On Mon, 12 Oct 2009, Yang Fei-AFY095 wrote: > >> I'm still not sure how to interprete the comment "High-speed root > hubs > >> are an exception; they need to resume whenever the system wakes up in > > >> order for USB-PERSIST port handover to work properly". What is broken > > >> if we set skip_sys_resume regardless of the speed? > > >Then USB-PERSIST port handover won't work. If a full-speed device is > attached to the computer, and the UHCI or OHCI host > >controller gets reset or loses power during a system suspend, then > during resume the kernel will believe that the device was >unplugged and > then replugged. > >If the device was a USB drive and it contained a mounted filesystem > then the filesystem will become unusable. > > In the system that I'm currently working on, resuming EHCI whenever > system wakes up is causing quite a bit current drain, which we are > fighting to optimize. If we have only one high speed device connected to > the EHCI through TLL interface (no transceiver or PHY in between), then > it would be fine to skip system resume, right? Please advise. If no devices are plugged in to a companion controller then it is okay to leave the EHCI controller suspended during a system resume. Alan Stern -- 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
