Re: [PATCH v3] usb: vhci-hcd: Prevent suspending virtually attached devices

[Shuah Khan]

On 9/24/25 11:01, Cristian Ciocaltea wrote:
> Hi,
>
> On 9/2/25 3:15 PM, Cristian Ciocaltea wrote:
> > The VHCI platform driver aims to forbid entering system suspend when at
> > least one of the virtual USB ports are bound to an active USB/IP
> > connection.
> >
> > However, in some cases, the detection logic doesn't work reliably, i.e.
> > when all devices attached to the virtual root hub have been already
> > suspended, leading to a broken suspend state, with unrecoverable resume.
> >
> > Ensure the virtually attached devices do not enter suspend by setting
> > the syscore PM flag.  Note this is currently limited to the client side
> > only, since the server side doesn't implement system suspend prevention.
> >
> > Fixes: 04679b3489e0 ("Staging: USB/IP: add client driver")
> > Signed-off-by: Cristian Ciocaltea <cristian.ciocaltea@xxxxxxxxxxxxx>
> > ---
> > The USB/IP Virtual Host Controller (VHCI) platform driver is expected to
> > prevent entering system suspend when at least one remote device is
> > attached to the virtual USB root hub.
> >
> > However, in some cases, the detection logic for active USB/IP
> > connections doesn't seem to work reliably, e.g. when all devices
> > attached to the virtual hub have been already suspended.  This will
> > normally lead to a broken suspend state, with unrecoverable resume.
> >
> > The first patch of the series provides a workaround to ensure the
> > virtually attached devices do not enter suspend.  Note this is currently
> > limited to the client side (vhci_hcd) only, since the server side
> > (usbip_host) doesn't implement system suspend prevention.
> >
> > IMPORTANT:
> >
> > Please note commit aa7a9275ab81 ("PM: sleep: Suspend async parents after
> > suspending children") from v6.16-rc1 introduced a regression which
> > breaks the suspend cancellation and hangs the system.
> >
> > A fix [1] has been already provided, which also landed soon after in
> > v6.16-rc7 under commit ebd6884167ea ("PM: sleep: Update power.completion
> > for all devices on errors").
> >
> > [1] https://lore.kernel.org/all/6191258.lOV4Wx5bFT@xxxxxxxxxxxxx/
> > ---
> > Changes in v3:
> > - Moved all driver cleanup patches to a separate series:
> >    https://lore.kernel.org/all/20250902-vhci-hcd-cleanup-v1-0-1d46247cb234@xxxxxxxxxxxxx/
> > - Replaced FIXME with NOTE in the new comment block, as it refers to a
> >    potential cleanup of redundant code rather than addressing a
> >    functional issue
> > - Rebased remaining patch onto next-20250902
> > - Link to v2: https://lore.kernel.org/r/20250726-vhci-hcd-suspend-fix-v2-0-189266dfdfaa@xxxxxxxxxxxxx
>
> Just a kind reminder in case there's still a chance to get this and/or the
> cleanup patches queued for v6.18.

Sorry for the delay - it has been crazy few weeks for me.

Acked-by: Shuah Khan <skhan@xxxxxxxxxxxxxxxxxxx>

thanks,
-- Shuah