Re: [PATCH v2 02/10] driver core: Functional dependencies tracking support

Re: [PATCH v2 02/10] driver core: Functional dependencies tracking support

[Lukas Wunner]

On Fri, Jun 17, 2016 at 02:54:56PM +0200, Rafael J. Wysocki wrote:
> On Fri, Jun 17, 2016 at 12:36 PM, Lukas Wunner <lukas@wunner.de> wrote:
> > On Fri, Jun 17, 2016 at 08:26:52AM +0200, Marek Szyprowski wrote:
> > > From: "Rafael J. Wysocki" <rafael.j.wysocki@intel.com>
> > We also have such a functional dependency for Thunderbolt on Macs:
> > On resume from system sleep, the PCIe hotplug ports may not resume
> > before the thunderbolt driver has reestablished the PCI tunnels.
> > Currently this is enforced by quirk_apple_wait_for_thunderbolt()
> > in drivers/pci/quirks.c. It would be good if we could represent
> > this dependency using something like Rafael's approach instead of
> > open coding it, however one detail in Rafael's patches is problematic:
> >
> > > New links are added by calling device_link_add() which may happen
> > > either before the consumer device is probed or when probing it, in
> > > which case the caller needs to ensure that the driver of the
> > > supplier device is present and functional and the DEVICE_LINK_PROBE_TIME
> > > flag should be passed to device_link_add() to reflect that.
> >
> > The thunderbolt driver cannot call device_link_add() before the
> > PCIe hotplug ports are bound to a driver unless we amend portdrv
> > to return -EPROBE_DEFER for Thunderbolt hotplug ports on Macs
> > if the thunderbolt driver isn't loaded.
> >
> > It would therefore be beneficial if device_link_add() can be
> > called even *after* the consumer is bound.
> 
> I don't quite follow.
> 
> Who's the provider and who's the consumer here?

thunderbolt.ko is the supplier. The PCIe hotplug ports of Thunderbolt
host controllers are the consumers.

If thunderbolt.ko is not loaded, no special precautions are needed for
the hotplug ports.

However *if* it is loaded and the system is suspended and there are
Thunderbolt devices plugged in, then on resume the hotplug ports must
wait for thunderbolt.ko to reestablish the PCI tunnels. If they do not
wait, things will go south because when pci_pm_resume_noirq() is called
for the devices *below* the hotplug port, we will try to put them into D0
(via pci_pm_default_resume_early()) and call pci_restore_state() even
though those hotplugged devices are not yet reachable.

So what I'd like to do is call device_link_add() when thunderbolt.ko
is loaded to shove a dependency onto the hotplug ports. But the hotplug
ports will long since have been bound at that point (to portdrv).
So it should be allowed to call device_link_add() ex post facto, after
the consumer has been bound.

Let me know if I still failed to convey the problem in an intelligible
way.

I had a similar problem with the Runtime PM for Thunderbolt series
(which BTW is still awaiting reviews):
http://www.spinics.net/lists/linux-pci/msg51158.html

The PM core allows calls to dev_pm_domain_set() only during ->probe or
if the device is unbound. Same constraint as with device_link_add().
This constraint was a major obstacle for me and I had to jump through
numerous additional hoops to work around it:

Thunderbolt controllers on Macs can be put into D3cold, but not with
standard ACPI methods, so platform_pci_power_manageable() is false for
these devices. Now this nothing unusual, the same applies to dual GPU
laptops (custom ACPI DSMs for Nvidia Optimus and AMD PowerXpress).

For such discrete GPUs, a struct dev_pm_domain is set during ->probe
(drivers/gpu/vga/vga_switcheroo.c: vga_switcheroo_init_domain_pm_ops()).
But I can't do that for Thunderbolt because the device in question is
a PCIe upstream port. Ideally I would shove a dev_pm_domain on the
upstream port when thunderbolt.ko loads, but again at that point
the port has long since been bound (to portdrv) so I can't call
dev_pm_domain_set().

The workaround I settled on is to attach to the upstream port as a
service driver, call down to the service driver's ->runtime_suspend
hooks when the port runtime suspends and power the controller down.
In addition, I had to make sure that saved_state isn't clobbered on
resume (patch [09/13]).

It would be good if someone who has a bird's eye view of the PM core
(i.e., you) could make a decision
(1) if it's possible and worthwhile to allow dev_pm_domain_set() for
    already bound devices, and
(2) if the PCI core should be be able to deal with devices which are
    runtime suspended to D3cold but not by the platform (because that's
    what patch [09/13] does).

If the answer to (2) is yes then there's some more stuff to fix:
Discrete GPUs on dual GPU laptops can be manually suspended to D3cold
behind the PM core's back by loading nouveau / radeon / amdgpu with
runpm=0 and writing OFF to the vga_switcheroo debugfs interface.
This is currently broken in conjunction with system sleep (the GPU
is no longer accessible after resume) because pci_pm_resume_noirq()
calls pci_restore_state() even though the device is in D3cold and not
power-manageable by the platform.

Thanks,

Lukas

Re: [PATCH v2 02/10] driver core: Functional dependencies tracking support

[Rafael J. Wysocki]

On Friday, June 17, 2016 04:07:38 PM Lukas Wunner wrote:
> On Fri, Jun 17, 2016 at 02:54:56PM +0200, Rafael J. Wysocki wrote:
> > On Fri, Jun 17, 2016 at 12:36 PM, Lukas Wunner <lukas@wunner.de> wrote:
> > > On Fri, Jun 17, 2016 at 08:26:52AM +0200, Marek Szyprowski wrote:
> > > > From: "Rafael J. Wysocki" <rafael.j.wysocki@intel.com>
> > > We also have such a functional dependency for Thunderbolt on Macs:
> > > On resume from system sleep, the PCIe hotplug ports may not resume
> > > before the thunderbolt driver has reestablished the PCI tunnels.
> > > Currently this is enforced by quirk_apple_wait_for_thunderbolt()
> > > in drivers/pci/quirks.c. It would be good if we could represent
> > > this dependency using something like Rafael's approach instead of
> > > open coding it, however one detail in Rafael's patches is problematic:
> > >
> > > > New links are added by calling device_link_add() which may happen
> > > > either before the consumer device is probed or when probing it, in
> > > > which case the caller needs to ensure that the driver of the
> > > > supplier device is present and functional and the DEVICE_LINK_PROBE_TIME
> > > > flag should be passed to device_link_add() to reflect that.
> > >
> > > The thunderbolt driver cannot call device_link_add() before the
> > > PCIe hotplug ports are bound to a driver unless we amend portdrv
> > > to return -EPROBE_DEFER for Thunderbolt hotplug ports on Macs
> > > if the thunderbolt driver isn't loaded.
> > >
> > > It would therefore be beneficial if device_link_add() can be
> > > called even *after* the consumer is bound.
> > 
> > I don't quite follow.
> > 
> > Who's the provider and who's the consumer here?
> 
> thunderbolt.ko is the supplier.

