></tbody></tgroup></table></tables>

0017Various embodiments provide controls in bits 0-2 of header byte HB2. Table 3 describes example commands in bits 0, 1, and 2 in header byte HB2. <tables id="tabl0003" num="0003"><table frame="all"><title>Table 3</title><tgroup cols="2"><colspec colnum="1" colname="col1" colwidth="37mm" /><colspec colnum="2" colname="col2" colwidth="129mm" /><thead valign="middle"><row><entry>Control Field Bit</entry><entry>Definition</entry></row></thead><tbody valign="middle"><row rowsep="0"><entry morerows="1" rowsep="1">B0: Frame Type</entry><entry>B0 = 0 means current frame is identical to the one previously sent.</entry></row><row><entry>B0 = 1 means current frame is different from the previously sent frame.</entry></row><row rowsep="0"><entry morerows="2" rowsep="1">B1: Source SRD State</entry><entry>Source SRD state control field indicates the source's display controller state, which is used as a command by the target device to manage its local controller.</entry></row><row rowsep="0"><entry>B1 = 0 means SRD_Off. Source state is such that normal display processing occurs and the eDP link remains active.</entry></row><row><entry>B1 = 1 means SRD_On. Source state is such that normal display processing may be disabled and the eDP link may be placed in standby.</entry></row><row rowsep="0"><entry morerows="1" rowsep="1">B2: Link Standby Enable</entry><entry>B2 = 0 means main link to remain in normal active state.</entry></row><row><entry>B2 = 1 enables main link to enter standby state.</entry></row></tbody></tgroup></table></tables>

0018Bit B0 indicates whether a frame to be sent to a target device has not changed from a previous frame that was sent to the target device. Bit B0 indicates whether a target device is to store an incoming image in a buffer. The target device can be a display with capability to enter self refresh display mode and display an image from a buffer. Bit B0 can be used where an application is to update an image on a display. An update can be made to wakeup a panel and tell the panel that one or more modified frame(s) are to be transmitted to the display and to store the frames. After storing the frames, the display and display system can return to low power state and the display system can use the updated frame for self refresh display.

0019Bit B1 indicates whether the target device is to enter self refresh display mode or remain in normal operation. Bit B1 also indicates whether normal display processing occurs and the link between the source and target device remains in normal active state.

0020Bit B2 indicates whether to power down a main link. For example, the main link can be a differential pair wire having connectors, d+ and d-. The link can transmit RGB content or other types of content. The link can be powered down or enter lower power mode.

0021Standard Embedded DisplayPort implementations support two link states: (1) full on ("Normal Operation") in which video data is transmitted to a panel and (2) full off ("ML Disabled") in which a lid is closed on a laptop and the display interface is turned off because video is not required. The standard Embedded DP implementation also supports an intermediate set of training-related transitional states. SRD adds an additional state: "ML Standby." State "ML Standby" enables a receiver to implement additional power management techniques for additional power reductions. For example, a receiver bias circuitry and PLLs can be turned-off. For example, components described with regard to <figref idref="f0001">FIG. 1B</figref> can enter lower power state or turn-off. State "ML Standby" can turn off a display interface and display link but use an image stored in panel for SRD.

0022<figref idref="f0005">FIG. 4</figref> depicts an example of a sequence of events for entry into ML standby mode. A DisplayPort main link can be used to transmit signals X, Y, and Z. In some embodiments, header byte HB2 can be used to transmit signals X, Y, and Z. Signal X represents whether the current frame, that is to be transmitted after a VBI, is modified or unmodified relative to a previously transmitted frame. In this example, the value of signal X can indicate that the current frame is modified or unmodified relative to the previously transmitted frame. In this example, it does not matter whether frame is modified or unmodified. Signal Y indicates whether SRD is on or off. In this case, signal Y indicates that SRD state is ON. Signal Z indicates whether a link standby entry is to occur. In this case, signal Z indicates link standby is to be entered.

