Re: [PATCH] driver core: Ensure proper suspend/resume ordering

From	"Rafael J. Wysocki" <rjw@rjwysocki.net>
Newsgroups	linux.kernel
Subject	Re: [PATCH] driver core: Ensure proper suspend/resume ordering
Date	2015-09-16 02:40 +0200
Message-ID	<q98Vs-5ap-17@gated-at.bofh.it> (permalink)
References	<q8Zp9-7qt-23@gated-at.bofh.it>
Organization	linux.* mail to news gateway

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On Tuesday, September 15, 2015 10:23:07 AM Alan Stern wrote:
> On Tue, 15 Sep 2015, Rafael J. Wysocki wrote:
> 
> > Hi Alan,
> 
> Hi.
> 
> > On Sat, Sep 12, 2015 at 7:40 PM, Alan Stern <stern@rowland.harvard.edu> wrote:
> > > On Sat, 12 Sep 2015, Rafael J. Wysocki wrote:
> > >
> > >> On Friday, September 11, 2015 03:01:14 PM Alan Stern wrote:
> > >
> > >> > There's also an issue about other types of dependencies.  For instance,
> > >> > it's conceivable that device B might be discovered and depend on device
> > >> > A, even before A has been bound to a driver.  (B might be discovered by
> > >> > A's subsystem rather than A's driver.)  In that case, moving A to the
> > >> > end of the list would cause B to come before A even though B depends on
> > >> > A.  Of course, deferred probing already has this problem.
> > >>
> > >> That may actually happen for PCIe ports and devices below them AFAICS.
> > >>
> > >> Devices below PCIe ports are discovered by the PCI subsystem and the PCIe
> > >> ports need not be probed before those devices are probed.
> > >
> > > Is it possible to change this?  Make it so that devices below PCIe
> > > ports are discovered by the port driver rather than by the PCI
> > > subsystem?  Or would that be far too difficult?
> > 
> > I don't think it would be really useful.
> > 
> > PCIe ports are PCI bridges from the resource allocation and basic
> > functionality perspective, so they are handled accordingly.
> > 
> > The PCIe port driver provides additional services (such as PME/hotplug
> > interrupt handling and advanced error reporting) that aren't necessary
> > for probing devices below the ports.
> > 
> > I guess the ordering of PCIe ports probing might be changed to happen
> > at the "right" time, but care needs to be taken in that case too.
> 
> Does suspending a PCIe port do anything significant?  In particular, 
> does it cut off normal communication with anything attached through 
> the port?

No, it doesn't.

> If it does then we better not move the port device to the end of the 
> dpm_list after any descendant devices have been probed.
> 
> > >> > An easy way to check for this sort of thing would be to verify that a
> > >> > device about to be probed doesn't have any children.  This wouldn't
> > >> > catch all the potential dependencies, but it would be a reasonable
> > >> > start.
> > >>
> > >> That would address the PCIe ports issue.
> > >
> > > Well, it would _detect_ the PCIe ports issue.
> > 
> > That's what I meant. :-)
> > 
> > >  It might also detect other things.
> > 
> > Right.
> 
> All right, I'll try writing a test patch to report these things.

OK, thanks!