But it binds to the children of the ports that are supposed to be its
consumers?

Why is that even expected to work?

Thanks,
Rafael


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Re: [PATCH v2 02/10] driver core: Functional dependencies tracking support

[Lukas Wunner]

On Wed, Jul 20, 2016 at 02:33:18AM +0200, Rafael J. Wysocki wrote:
> On Friday, June 17, 2016 04:07:38 PM Lukas Wunner wrote:
> > On Fri, Jun 17, 2016 at 02:54:56PM +0200, Rafael J. Wysocki wrote:
> > > On Fri, Jun 17, 2016 at 12:36 PM, Lukas Wunner <lukas@wunner.de> wrote:
> > > > On Fri, Jun 17, 2016 at 08:26:52AM +0200, Marek Szyprowski wrote:
> > > > > From: "Rafael J. Wysocki" <rafael.j.wysocki@intel.com>
> > > > We also have such a functional dependency for Thunderbolt on Macs:
> > > > On resume from system sleep, the PCIe hotplug ports may not resume
> > > > before the thunderbolt driver has reestablished the PCI tunnels.
> > > > Currently this is enforced by quirk_apple_wait_for_thunderbolt()
> > > > in drivers/pci/quirks.c. It would be good if we could represent
> > > > this dependency using something like Rafael's approach instead of
> > > > open coding it, however one detail in Rafael's patches is problematic:
> > > >
> > > > > New links are added by calling device_link_add() which may happen
> > > > > either before the consumer device is probed or when probing it, in
> > > > > which case the caller needs to ensure that the driver of the
> > > > > supplier device is present and functional and the DEVICE_LINK_PROBE_TIME
> > > > > flag should be passed to device_link_add() to reflect that.
> > > >
> > > > The thunderbolt driver cannot call device_link_add() before the
> > > > PCIe hotplug ports are bound to a driver unless we amend portdrv
> > > > to return -EPROBE_DEFER for Thunderbolt hotplug ports on Macs
> > > > if the thunderbolt driver isn't loaded.
> > > >
> > > > It would therefore be beneficial if device_link_add() can be
> > > > called even *after* the consumer is bound.
> > > 
> > > I don't quite follow.
> > > 
> > > Who's the provider and who's the consumer here?
> > 
> > thunderbolt.ko is the supplier.
> 
> But it binds to the children of the ports that are supposed to be its
> consumers?
> 
> Why is that even expected to work?

No, the consumers are aunts (or uncles) of the supplier, if you will. :-)

The consumers are the hotplug ports (named "Downstream Bridge 1 / 2" in
the drawing below). The supplier is the NHI:

      (Root Port) ---- Upstream Bridge --+-- Downstream Bridge 0 ---- NHI
                                         +-- Downstream Bridge 1 --
                                         +-- Downstream Bridge 2 --
                                         ...

We're calling pci_power_up() and pci_restore_state() from
pci_pm_resume_noirq(). And that will fail for devices below
the hotplug ports if the PCI tunnels haven't been re-established
yet by the NHI.

Currently we achieve that via quirk_apple_wait_for_thunderbolt() in
drivers/pci/quirks.c. It would be more elegant if we could make this
relationship explicit with "device links" and let the core handle it.

Or am I mistaken and this particular use case is not what "device links"
are intended for?

Thanks,

Lukas

Re: [PATCH v2 02/10] driver core: Functional dependencies tracking support

[Rafael J. Wysocki]

On Wednesday, July 20, 2016 08:24:50 AM Lukas Wunner wrote:
> On Wed, Jul 20, 2016 at 02:33:18AM +0200, Rafael J. Wysocki wrote:
> > On Friday, June 17, 2016 04:07:38 PM Lukas Wunner wrote:
> > > On Fri, Jun 17, 2016 at 02:54:56PM +0200, Rafael J. Wysocki wrote:
> > > > On Fri, Jun 17, 2016 at 12:36 PM, Lukas Wunner <lukas@wunner.de> wrote:
> > > > > On Fri, Jun 17, 2016 at 08:26:52AM +0200, Marek Szyprowski wrote:
> > > > > > From: "Rafael J. Wysocki" <rafael.j.wysocki@intel.com>
> > > > > We also have such a functional dependency for Thunderbolt on Macs:
> > > > > On resume from system sleep, the PCIe hotplug ports may not resume
> > > > > before the thunderbolt driver has reestablished the PCI tunnels.
> > > > > Currently this is enforced by quirk_apple_wait_for_thunderbolt()
> > > > > in drivers/pci/quirks.c. It would be good if we could represent
> > > > > this dependency using something like Rafael's approach instead of
> > > > > open coding it, however one detail in Rafael's patches is problematic:
> > > > >
> > > > > > New links are added by calling device_link_add() which may happen
> > > > > > either before the consumer device is probed or when probing it, in
> > > > > > which case the caller needs to ensure that the driver of the
> > > > > > supplier device is present and functional and the DEVICE_LINK_PROBE_TIME
> > > > > > flag should be passed to device_link_add() to reflect that.
> > > > >
> > > > > The thunderbolt driver cannot call device_link_add() before the
> > > > > PCIe hotplug ports are bound to a driver unless we amend portdrv
> > > > > to return -EPROBE_DEFER for Thunderbolt hotplug ports on Macs
> > > > > if the thunderbolt driver isn't loaded.
> > > > >
> > > > > It would therefore be beneficial if device_link_add() can be
> > > > > called even *after* the consumer is bound.
> > > > 
> > > > I don't quite follow.
> > > > 
> > > > Who's the provider and who's the consumer here?
> > > 
> > > thunderbolt.ko is the supplier.
> > 
> > But it binds to the children of the ports that are supposed to be its
> > consumers?
> > 
> > Why is that even expected to work?
> 
> No, the consumers are aunts (or uncles) of the supplier, if you will. :-)
> 
> The consumers are the hotplug ports (named "Downstream Bridge 1 / 2" in
> the drawing below). The supplier is the NHI:
> 
>       (Root Port) ---- Upstream Bridge --+-- Downstream Bridge 0 ---- NHI
>                                          +-- Downstream Bridge 1 --
>                                          +-- Downstream Bridge 2 --
>                                          ...
> 
> We're calling pci_power_up() and pci_restore_state() from
> pci_pm_resume_noirq(). And that will fail for devices below
> the hotplug ports if the PCI tunnels haven't been re-established
> yet by the NHI.

