On 11/08/2017 06:29 AM, 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? > 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. >
Registers with zero value is indicative of a clock not getting turned on, at least that I have encountered with DWC2 on the SoCFPGA platform. Dinh
