> > > > We are working with a host controller on a PowerPC embedded board. It is > > an EHCI host controller. However, there are no UHCI/OHCI host > > controllers on the board. Therefore, if a FS/LS device plugs onto the > > board, Linux will try to hand the port to a companion controller, which > > is not there, and this causes the EHCI host controller die (or maybe the > > port is marked dead?), and unplug the device causes no "disconnect" > > report. The host controller also does not respond to further plug in of > > a HS device. > > > Hi, > > Are you sure of these facts? It would be a gross violation of the USB > spec to not fall back to fs for a high speed device, or to not support > LS at all. It means you cannot use FS hubs etc. One of the goals of > the USB spec is that you should be able to plug any device with a > compatible plug and it will work. Maybe they assume you will solder a > HS hub to the motherboard, and let the hub TTs handle the other > speeds? Even that could lead to flakey failures where sometimes the > USB bus would work and other times fail completely, where normally the > bus would fall back to FS. > I know it could be violating some specs, however, on embedded systems, it seems make sense to only support HS, since you know there are specific HS USB devices that will connect to your USB system. > One other alternative is that there is at least one EHCI controller > (from ARC/TD) that has the capability to send at FS/LS without a > companion controller. If your hardware uses that, you can handle > HS/FS/LS through just the EHCI controller. You might have to modify > the ehci driver in that case. > Our hardware do not have TT support, we may in the future. Thanks, Julie. This email and any attachments are intended for the sole use of the named recipient(s) and contain(s) confidential information that may be proprietary, privileged or copyrighted under applicable law. If you are not the intended recipient, do not read, copy, or forward this email message or any attachments. Delete this email message and any attachments immediately. -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