So the NHI is a PCIe device, right?

Does the Thunderbolt driver bind to that device?

> Currently we achieve that via quirk_apple_wait_for_thunderbolt() in
> drivers/pci/quirks.c. It would be more elegant if we could make this
> relationship explicit with "device links" and let the core handle it.
> 
> Or am I mistaken and this particular use case is not what "device links"
> are intended for?

I'm not sure yet.

Thanks,
Rafael


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Re: [PATCH v2 02/10] driver core: Functional dependencies tracking support

[Lukas Wunner]

On Wed, Jul 20, 2016 at 02:52:42PM +0200, Rafael J. Wysocki wrote:
> On Wednesday, July 20, 2016 08:24:50 AM Lukas Wunner wrote:
> > On Wed, Jul 20, 2016 at 02:33:18AM +0200, Rafael J. Wysocki wrote:
> > > On Friday, June 17, 2016 04:07:38 PM Lukas Wunner wrote:
> > > > On Fri, Jun 17, 2016 at 02:54:56PM +0200, Rafael J. Wysocki wrote:
> > > > > On Fri, Jun 17, 2016 at 12:36 PM, Lukas Wunner <lukas@wunner.de> wrote:
> > > > > > On Fri, Jun 17, 2016 at 08:26:52AM +0200, Marek Szyprowski wrote:
> > > > > > > From: "Rafael J. Wysocki" <rafael.j.wysocki@intel.com>
> > > > > > We also have such a functional dependency for Thunderbolt on Macs:
> > > > > > On resume from system sleep, the PCIe hotplug ports may not resume
> > > > > > before the thunderbolt driver has reestablished the PCI tunnels.
> > > > > > Currently this is enforced by quirk_apple_wait_for_thunderbolt()
> > > > > > in drivers/pci/quirks.c. It would be good if we could represent
> > > > > > this dependency using something like Rafael's approach instead of
> > > > > > open coding it, however one detail in Rafael's patches is problematic:
> > > > > >
> > > > > > > New links are added by calling device_link_add() which may happen
> > > > > > > either before the consumer device is probed or when probing it, in
> > > > > > > which case the caller needs to ensure that the driver of the
> > > > > > > supplier device is present and functional and the DEVICE_LINK_PROBE_TIME
> > > > > > > flag should be passed to device_link_add() to reflect that.
> > > > > >
> > > > > > The thunderbolt driver cannot call device_link_add() before the
> > > > > > PCIe hotplug ports are bound to a driver unless we amend portdrv
> > > > > > to return -EPROBE_DEFER for Thunderbolt hotplug ports on Macs
> > > > > > if the thunderbolt driver isn't loaded.
> > > > > >
> > > > > > It would therefore be beneficial if device_link_add() can be
> > > > > > called even *after* the consumer is bound.
> > > > > 
> > > > > I don't quite follow.
> > > > > 
> > > > > Who's the provider and who's the consumer here?
> > > > 
> > > > thunderbolt.ko is the supplier.
> > > 
> > > But it binds to the children of the ports that are supposed to be its
> > > consumers?
> > > 
> > > Why is that even expected to work?
> > 
> > No, the consumers are aunts (or uncles) of the supplier, if you will. :-)
> > 
> > The consumers are the hotplug ports (named "Downstream Bridge 1 / 2" in
> > the drawing below). The supplier is the NHI:
> > 
> >       (Root Port) ---- Upstream Bridge --+-- Downstream Bridge 0 ---- NHI
> >                                          +-- Downstream Bridge 1 --
> >                                          +-- Downstream Bridge 2 --
> >                                          ...
> > 
> > We're calling pci_power_up() and pci_restore_state() from
> > pci_pm_resume_noirq(). And that will fail for devices below
> > the hotplug ports if the PCI tunnels haven't been re-established
> > yet by the NHI.
> 
> So the NHI is a PCIe device, right?
> 
> Does the Thunderbolt driver bind to that device?

The NHI is a PCI device but not a bridge. It has class 0x88000.
Yes, thunderbolt.ko binds to the NHI.

And portdrv binds to the upstream bridge and downstream bridges.
Those have class 0x60400.

Best regards,

Lukas

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Re: [PATCH v2 02/10] driver core: Functional dependencies tracking support

[Rafael J. Wysocki]