0023In some embodiments, header byte HB2 can be used to transmit signals X, Y, and Z. To transmit X, Y, and Z, the following scheme can be used: bit B0 represents X, bit B 1 represents Y, and bit B2 represents Z.

0024Segment "Active" can include RGB color data for transmission to a display. Segment "BS" can indicate a start of a vertical blank interval in the system. Segment "BS to stdby" indicates a delay between a start of a vertical blank interval and a start of standby mode.

0025<figref idref="f0005">FIG. 5</figref> depicts an example of a sequence of events for exit from ML standby mode. In particular, states of the main link and auxiliary channel are described. The main link state is in state "Standby." The source initiates ML Standby exit using an AUX channel to transmit a write operation. Command WR can be used to write to register address location 00600h to wake up the target device and cause the target device to exit ML standby mode. Other register address locations can be used. The target device monitors location 00600h and wakes up on reading a wake up command in that location. After some delay, the target device transmits command ACK to the host using an AUX channel to indicate acknowledgement of receipt of the WR command. The length of the delay between receipt of WR and transmission of ACK can be defined by the DisplayPort Specification.

0026On detecting the write event, the target device power-ups the main link receiver and re-enters the training state to be ready for link training. Accordingly, as shown, the main link enters the state "Training." Re-entering the training state after exiting standby mode without explicit command provides faster synchronization. After the source completes sending the write transaction, the source may initiate link training. The transmitter may initiate either full training or Fast Link Training as described in the DP specification. A target device could be turned off and lose awareness of need to train when it wakes up. Causing the target device to train immediately after exiting standby allows full power down of a DP receiver.

0027The graphics and/or video processing techniques described herein may be implemented in various hardware architectures. For example, graphics and/or video functionality may be integrated within a chip set. Alternatively, a discrete graphics and/or video processor may be used. As still another embodiment, the graphics and/or video functions may be implemented by a general purpose processor, including a multicore processor. In a further embodiment, the functions may be implemented in a consumer electronics device.

0028Embodiments of the present invention may be implemented as any or a combination of: one or more microchips or integrated circuits interconnected using a motherboard, hardwired logic, software stored by a memory device and executed by a microprocessor, firmware, an application specific integrated circuit (ASIC), and/or a field programmable gate array (FPGA). The term "logic" may include, by way of example, software or hardware and/or combinations of software and hardware.

0029Embodiments of the present invention may be provided, for example, as a computer program product which may include one or more machine-readable media having stored thereon machine-executable instructions that, when executed by one or more machines such as a computer, network of computers, or other electronic devices, may result in the one or more machines carrying out operations in accordance with embodiments of the present invention. A machine-readable medium may include, but is not limited to, floppy diskettes, optical disks, CD-ROMs (Compact Disc-Read Only Memories), and magnetooptical disks, ROMs (Read Only Memories), RAMs (Random Access Memories), EPROMs (Erasable Programmable Read Only Memories), EEPROMs (Electrically Erasable Programmable Read Only Memories), magnetic or optical cards, flash memory, or other type of media/machine-readable medium suitable for storing machine-executable instructions.

0030The drawings and the forgoing description gave examples of the present invention. Although depicted as a number of disparate functional items, those skilled in the art will appreciate that one or more of such elements may well be combined into single functional elements. Alternatively, certain elements may be split into multiple functional elements. Elements from one embodiment may be added to another embodiment. For example, orders of processes described herein may be changed and are not limited to the manner described herein. Moreover, the actions of any flow diagram need not be implemented in the order shown; nor do all of the acts necessarily need to be performed. Also, those acts that are not dependent on other acts may be performed in parallel with the other acts. The scope of the present invention, however, is by no means limited by these specific examples. Numerous variations, whether explicitly given in the specification or not, such as differences in structure, dimension, and use of material, are possible. The scope of the invention is defined by the following claims.