Rafael

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Thread

[PATCH] driver core: Ensure proper suspend/resume ordering Thierry Reding <thierry.reding@gmail.com> - 2015-09-10 12:20 +0200
  Re: [PATCH] driver core: Ensure proper suspend/resume ordering Grygorii Strashko <grygorii.strashko@ti.com> - 2015-09-10 13:00 +0200
  Re: [PATCH] driver core: Ensure proper suspend/resume ordering "Rafael J. Wysocki" <rjw@rjwysocki.net> - 2015-09-10 23:50 +0200
    Re: [PATCH] driver core: Ensure proper suspend/resume ordering Thierry Reding <thierry.reding@gmail.com> - 2015-09-11 14:10 +0200
      Re: [PATCH] driver core: Ensure proper suspend/resume ordering Alan Stern <stern@rowland.harvard.edu> - 2015-09-11 21:10 +0200
        Re: [PATCH] driver core: Ensure proper suspend/resume ordering "Rafael J. Wysocki" <rjw@rjwysocki.net> - 2015-09-12 00:10 +0200
          Re: [PATCH] driver core: Ensure proper suspend/resume ordering Alan Stern <stern@rowland.harvard.edu> - 2015-09-12 19:50 +0200
            Re: [PATCH] driver core: Ensure proper suspend/resume ordering "Rafael J. Wysocki" <rafael@kernel.org> - 2015-09-15 02:50 +0200
              Re: [PATCH] driver core: Ensure proper suspend/resume ordering Alan Stern <stern@rowland.harvard.edu> - 2015-09-15 16:30 +0200
                Re: [PATCH] driver core: Ensure proper suspend/resume ordering "Rafael J. Wysocki" <rjw@rjwysocki.net> - 2015-09-16 02:40 +0200
          Re: [PATCH] driver core: Ensure proper suspend/resume ordering Grygorii Strashko <grygorii.strashko@ti.com> - 2015-09-16 15:50 +0200
            Re: [PATCH] driver core: Ensure proper suspend/resume ordering Alan Stern <stern@rowland.harvard.edu> - 2015-09-16 21:30 +0200
              Re: [PATCH] driver core: Ensure proper suspend/resume ordering "Rafael J. Wysocki" <rjw@rjwysocki.net> - 2015-09-17 01:40 +0200
                Re: [PATCH] driver core: Ensure proper suspend/resume ordering Grygorii Strashko <grygorii.strashko@ti.com> - 2015-09-17 17:50 +0200
                Re: [PATCH] driver core: Ensure proper suspend/resume ordering "Rafael J. Wysocki" <rafael@kernel.org> - 2015-09-18 02:00 +0200
                Re: [PATCH] driver core: Ensure proper suspend/resume ordering "Rafael J. Wysocki" <rafael@kernel.org> - 2015-09-18 02:10 +0200
        Re: [PATCH] driver core: Ensure proper suspend/resume ordering Thierry Reding <thierry.reding@gmail.com> - 2015-09-15 18:20 +0200
          Re: [PATCH] driver core: Ensure proper suspend/resume ordering Alan Stern <stern@rowland.harvard.edu> - 2015-09-15 21:20 +0200
            Re: [PATCH] driver core: Ensure proper suspend/resume ordering "Rafael J. Wysocki" <rjw@rjwysocki.net> - 2015-09-16 03:10 +0200
              Re: [PATCH] driver core: Ensure proper suspend/resume ordering Grygorii Strashko <grygorii.strashko@ti.com> - 2015-09-16 15:40 +0200
                Re: [PATCH] driver core: Ensure proper suspend/resume ordering Alan Stern <stern@rowland.harvard.edu> - 2015-09-16 19:00 +0200
              Re: [PATCH] driver core: Ensure proper suspend/resume ordering Alan Stern <stern@rowland.harvard.edu> - 2015-09-16 19:10 +0200
            Re: [PATCH] driver core: Ensure proper suspend/resume ordering Thierry Reding <thierry.reding@gmail.com> - 2015-09-16 15:20 +0200
              Re: [PATCH] driver core: Ensure proper suspend/resume ordering Alan Stern <stern@rowland.harvard.edu> - 2015-09-16 21:30 +0200
                Re: [PATCH] driver core: Ensure proper suspend/resume ordering "Rafael J. Wysocki" <rjw@rjwysocki.net> - 2015-09-17 02:00 +0200
                Re: [PATCH] driver core: Ensure proper suspend/resume ordering "Rafael J. Wysocki" <rafael@kernel.org> - 2015-09-17 04:10 +0200
                Re: [PATCH] driver core: Ensure proper suspend/resume ordering Alan Stern <stern@rowland.harvard.edu> - 2015-09-17 19:10 +0200
                Re: [PATCH] driver core: Ensure proper suspend/resume ordering "Rafael J. Wysocki" <rafael@kernel.org> - 2015-09-17 20:50 +0200
                Re: [PATCH] driver core: Ensure proper suspend/resume ordering Alan Stern <stern@rowland.harvard.edu> - 2015-09-17 23:10 +0200
                Re: [PATCH] driver core: Ensure proper suspend/resume ordering "Rafael J. Wysocki" <rafael@kernel.org> - 2015-09-18 02:20 +0200
                Re: [PATCH] driver core: Ensure proper suspend/resume ordering Thierry Reding <thierry.reding@gmail.com> - 2015-09-18 18:00 +0200
                Re: [PATCH] driver core: Ensure proper suspend/resume ordering "Rafael J. Wysocki" <rafael@kernel.org> - 2015-09-19 01:10 +0200
                Re: [PATCH] driver core: Ensure proper suspend/resume ordering Thierry Reding <thierry.reding@gmail.com> - 2015-09-21 11:00 +0200
                Re: [PATCH] driver core: Ensure proper suspend/resume ordering Alan Stern <stern@rowland.harvard.edu> - 2015-09-21 16:40 +0200
                Re: [PATCH] driver core: Ensure proper suspend/resume ordering "Rafael J. Wysocki" <rjw@rjwysocki.net> - 2015-09-22 02:00 +0200
                Re: [PATCH] driver core: Ensure proper suspend/resume ordering Alan Stern <stern@rowland.harvard.edu> - 2015-09-22 03:30 +0200
                Re: [PATCH] driver core: Ensure proper suspend/resume ordering "Rafael J. Wysocki" <rafael@kernel.org> - 2015-09-22 02:40 +0200
                Re: [PATCH] driver core: Ensure proper suspend/resume ordering Tomeu Vizoso <tomeu.vizoso@collabora.com> - 2015-09-17 07:50 +0200
                Re: [PATCH] driver core: Ensure proper suspend/resume ordering "Rafael J. Wysocki" <rafael@kernel.org> - 2015-09-17 20:20 +0200
                Re: [PATCH] driver core: Ensure proper suspend/resume ordering Alan Stern <stern@rowland.harvard.edu> - 2015-09-17 21:30 +0200
      Re: [PATCH] driver core: Ensure proper suspend/resume ordering "Rafael J. Wysocki" <rjw@rjwysocki.net> - 2015-09-12 00:20 +0200
        Re: [PATCH] driver core: Ensure proper suspend/resume ordering Thierry Reding <thierry.reding@gmail.com> - 2015-09-15 18:00 +0200
          Re: [PATCH] driver core: Ensure proper suspend/resume ordering "Rafael J. Wysocki" <rjw@rjwysocki.net> - 2015-09-16 03:00 +0200
            Re: [PATCH] driver core: Ensure proper suspend/resume ordering Grygorii Strashko <grygorii.strashko@ti.com> - 2015-09-16 15:40 +0200
              Re: [PATCH] driver core: Ensure proper suspend/resume ordering "Rafael J. Wysocki" <rjw@rjwysocki.net> - 2015-09-17 02:30 +0200
    Re: [PATCH] driver core: Ensure proper suspend/resume ordering Alan Stern <stern@rowland.harvard.edu> - 2015-09-11 16:10 +0200

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