On Wednesday, July 20, 2016 05:23:40 PM Lukas Wunner wrote:
> On Wed, Jul 20, 2016 at 02:52:42PM +0200, Rafael J. Wysocki wrote:
> > On Wednesday, July 20, 2016 08:24:50 AM Lukas Wunner wrote:
> > > On Wed, Jul 20, 2016 at 02:33:18AM +0200, Rafael J. Wysocki wrote:
> > > > On Friday, June 17, 2016 04:07:38 PM Lukas Wunner wrote:
> > > > > On Fri, Jun 17, 2016 at 02:54:56PM +0200, Rafael J. Wysocki wrote:
> > > > > > On Fri, Jun 17, 2016 at 12:36 PM, Lukas Wunner <lukas@wunner.de> wrote:
> > > > > > > On Fri, Jun 17, 2016 at 08:26:52AM +0200, Marek Szyprowski wrote:
> > > > > > > > From: "Rafael J. Wysocki" <rafael.j.wysocki@intel.com>
> > > > > > > We also have such a functional dependency for Thunderbolt on Macs:
> > > > > > > On resume from system sleep, the PCIe hotplug ports may not resume
> > > > > > > before the thunderbolt driver has reestablished the PCI tunnels.
> > > > > > > Currently this is enforced by quirk_apple_wait_for_thunderbolt()
> > > > > > > in drivers/pci/quirks.c. It would be good if we could represent
> > > > > > > this dependency using something like Rafael's approach instead of
> > > > > > > open coding it, however one detail in Rafael's patches is problematic:
> > > > > > >
> > > > > > > > New links are added by calling device_link_add() which may happen
> > > > > > > > either before the consumer device is probed or when probing it, in
> > > > > > > > which case the caller needs to ensure that the driver of the
> > > > > > > > supplier device is present and functional and the DEVICE_LINK_PROBE_TIME
> > > > > > > > flag should be passed to device_link_add() to reflect that.
> > > > > > >
> > > > > > > The thunderbolt driver cannot call device_link_add() before the
> > > > > > > PCIe hotplug ports are bound to a driver unless we amend portdrv
> > > > > > > to return -EPROBE_DEFER for Thunderbolt hotplug ports on Macs
> > > > > > > if the thunderbolt driver isn't loaded.
> > > > > > >
> > > > > > > It would therefore be beneficial if device_link_add() can be
> > > > > > > called even *after* the consumer is bound.
> > > > > > 
> > > > > > I don't quite follow.
> > > > > > 
> > > > > > Who's the provider and who's the consumer here?
> > > > > 
> > > > > thunderbolt.ko is the supplier.
> > > > 
> > > > But it binds to the children of the ports that are supposed to be its
> > > > consumers?
> > > > 
> > > > Why is that even expected to work?
> > > 
> > > No, the consumers are aunts (or uncles) of the supplier, if you will. :-)
> > > 
> > > The consumers are the hotplug ports (named "Downstream Bridge 1 / 2" in
> > > the drawing below). The supplier is the NHI:
> > > 
> > >       (Root Port) ---- Upstream Bridge --+-- Downstream Bridge 0 ---- NHI
> > >                                          +-- Downstream Bridge 1 --
> > >                                          +-- Downstream Bridge 2 --
> > >                                          ...
> > > 
> > > We're calling pci_power_up() and pci_restore_state() from
> > > pci_pm_resume_noirq(). And that will fail for devices below
> > > the hotplug ports if the PCI tunnels haven't been re-established
> > > yet by the NHI.
> > 
> > So the NHI is a PCIe device, right?
> > 
> > Does the Thunderbolt driver bind to that device?
> 
> The NHI is a PCI device but not a bridge. It has class 0x88000.
> Yes, thunderbolt.ko binds to the NHI.
> 
> And portdrv binds to the upstream bridge and downstream bridges.
> Those have class 0x60400.

OK, so why would there be a problem with creating links from the NHI (producer)
to the ports (consumers) before binding portdrv to them?

Thanks,
Rafael


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Re: [PATCH v2 02/10] driver core: Functional dependencies tracking support

[Lukas Wunner]

On Thu, Jul 21, 2016 at 12:51:31AM +0200, Rafael J. Wysocki wrote:
> On Wednesday, July 20, 2016 05:23:40 PM Lukas Wunner wrote:
> > On Wed, Jul 20, 2016 at 02:52:42PM +0200, Rafael J. Wysocki wrote:
> > > On Wednesday, July 20, 2016 08:24:50 AM Lukas Wunner wrote:
> > > > On Wed, Jul 20, 2016 at 02:33:18AM +0200, Rafael J. Wysocki wrote:
> > > > > On Friday, June 17, 2016 04:07:38 PM Lukas Wunner wrote:
> > > > > > On Fri, Jun 17, 2016 at 02:54:56PM +0200, Rafael J. Wysocki wrote:
> > > > > > > On Fri, Jun 17, 2016 at 12:36 PM, Lukas Wunner <lukas@wunner.de> wrote:
> > > > > > > > On Fri, Jun 17, 2016 at 08:26:52AM +0200, Marek Szyprowski wrote:
> > > > > > > > > From: "Rafael J. Wysocki" <rafael.j.wysocki@intel.com>
> > > > > > > > We also have such a functional dependency for Thunderbolt on Macs:
> > > > > > > > On resume from system sleep, the PCIe hotplug ports may not resume
> > > > > > > > before the thunderbolt driver has reestablished the PCI tunnels.
> > > > > > > > Currently this is enforced by quirk_apple_wait_for_thunderbolt()
> > > > > > > > in drivers/pci/quirks.c. It would be good if we could represent
> > > > > > > > this dependency using something like Rafael's approach instead of
> > > > > > > > open coding it, however one detail in Rafael's patches is problematic:
> > > > > > > >
> > > > > > > > > New links are added by calling device_link_add() which may happen
> > > > > > > > > either before the consumer device is probed or when probing it, in
> > > > > > > > > which case the caller needs to ensure that the driver of the
> > > > > > > > > supplier device is present and functional and the DEVICE_LINK_PROBE_TIME
> > > > > > > > > flag should be passed to device_link_add() to reflect that.
> > > > > > > >
> > > > > > > > The thunderbolt driver cannot call device_link_add() before the
> > > > > > > > PCIe hotplug ports are bound to a driver unless we amend portdrv
> > > > > > > > to return -EPROBE_DEFER for Thunderbolt hotplug ports on Macs
> > > > > > > > if the thunderbolt driver isn't loaded.
> > > > > > > >
> > > > > > > > It would therefore be beneficial if device_link_add() can be
> > > > > > > > called even *after* the consumer is bound.
> > > > > > > 
> > > > > > > I don't quite follow.
> > > > > > > 
> > > > > > > Who's the provider and who's the consumer here?
> > > > > > 
> > > > > > thunderbolt.ko is the supplier.
> > > > > 
> > > > > But it binds to the children of the ports that are supposed to be its
> > > > > consumers?
> > > > > 
> > > > > Why is that even expected to work?
> > > > 
> > > > No, the consumers are aunts (or uncles) of the supplier, if you will. :-)
> > > > 
> > > > The consumers are the hotplug ports (named "Downstream Bridge 1 / 2" in
> > > > the drawing below). The supplier is the NHI:
> > > > 
> > > >       (Root Port) ---- Upstream Bridge --+-- Downstream Bridge 0 ---- NHI
> > > >                                          +-- Downstream Bridge 1 --
> > > >                                          +-- Downstream Bridge 2 --
> > > >                                          ...
> > > > 
> > > > We're calling pci_power_up() and pci_restore_state() from
> > > > pci_pm_resume_noirq(). And that will fail for devices below
> > > > the hotplug ports if the PCI tunnels haven't been re-established
> > > > yet by the NHI.
> > > 
> > > So the NHI is a PCIe device, right?
> > > 
> > > Does the Thunderbolt driver bind to that device?
> > 
> > The NHI is a PCI device but not a bridge. It has class 0x88000.
> > Yes, thunderbolt.ko binds to the NHI.
> > 
> > And portdrv binds to the upstream bridge and downstream bridges.
> > Those have class 0x60400.
> 
> OK, so why would there be a problem with creating links from the NHI
> (producer) to the ports (consumers) before binding portdrv to them?

