On Wed, 8 Nov 2017, Ivid Suvarna wrote: > On Tue, Nov 7, 2017 at 9:19 PM, Alan Stern <st...@rowland.harvard.edu> wrote: > > On Tue, 7 Nov 2017, Ivid Suvarna wrote: > > > >> Hi, > >> > >> I am trying to support suspend to disk(hibernate) on Hikey with 4.4 > >> kernel. During suspend, I could see the usb devices getting reset and I > >> can access them properly. Message can be seen as below: > >> > >> usb 1-1: reset high-speed USB device number 2 using dwc2 > >> usb 1-1.2: reset high-speed USB device number 3 using dwc2 > >> usb 1-1.2.4: reset high-speed USB device number 4 using dwc2 > > > > You might start by asking why the devices need to be reset during > > suspend. I can't see any reason for doing this. > > > > Alan Stern > > > > Yes please. Could you explain as to why the usb needs to reset while > suspending?
I cannot explain it. USB devices do not need to be reset during system suspend. Alan Stern > This scenario is also observed in normal suspend to ram. > > And why the USB gets disconnected on resume from hibernation. > I checked the register dump of usb in /sys/kernel/debug and all > registers after resume have zero value. > > But if I run "usb start" from uboot and then resume, I see that usb > gets initialized again and I am able to use USB on resume. > > Thanks, > Ivid
