linux-kernel - Re: [PATCH v2 0/2] USB: Quiesce interrupts across pm freeze

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Date:   Tue, 19 Apr 2022 13:49:14 -0400
From:   Alan Stern <stern@...land.harvard.edu>
To:     Oliver Neukum <oneukum@...e.com>
Cc:     Evan Green <evgreen@...omium.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Mathias Nyman <mathias.nyman@...el.com>,
        Rajat Jain <rajatja@...omium.org>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        "Rafael J. Wysocki" <rafael.j.wysocki@...el.com>,
        Razvan Heghedus <heghedus.razvan@...il.com>,
        Wei Ming Chen <jj251510319013@...il.com>,
        Youngjin Jang <yj84.jang@...sung.com>,
        linux-kernel@...r.kernel.org, linux-usb@...r.kernel.org
Subject: Re: [PATCH v2 0/2] USB: Quiesce interrupts across pm freeze

On Tue, Apr 19, 2022 at 05:51:38PM +0200, Oliver Neukum wrote:
> 
> 
> On 19.04.22 16:35, Alan Stern wrote:
> > On Tue, Apr 19, 2022 at 09:05:53AM +0200, Oliver Neukum wrote:
> >
> >
> > We have a set of quirky devices that need HID_QUIRK_ALWAYS_POLL.
> > They have the nasty firmware bug that, if you suspend them without
> > remote wakeup, they will crash or reset themselves.
> > I am afraid that has an obvious relevance to your cool patches.
> > I am not completely sure how to deal with this. It seems to me that the
> > quirk will need to be shifted from HID to core USB and thaw() needs to
> > be translated into usb_device_reset() + reset_resume() for them,
> > but I am not really sure about the optimal mechanism.
> > We may not need to do anything.  This patch specifically addresses 
> > hibernation, not system suspend or runtime suspend.  A device crashing 
> > or resetting during hibernation is not at all unusual; we should be able 
> > to handle such cases properly.
> >
> > The THAW part of suspend-to-hibernation is used only for writing the 
> > memory image to permanent storage.  I doubt that a malfunctioning HID 
> > device would interfere with this process.
> >
> True, if and only if all goes well. At the time thaw() has run writing
> the image to disk can still fail. In that case the devices will still
> be needed.

Consider adding a mechanism to usbcore which would allow an interface 
driver to request that the next time its device is resumed, the core 
should perform a reset-resume.  Would that help?

Alan Stern