Because the ordering in which drivers bind isn't guaranteed. At least
on my machine (Debian), portdrv always binds before thunderbolt.

I guess I could amend portdrv to return -EPROBE_DEFER on Macs if
no driver is bound to the NHI. Doesn't feel pretty to me though.

Ultimately this seems to be the same issue as with calling
dev_pm_domain_set() for a bound device. Perhaps device_link_add()
can likewise be allowed if a runtime PM ref is held for the devices
and the call happens under lock_system_sleep()?

Thanks,

Lukas

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Re: [PATCH v2 02/10] driver core: Functional dependencies tracking support

[Rafael J. Wysocki]

On Thursday, July 21, 2016 01:25:53 AM Lukas Wunner wrote:
> On Thu, Jul 21, 2016 at 12:51:31AM +0200, Rafael J. Wysocki wrote:
> > On Wednesday, July 20, 2016 05:23:40 PM Lukas Wunner wrote:
> > > On Wed, Jul 20, 2016 at 02:52:42PM +0200, Rafael J. Wysocki wrote:
> > > > On Wednesday, July 20, 2016 08:24:50 AM Lukas Wunner wrote:
> > > > > On Wed, Jul 20, 2016 at 02:33:18AM +0200, Rafael J. Wysocki wrote:
> > > > > > On Friday, June 17, 2016 04:07:38 PM Lukas Wunner wrote:
> > > > > > > On Fri, Jun 17, 2016 at 02:54:56PM +0200, Rafael J. Wysocki wrote:
> > > > > > > > On Fri, Jun 17, 2016 at 12:36 PM, Lukas Wunner <lukas@wunner.de> wrote:
> > > > > > > > > On Fri, Jun 17, 2016 at 08:26:52AM +0200, Marek Szyprowski wrote:
> > > > > > > > > > From: "Rafael J. Wysocki" <rafael.j.wysocki@intel.com>
> > > > > > > > > We also have such a functional dependency for Thunderbolt on Macs:
> > > > > > > > > On resume from system sleep, the PCIe hotplug ports may not resume
> > > > > > > > > before the thunderbolt driver has reestablished the PCI tunnels.
> > > > > > > > > Currently this is enforced by quirk_apple_wait_for_thunderbolt()
> > > > > > > > > in drivers/pci/quirks.c. It would be good if we could represent
> > > > > > > > > this dependency using something like Rafael's approach instead of
> > > > > > > > > open coding it, however one detail in Rafael's patches is problematic:
> > > > > > > > >
> > > > > > > > > > New links are added by calling device_link_add() which may happen
> > > > > > > > > > either before the consumer device is probed or when probing it, in
> > > > > > > > > > which case the caller needs to ensure that the driver of the
> > > > > > > > > > supplier device is present and functional and the DEVICE_LINK_PROBE_TIME
> > > > > > > > > > flag should be passed to device_link_add() to reflect that.
> > > > > > > > >
> > > > > > > > > The thunderbolt driver cannot call device_link_add() before the
> > > > > > > > > PCIe hotplug ports are bound to a driver unless we amend portdrv
> > > > > > > > > to return -EPROBE_DEFER for Thunderbolt hotplug ports on Macs
> > > > > > > > > if the thunderbolt driver isn't loaded.
> > > > > > > > >
> > > > > > > > > It would therefore be beneficial if device_link_add() can be
> > > > > > > > > called even *after* the consumer is bound.
> > > > > > > > 
> > > > > > > > I don't quite follow.
> > > > > > > > 
> > > > > > > > Who's the provider and who's the consumer here?
> > > > > > > 
> > > > > > > thunderbolt.ko is the supplier.
> > > > > > 
> > > > > > But it binds to the children of the ports that are supposed to be its
> > > > > > consumers?
> > > > > > 
> > > > > > Why is that even expected to work?
> > > > > 
> > > > > No, the consumers are aunts (or uncles) of the supplier, if you will. :-)
> > > > > 
> > > > > The consumers are the hotplug ports (named "Downstream Bridge 1 / 2" in
> > > > > the drawing below). The supplier is the NHI:
> > > > > 
> > > > >       (Root Port) ---- Upstream Bridge --+-- Downstream Bridge 0 ---- NHI
> > > > >                                          +-- Downstream Bridge 1 --
> > > > >                                          +-- Downstream Bridge 2 --
> > > > >                                          ...
> > > > > 
> > > > > We're calling pci_power_up() and pci_restore_state() from
> > > > > pci_pm_resume_noirq(). And that will fail for devices below
> > > > > the hotplug ports if the PCI tunnels haven't been re-established
> > > > > yet by the NHI.
> > > > 
> > > > So the NHI is a PCIe device, right?
> > > > 
> > > > Does the Thunderbolt driver bind to that device?
> > > 
> > > The NHI is a PCI device but not a bridge. It has class 0x88000.
> > > Yes, thunderbolt.ko binds to the NHI.
> > > 
> > > And portdrv binds to the upstream bridge and downstream bridges.
> > > Those have class 0x60400.
> > 
> > OK, so why would there be a problem with creating links from the NHI
> > (producer) to the ports (consumers) before binding portdrv to them?
> 
> Because the ordering in which drivers bind isn't guaranteed. At least
> on my machine (Debian), portdrv always binds before thunderbolt.

But what drivers have to do with that really?  Do you need drivers to
know that the dependency is there?

Just add likns *before* even probing for drivers (yes, you can do that)
and the core will handle that for you.

> I guess I could amend portdrv to return -EPROBE_DEFER on Macs if
> no driver is bound to the NHI. Doesn't feel pretty to me though.
> 
> Ultimately this seems to be the same issue as with calling
> dev_pm_domain_set() for a bound device. Perhaps device_link_add()
> can likewise be allowed if a runtime PM ref is held for the devices
> and the call happens under lock_system_sleep()?

No, the whole synchronization scheme in the links code would have had to be
changed for that to really work.

And it really is about what is needed (at least in principle) to run your
device.  If you think you need device X with a driver to handle device Y
correctly, then either you need it all the time, from probe to remove, or
you just don't really need it at all.

