USB 3.0 Software Architecture and Implementation Issues. Terry Moore, CEO MCCI Corporation

Transcription

1 USB 3.0 Software Architecture and Implementation Issues Terry Moore, CEO MCCI Corporation

2 Agenda Introducing MCCI USB 3.0 from a Software Perspective USB 3.0 Software Challenges New Device Classes Conclusion

3 Introducing MCCI

4 About MCCI World Leader in USB technology, system engineering specialists since 1995 Worldwide headcount: 85 Focused on cell phone industry Over 600 million products use MCCI technology Two of the top five handset vendors Three of the top five handset platform vendors Additional market base in set-top boxes, car navi systems Test services reinforce system capabilities One of 5 USB-IF certified test houses world-wide Microsoft WHQL test services One of two ExpressCard test houses

5 MCCI Worldwide Development Sites Sales / Support Sites

6 MCCI USB Product Offering End to End Solutions for USB 2.0 and 3.0 Embedded Device/Host/OTG Applications (MTP, PictBridge) Windows Host Drivers for xhci Class drivers for Windows, Mac OS X, Linux Development and Test Tools MCCI USB DataPump - Embedded USB Device/Host/OTG, classes, protocols and applications Development, Test, and Validation Tools USB 2.0 and 3.0 Host Stack and class drivers for Windows, Mac OS X, Linux

7 MCCI Strengths Total System Knowledge End-to-End USB Offering High Volume Quality World-Wide Support Team

8 USB 3.0 from a software perspective

9 USB 3.0 System Concepts

10 USB3.0 Technology Availability First products will ship in 2H2009 Initial deployment in storage devices (HDD, SSD) Early products will use third-party xhci host stack Microsoft host stack will not ship before Win 7 SP1, approximately one year after Win 7 launch Microsoft host stack availability will be based on having a variety of device classes and hosts to test with

11 Host PC (Win2K/XP/Vista/Win7) File-systems and Applications Video Display Function Driver Function UASP BOT Host Drivers Host Function Function Driver Driver USB 3.0 Host Stack xhcd (host controller driver for xhci) OS Kernel / HAL xhci Host Controller Devices Hard Hard Drive Drive UAS Hard Flash Video Drive Disk Display Application Application Application Video UASP Device Protocol UASP UASP BOT Display Device Device Class Protocol Protocol Device Protocol MCCI MCCI USB USB DataPump DataPump MCCI USB USB USB DataPump Device Device Stack Stack 3.0 Devices Device Device Device Controller Controller Controller Driver Driver Driver RTOS RTOS RTOS Kernel Kernel Kernel / HAL / HAL / HAL USB 3.0 USB USB SuperSpeed/Legacy SuperSpeed Device Device Device Controller Controller Controller USB (SuperSpeed, Legacy) USB Software Other Software Hardware

12 USB 3.0 Software Challenges

13 xhci Key Software Issues Single controller supports low, full, high and super speeds Scheduling and bus management handled internally EHCI operates by processing linked lists in system memory EHCI continually accesses system memory to keep USB bus running, even when there s no data to move xhci operates on lists held internally No system memory accesses needed to keep bus running, until data must be moved xhci can achieve much lower system power, but system software must change (even for high/full/low speed)

14 Changes to host system software Speeds at root hub Legacy: companion controllers: one root hub for each speed xhci: only one host controller model for all speeds one root hub for all speeds Enumeration and address assignment EHCI: system software must do every step xhci: host controller does the work legacy stack must change Bandwidth allocation (interrupt / isochronous) EHCI: system software must build schedule xhci: host controller builds schedule legacy stack must change USB3 hubs are combinations of legacy hubs and Super Speed hubs User interface may need to reflect this

15 xhci Host Stack Integration Issues Test tools are needed to exercise these interfaces during product validation Any proprietary extensions, configurations, etc. to the xhci controller will need to be customized in the xhci Host Controller Driver

16 Device-Side Changes USB 3.0 adds SuperSpeed 400 MB/sec theoretical max Requires efficient hardware Flexible DMA engine with scatter/gather and good support for short/zerolength packets Minimize software intervention for ordinary things Requires efficient software Zero copy architecture Minimize round trips Careful CPU cache management Able to tune for bus bandwidth and interrupt mitigation, so that SuperSpeed USB can co-exist with other applications Debugging with printf() will be difficult

17 USB 3.0 Streams High throughput may require out-of-order operation Disk drives are the obvious example Inconvenient on USB 2 because the data over a given endpoint is just sequential. Software has to get involved to set up buffers USB 3.0 Streams allow many requests to be sent over a single endpoint concurrently Concurrent requests can be completed by the data source in any convenient order No software intervention is needed at the time data becomes available data flows directly to the buffer associated with the request USB 3.0 system APIs must be extended to allow a Stream ID to be associated with a given request

