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

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Date:   Tue, 19 Apr 2022 17:51:38 +0200
From:   Oliver Neukum <oneukum@...e.com>
To:     Alan Stern <stern@...land.harvard.edu>,
        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 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.

    Regards
        Oliver