Thanks,
Rafael


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Re: [PATCH v2 02/10] driver core: Functional dependencies tracking support

[Lukas Wunner]

On Thu, Jul 21, 2016 at 02:25:15AM +0200, Rafael J. Wysocki wrote:
> On Thursday, July 21, 2016 01:25:53 AM Lukas Wunner wrote:
> > On Thu, Jul 21, 2016 at 12:51:31AM +0200, Rafael J. Wysocki wrote:
> > > On Wednesday, July 20, 2016 05:23:40 PM Lukas Wunner wrote:
> > > > On Wed, Jul 20, 2016 at 02:52:42PM +0200, Rafael J. Wysocki wrote:
> > > > > On Wednesday, July 20, 2016 08:24:50 AM Lukas Wunner wrote:
> > > > > > On Wed, Jul 20, 2016 at 02:33:18AM +0200, Rafael J. Wysocki wrote:
> > > > > > > On Friday, June 17, 2016 04:07:38 PM Lukas Wunner wrote:
> > > > > > > > On Fri, Jun 17, 2016 at 02:54:56PM +0200, Rafael J. Wysocki wrote:
> > > > > > > > > On Fri, Jun 17, 2016 at 12:36 PM, Lukas Wunner <lukas@wunner.de> wrote:
> > > > > > > > > > On Fri, Jun 17, 2016 at 08:26:52AM +0200, Marek Szyprowski wrote:
> > > > > > > > > > > From: "Rafael J. Wysocki" <rafael.j.wysocki@intel.com>
> > > > > > > > > > We also have such a functional dependency for Thunderbolt on Macs:
> > > > > > > > > > On resume from system sleep, the PCIe hotplug ports may not resume
> > > > > > > > > > before the thunderbolt driver has reestablished the PCI tunnels.
> > > > > > > > > > Currently this is enforced by quirk_apple_wait_for_thunderbolt()
> > > > > > > > > > in drivers/pci/quirks.c. It would be good if we could represent
> > > > > > > > > > this dependency using something like Rafael's approach instead of
> > > > > > > > > > open coding it, however one detail in Rafael's patches is problematic:
> > > > > > > > > >
> > > > > > > > > > > New links are added by calling device_link_add() which may happen
> > > > > > > > > > > either before the consumer device is probed or when probing it, in
> > > > > > > > > > > which case the caller needs to ensure that the driver of the
> > > > > > > > > > > supplier device is present and functional and the DEVICE_LINK_PROBE_TIME
> > > > > > > > > > > flag should be passed to device_link_add() to reflect that.
> > > > > > > > > >
> > > > > > > > > > The thunderbolt driver cannot call device_link_add() before the
> > > > > > > > > > PCIe hotplug ports are bound to a driver unless we amend portdrv
> > > > > > > > > > to return -EPROBE_DEFER for Thunderbolt hotplug ports on Macs
> > > > > > > > > > if the thunderbolt driver isn't loaded.
> > > > > > > > > >
> > > > > > > > > > It would therefore be beneficial if device_link_add() can be
> > > > > > > > > > called even *after* the consumer is bound.
> > > > > > > > > 
> > > > > > > > > I don't quite follow.
> > > > > > > > > 
> > > > > > > > > Who's the provider and who's the consumer here?
> > > > > > > > 
> > > > > > > > thunderbolt.ko is the supplier.
> > > > > > > 
> > > > > > > But it binds to the children of the ports that are supposed to be its
> > > > > > > consumers?
> > > > > > > 
> > > > > > > Why is that even expected to work?
> > > > > > 
> > > > > > No, the consumers are aunts (or uncles) of the supplier, if you will. :-)
> > > > > > 
> > > > > > The consumers are the hotplug ports (named "Downstream Bridge 1 / 2" in
> > > > > > the drawing below). The supplier is the NHI:
> > > > > > 
> > > > > >       (Root Port) ---- Upstream Bridge --+-- Downstream Bridge 0 ---- NHI
> > > > > >                                          +-- Downstream Bridge 1 --
> > > > > >                                          +-- Downstream Bridge 2 --
> > > > > >                                          ...
> > > > > > 
> > > > > > We're calling pci_power_up() and pci_restore_state() from
> > > > > > pci_pm_resume_noirq(). And that will fail for devices below
> > > > > > the hotplug ports if the PCI tunnels haven't been re-established
> > > > > > yet by the NHI.
> > > > > 
> > > > > So the NHI is a PCIe device, right?
> > > > > 
> > > > > Does the Thunderbolt driver bind to that device?
> > > > 
> > > > The NHI is a PCI device but not a bridge. It has class 0x88000.
> > > > Yes, thunderbolt.ko binds to the NHI.
> > > > 
> > > > And portdrv binds to the upstream bridge and downstream bridges.
> > > > Those have class 0x60400.
> > > 
> > > OK, so why would there be a problem with creating links from the NHI
> > > (producer) to the ports (consumers) before binding portdrv to them?
> > 
> > Because the ordering in which drivers bind isn't guaranteed. At least
> > on my machine (Debian), portdrv always binds before thunderbolt.
> 
> But what drivers have to do with that really?  Do you need drivers to
> know that the dependency is there?
> 
> Just add likns *before* even probing for drivers (yes, you can do that)
> and the core will handle that for you.

Forgive me for being dense: How do you suggest to add links before
probing drivers? Only way I could think of is with a PCI quirk.

Which is what we're already doing right now (see drivers/pci/quirk.c:
quirk_apple_wait_for_thunderbolt()). And it ain't pretty.


> > I guess I could amend portdrv to return -EPROBE_DEFER on Macs if
> > no driver is bound to the NHI. Doesn't feel pretty to me though.
> > 
> > Ultimately this seems to be the same issue as with calling
> > dev_pm_domain_set() for a bound device. Perhaps device_link_add()
> > can likewise be allowed if a runtime PM ref is held for the devices
> > and the call happens under lock_system_sleep()?
> 
> No, the whole synchronization scheme in the links code would have had to be
> changed for that to really work.
> 
> And it really is about what is needed (at least in principle) to run your
> device.  If you think you need device X with a driver to handle device Y
> correctly, then either you need it all the time, from probe to remove, or
> you just don't really need it at all.

Real life isn't as simple as that.

In this case, we have consumers (hotplug ports) which are doing fine
if the driver for the supplier (NHI) is not loaded. But once it loads,
the links must be in place. Seems only logical to put the links in
place when they're needed, i.e. at load time of the supplier's driver.
Which the patch set doesn't allow right now.

