linux-kernel - Re: [PATCH v3] usb: ohci-platform: fix usb disconnect issue after s4

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Message-ID: <YxDEUnHIMiNr6Xa9@rowland.harvard.edu>
Date:   Thu, 1 Sep 2022 10:40:18 -0400
From:   Alan Stern <stern@...land.harvard.edu>
To:     Yinbo Zhu <zhuyinbo@...ngson.cn>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org,
        Greg Kroah-Hartman <greg@...ah.com>,
        Patchwork Bot <patchwork-bot@...nel.org>
Subject: Re: [PATCH v3] usb: ohci-platform: fix usb disconnect issue after s4

On Thu, Sep 01, 2022 at 09:54:46AM +0800, Yinbo Zhu wrote:
> Avoid retaining bogus hardware states during resume-from-hibernation.
> Previously we had reset the hardware as part of preparing to reinstate
> the snapshot image. But we can do better now with the new PM framework,
> since we know exactly which resume operations are from hibernation.
> 
> According to the commit 'cd1965db054e ("USB: ohci: move ohci_pci_{
> suspend,resume} to ohci-hcd.c")' and commit '6ec4beb5c701 ("USB: new
> flag for resume-from-hibernation")', the flag "hibernated" is for
> resume-from-hibernation and it should be true when usb resume from disk.
> 
> When this flag "hibernated" is set, the drivers will reset the hardware
> to get rid of any existing state and make sure resume from hibernation
> re-enumerates everything for ohci.

The patch title mentions "usb disconnect issue", but the description 
says nothing about it.  Please explain what this disconnect issue is.

Alan Stern