18 Challenges for Embedded Systems Memory footprint for xhci Memory footprint for streams Power consumption Internal bus transactions SDRAM transactions USB activity

19 Legacy Issues (Devices) Devices have to work with USB 2.0 hosts This will be major use case for next year or two! Must include production-quality USB 2.0 device controller hardware If USB 2.0 controller hardware is not integrated with Super Speed hardware, then may need two software stacks Devices have to disconnect from legacy when Super Speed connect is detected Need to pass USB 2.0 logo test (even though there s no USB 3.0 test yet)

20 Legacy Issues (Hosts) USB 3.0 hubs are similar to, but not identical to, USB 2.0 hubs Finite state machines and control operations are different Adding USB 3.0 support to an existing USB 2.0 hub driver may destabilize the USB 2.0 driver Early hubs will have bugs Legacy enumeration is different when working with xhci TT support is substantially different Enumeration of legacy devices is different Billions of legacy devices shipped Test matrix is huge

21 New Device Classes for USB

22 UAS: USB Attached SCSI In order to get maximum benefit of USB 3.0, the mass storage protocol has to be improved Current BOT (Bulk Only Transfer) protocol doesn t allow overlapped operations and out-of-order completion BOT doesn t match modern SCSI architecture ANSI T.10 SAM-4 (SCSI Architecture Model 4) SAS (Serial Attached SCSI) UAS (USB Attached SCSI)

23 UAS and UASP UAS is a full-fledged mapping of SCSI onto USB UAS relates USB bus events to SCSI bus events UAS is designed to take advantage of USB 3.0 streams For USB 2.0, throughput increases by up to 50% Data transport and overlapped commands are handled differently for USB 2.0 speed UAS Protocol (UASP) covers the differences in how UAS is mapped onto USB 3.0 and USB 2.0; the architecture is identical UAS is being developed by T.10, UASP is being developed by the USB-IF DWG, they are defining the differences

24 Video Display Class USB 3.0 is fast enough to carry full HD uncompressed New workgroup at USB-IF is developing a standard device class Use cases PC or STB host streaming HD content Mobile device streaming MP-4 content Mobile or embedded device using USB display for user interface Publication probably in early

25 Conclusion

26 Conclusion xhci Architecture New host architecture brings increased complexity, key to improved power management Host stack requires extensive test infrastructure to ensure reliability through comprehensive corner-case testing Legacy Support There is more complexity because end users want to maintain their investment in USB2.0 products USB Attached SCSI, Streams Needed to take full advantage of USB3.0 capabilities UASP Specification not yet ratified

27 Thank you!

28 Supplemental slides

29 MCCI USB DataPump A complete embedded USB 3.0 Host/Device stack for cell-phones and other intelligent products. USB Device Features USB 3.0 SuperSpeed, High Speed, Full Speed Multi-function, multi-mode Audio. Video and HID (web cam, VoIP) CDC ECM, EEM and NCM for TCP/IP CDC ACM, WMC and MCPC GL-004/005 for multi-function cell-phones. Mass Storage UAS and BOT Still Image Class (PictBridge, MTP) Device Firmware Update (DFU), for firmware update over USB Various special purpose and custom protocols USB Host/OTG Features Hub Composite (for multi-function devices) ACM/WMC OBEX Mass Storage HID USBSIM Classes (UICC, EEM) Portable across CPUs, little/big-endian, HW platforms, OS, compilers, development platforms

30 Windows Drivers MCCI provides all the software necessary to use a USB 3.0 SuperSpeed device on Windows xhci Host Controller Driver Hub Driver Composite Driver UASP Driver for Hard Drives Support Windows 2000, XP, Vista, Windows 7 Support all existing USB 2.0 devices and their drivers Support all existing device classes

31 USB 3.0 SuperSpeed Advantages 10x throughput increase vs USB2.0 (480Mbps -> 5Gbps) cable length reduced to 3M max Backwards compatible USB 2.0 devices will continue to work, and new devices work with old systems Same USB device model and pipe model Host class drivers should work immediately with Super Speed Power efficient especially on host, but devices can also benefit Future improvements Existing design can support 25Gbps link speeds Proven basis Signaling based on PCIe and SATA

32 Other features More power for super-speed devices Up to 900mA (USB 2.0 maximum 500mA) Powered B connector allows self-powered devices to power external accessories (e.g., wireless adapters) Streaming High throughput benefits from out-of-order operations Multiple concurrent requests over single endpoint Beneficial for disk drives, media