Best regards,

Lukas

Re: [PATCH v2 02/10] driver core: Functional dependencies tracking support

[Rafael J. Wysocki]

On Monday, July 25, 2016 12:48:32 AM Lukas Wunner wrote:
> On Thu, Jul 21, 2016 at 02:25:15AM +0200, Rafael J. Wysocki wrote:
> > On Thursday, July 21, 2016 01:25:53 AM Lukas Wunner wrote:
> > > On Thu, Jul 21, 2016 at 12:51:31AM +0200, Rafael J. Wysocki wrote:
> > > > On Wednesday, July 20, 2016 05:23:40 PM Lukas Wunner wrote:
> > > > > On Wed, Jul 20, 2016 at 02:52:42PM +0200, Rafael J. Wysocki wrote:
> > > > > > On Wednesday, July 20, 2016 08:24:50 AM Lukas Wunner wrote:
> > > > > > > On Wed, Jul 20, 2016 at 02:33:18AM +0200, Rafael J. Wysocki wrote:
> > > > > > > > On Friday, June 17, 2016 04:07:38 PM Lukas Wunner wrote:
> > > > > > > > > On Fri, Jun 17, 2016 at 02:54:56PM +0200, Rafael J. Wysocki wrote:
> > > > > > > > > > On Fri, Jun 17, 2016 at 12:36 PM, Lukas Wunner <lukas@wunner.de> wrote:
> > > > > > > > > > > On Fri, Jun 17, 2016 at 08:26:52AM +0200, Marek Szyprowski wrote:
> > > > > > > > > > > > From: "Rafael J. Wysocki" <rafael.j.wysocki@intel.com>
> > > > > > > > > > > We also have such a functional dependency for Thunderbolt on Macs:
> > > > > > > > > > > On resume from system sleep, the PCIe hotplug ports may not resume
> > > > > > > > > > > before the thunderbolt driver has reestablished the PCI tunnels.
> > > > > > > > > > > Currently this is enforced by quirk_apple_wait_for_thunderbolt()
> > > > > > > > > > > in drivers/pci/quirks.c. It would be good if we could represent
> > > > > > > > > > > this dependency using something like Rafael's approach instead of
> > > > > > > > > > > open coding it, however one detail in Rafael's patches is problematic:
> > > > > > > > > > >
> > > > > > > > > > > > New links are added by calling device_link_add() which may happen
> > > > > > > > > > > > either before the consumer device is probed or when probing it, in
> > > > > > > > > > > > which case the caller needs to ensure that the driver of the
> > > > > > > > > > > > supplier device is present and functional and the DEVICE_LINK_PROBE_TIME
> > > > > > > > > > > > flag should be passed to device_link_add() to reflect that.
> > > > > > > > > > >
> > > > > > > > > > > The thunderbolt driver cannot call device_link_add() before the
> > > > > > > > > > > PCIe hotplug ports are bound to a driver unless we amend portdrv
> > > > > > > > > > > to return -EPROBE_DEFER for Thunderbolt hotplug ports on Macs
> > > > > > > > > > > if the thunderbolt driver isn't loaded.
> > > > > > > > > > >
> > > > > > > > > > > It would therefore be beneficial if device_link_add() can be
> > > > > > > > > > > called even *after* the consumer is bound.
> > > > > > > > > > 
> > > > > > > > > > I don't quite follow.
> > > > > > > > > > 
> > > > > > > > > > Who's the provider and who's the consumer here?
> > > > > > > > > 
> > > > > > > > > thunderbolt.ko is the supplier.
> > > > > > > > 
> > > > > > > > But it binds to the children of the ports that are supposed to be its
> > > > > > > > consumers?
> > > > > > > > 
> > > > > > > > Why is that even expected to work?
> > > > > > > 
> > > > > > > No, the consumers are aunts (or uncles) of the supplier, if you will. :-)
> > > > > > > 
> > > > > > > The consumers are the hotplug ports (named "Downstream Bridge 1 / 2" in
> > > > > > > the drawing below). The supplier is the NHI:
> > > > > > > 
> > > > > > >       (Root Port) ---- Upstream Bridge --+-- Downstream Bridge 0 ---- NHI
> > > > > > >                                          +-- Downstream Bridge 1 --
> > > > > > >                                          +-- Downstream Bridge 2 --
> > > > > > >                                          ...
> > > > > > > 
> > > > > > > We're calling pci_power_up() and pci_restore_state() from
> > > > > > > pci_pm_resume_noirq(). And that will fail for devices below
> > > > > > > the hotplug ports if the PCI tunnels haven't been re-established
> > > > > > > yet by the NHI.
> > > > > > 
> > > > > > So the NHI is a PCIe device, right?
> > > > > > 
> > > > > > Does the Thunderbolt driver bind to that device?
> > > > > 
> > > > > The NHI is a PCI device but not a bridge. It has class 0x88000.
> > > > > Yes, thunderbolt.ko binds to the NHI.
> > > > > 
> > > > > And portdrv binds to the upstream bridge and downstream bridges.
> > > > > Those have class 0x60400.
> > > > 
> > > > OK, so why would there be a problem with creating links from the NHI
> > > > (producer) to the ports (consumers) before binding portdrv to them?
> > > 
> > > Because the ordering in which drivers bind isn't guaranteed. At least
> > > on my machine (Debian), portdrv always binds before thunderbolt.
> > 
> > But what drivers have to do with that really?  Do you need drivers to
> > know that the dependency is there?
> > 
> > Just add likns *before* even probing for drivers (yes, you can do that)
> > and the core will handle that for you.
> 
> Forgive me for being dense: How do you suggest to add links before
> probing drivers? Only way I could think of is with a PCI quirk.
> 
> Which is what we're already doing right now (see drivers/pci/quirk.c:
> quirk_apple_wait_for_thunderbolt()). And it ain't pretty.

Well, maybe not, but doing it once during enumeration would be better than
on every resume.

Plus there is runtime PM to cover.

