linux-kernel - Re: Suspend to disk with usb connected fails to detect usb(reset) during resume

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <Pine.LNX.4.44L0.1711081039300.1481-100000@iolanthe.rowland.org>
Date:   Wed, 8 Nov 2017 10:42:25 -0500 (EST)
From:   Alan Stern <stern@...land.harvard.edu>
To:     Ivid Suvarna <ivid.suvarna@...il.com>
cc:     USB list <linux-usb@...r.kernel.org>, <balbi@...nel.org>,
        <gregkh@...uxfoundation.org>, Billy Araujo <billyaraujo@...il.com>,
        <johnyoun@...opsys.com>, <dinguyen@...nel.org>,
        Felipe Balbi <felipe.balbi@...ux.intel.com>,
        Kernel development list <linux-kernel@...r.kernel.org>,
        Laurent Pinchart <laurent.pinchart@...asonboard.com>,
        Oliver Neukum <oneukum@...e.com>,
        Johan Hovold <johan@...nel.org>,
        Michal Nazarewicz <mina86@...a86.com>,
        Vincent Pelletier <plr.vincent@...il.com>,
        Jerry Zhang <zhangjerry@...gle.com>,
        John Keeping <john@...anate.com>,
        Krzysztof Opasiak <k.opasiak@...sung.com>,
        Abdulhadi Mohamed <abdulahhadi2@...il.com>,
        Matthew Wilcox <willy@...ux.intel.com>,
        Janusz Dziedzic <januszx.dziedzic@...ux.intel.com>
Subject: Re: Suspend to disk with usb connected fails to detect usb(reset)
 during resume

On Wed, 8 Nov 2017, Ivid Suvarna wrote:

> On Tue, Nov 7, 2017 at 9:19 PM, Alan Stern <stern@...land.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