> > > I guess I could amend portdrv to return -EPROBE_DEFER on Macs if
> > > no driver is bound to the NHI. Doesn't feel pretty to me though.
> > > 
> > > Ultimately this seems to be the same issue as with calling
> > > dev_pm_domain_set() for a bound device. Perhaps device_link_add()
> > > can likewise be allowed if a runtime PM ref is held for the devices
> > > and the call happens under lock_system_sleep()?
> > 
> > No, the whole synchronization scheme in the links code would have had to be
> > changed for that to really work.
> > 
> > And it really is about what is needed (at least in principle) to run your
> > device.  If you think you need device X with a driver to handle device Y
> > correctly, then either you need it all the time, from probe to remove, or
> > you just don't really need it at all.
> 
> Real life isn't as simple as that.
> 
> In this case, we have consumers (hotplug ports) which are doing fine
> if the driver for the supplier (NHI) is not loaded. But once it loads,
> the links must be in place.

Hmm.

What if it is not loaded and the system suspends.  Will everything work
as expected after the subsequent resume?

Thanks,
Rafael

Re: [PATCH v2 02/10] driver core: Functional dependencies tracking support

[Lukas Wunner]

On Thu, Jul 28, 2016 at 02:30:31AM +0200, Rafael J. Wysocki wrote:
> On Monday, July 25, 2016 12:48:32 AM Lukas Wunner wrote:
> > On Thu, Jul 21, 2016 at 02:25:15AM +0200, Rafael J. Wysocki wrote:
> > > On Thursday, July 21, 2016 01:25:53 AM Lukas Wunner wrote:
> > > > I guess I could amend portdrv to return -EPROBE_DEFER on Macs if
> > > > no driver is bound to the NHI. Doesn't feel pretty to me though.
> > > > 
> > > > Ultimately this seems to be the same issue as with calling
> > > > dev_pm_domain_set() for a bound device. Perhaps device_link_add()
> > > > can likewise be allowed if a runtime PM ref is held for the devices
> > > > and the call happens under lock_system_sleep()?
> > > 
> > > No, the whole synchronization scheme in the links code would have had to be
> > > changed for that to really work.
> > > 
> > > And it really is about what is needed (at least in principle) to run your
> > > device.  If you think you need device X with a driver to handle device Y
> > > correctly, then either you need it all the time, from probe to remove, or
> > > you just don't really need it at all.
> > 
> > Real life isn't as simple as that.
> > 
> > In this case, we have consumers (hotplug ports) which are doing fine
> > if the driver for the supplier (NHI) is not loaded. But once it loads,
> > the links must be in place.
> 
> Hmm.
> 
> What if it is not loaded and the system suspends.  Will everything work
> as expected after the subsequent resume?

The short answer is yes.

Long answer:

With Thunderbolt, the switch fabric is told to set up PCI tunnels
through the NHI (Native Host Interface). Once set up, the tunnels
stay as they are and attached devices are reachable. However after
a power cycle of the controller (suspend/resume), the tunnels are
gone and need to be re-established.

On Macs, there are two software components communicating with the
NHI: The first one is an EFI driver which sets up tunnels to all
devices present on boot and lights up all attached DP-over-Thunderbolt
displays. Once ExitBootServices is called, the EFI driver is shut
down but the configured tunnels stay as they are. The kernel is thus
able to enumerate attached PCI devices.

The second component is the OS driver, thunderbolt.ko. It is needed
to set up tunnels to hot-plugged devices (i.e., not present at boot).
It is also needed to re-establish tunnels after suspend/resume.

The necessity of quirk_apple_wait_for_thunderbolt() arises because
we walk the entire PCI hierarchy during ->resume_noirq and call
pci_power_up() and pci_restore_state() for each device. Now remember,
the PCI tunnels are gone after a power cycle, so the attached devices
aren't reachable. Waking them and restoring their state will fail
unless the thunderbolt driver reconfigures the switch fabric first.

=> So if there are no devices attached and thunderbolt.ko isn't loaded,
   everything is fine. No device link needed.

=> If devices are attached and thunderbolt.ko is loaded, then the hotplug
   ports need to wait for re-establishment of the PCI tunnels.
   Device link is needed.

=> If devices were attached on boot and thunderbolt.ko isn't loaded, they
   will be unreachable after resume. Nothing we can do about that.
   No device link needed.

So this is a case of a "weak" device link, "weak" referring to the fact
that it's only needed if the supplier is bound.

All that said, I don't know if this case exists often enough that it's
worth making allowances for it in the driver core.

Sorry for the wall of text, just want to make sure we're on the same page
and all possible use cases of device links are discussed and considered.

Thanks,

Lukas

Re: [PATCH v2 02/10] driver core: Functional dependencies tracking support

[Rafael J. Wysocki]

On Thursday, July 28, 2016 05:28:31 PM Lukas Wunner wrote:
> On Thu, Jul 28, 2016 at 02:30:31AM +0200, Rafael J. Wysocki wrote:
> > On Monday, July 25, 2016 12:48:32 AM Lukas Wunner wrote:
> > > On Thu, Jul 21, 2016 at 02:25:15AM +0200, Rafael J. Wysocki wrote:
> > > > On Thursday, July 21, 2016 01:25:53 AM Lukas Wunner wrote:
> > > > > I guess I could amend portdrv to return -EPROBE_DEFER on Macs if
> > > > > no driver is bound to the NHI. Doesn't feel pretty to me though.
> > > > > 
> > > > > Ultimately this seems to be the same issue as with calling
> > > > > dev_pm_domain_set() for a bound device. Perhaps device_link_add()
> > > > > can likewise be allowed if a runtime PM ref is held for the devices
> > > > > and the call happens under lock_system_sleep()?
> > > > 
> > > > No, the whole synchronization scheme in the links code would have had to be
> > > > changed for that to really work.
> > > > 
> > > > And it really is about what is needed (at least in principle) to run your
> > > > device.  If you think you need device X with a driver to handle device Y
> > > > correctly, then either you need it all the time, from probe to remove, or
> > > > you just don't really need it at all.
> > > 
> > > Real life isn't as simple as that.
> > > 
> > > In this case, we have consumers (hotplug ports) which are doing fine
> > > if the driver for the supplier (NHI) is not loaded. But once it loads,
> > > the links must be in place.
> > 
> > Hmm.
> > 
> > What if it is not loaded and the system suspends.  Will everything work
> > as expected after the subsequent resume?
> 
> The short answer is yes.

OK

I think it's possible to add a link flag to address this case.

Namely, if that flag is passed to device_link_add(), the link will be
added in the DEVICE_LINK_ACTIVE state right away, but that will need to
be synchronized against all possible transitions of the consumer device
(at least).

It's better to do that in a separate patch for this reason IMO.

Thanks,
Rafael


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