From: Lukas Wunner <lukas@wunner.de>
To: "Rafael J. Wysocki" <rjw@rjwysocki.net>
Cc: Marek Szyprowski <m.szyprowski@samsung.com>,
"linux-pm@vger.kernel.org" <linux-pm@vger.kernel.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
"open list:AMD IOMMU (AMD-VI)" <iommu@lists.linux-foundation.org>,
linux-samsung-soc@vger.kernel.org,
"linux-arm-kernel@lists.infradead.org"
<linux-arm-kernel@lists.infradead.org>,
Joerg Roedel <joro@8bytes.org>, Inki Dae <inki.dae@samsung.com>,
Kukjin Kim <kgene@kernel.org>,
Krzysztof Kozlowski <k.kozlowski@samsung.com>,
Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>,
Ulf Hansson <ulf.hansson@linaro.org>,
Mark Brown <broonie@kernel.org>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
Andreas Noever <andreas.noever@gmail.com>,
linux-pci@vger.kernel.org
Subject: Re: [PATCH v2 02/10] driver core: Functional dependencies tracking support
Date: Wed, 20 Jul 2016 08:24:50 +0200 [thread overview]
Message-ID: <20160720062450.GA8066@wunner.de> (raw)
In-Reply-To: <1975118.iO8UCAENoH@vostro.rjw.lan>
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
next prev parent reply other threads:[~2016-07-20 6:25 UTC|newest]
Thread overview: 36+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-06-17 6:26 [PATCH v2 00/10] Exynos IOMMU: proper runtime PM support (use device dependencies) Marek Szyprowski
2016-06-17 6:26 ` [PATCH v2 01/10] driver core: Add a wrapper around __device_release_driver() Marek Szyprowski
2016-06-17 6:26 ` [PATCH v2 02/10] driver core: Functional dependencies tracking support Marek Szyprowski
2016-06-17 10:36 ` Lukas Wunner
2016-06-17 12:54 ` Rafael J. Wysocki
2016-06-17 14:07 ` Lukas Wunner
2016-07-20 0:33 ` Rafael J. Wysocki
2016-07-20 6:24 ` Lukas Wunner [this message]
2016-07-20 12:52 ` Rafael J. Wysocki
2016-07-20 15:23 ` Lukas Wunner
2016-07-20 22:51 ` Rafael J. Wysocki
2016-07-20 23:25 ` Lukas Wunner
2016-07-21 0:25 ` Rafael J. Wysocki
2016-07-24 22:48 ` Lukas Wunner
2016-07-28 0:30 ` Rafael J. Wysocki
2016-07-28 15:28 ` Lukas Wunner
2016-09-06 23:57 ` Rafael J. Wysocki
2016-06-17 6:26 ` [PATCH v2 03/10] PM core: Make async suspend/resume of devices use device links Marek Szyprowski
2016-06-17 6:26 ` [PATCH v2 04/10] PM core: Make runtime PM " Marek Szyprowski
2016-06-17 6:26 ` [PATCH v2 05/10] PM core: Optimize the use of device links for runtime PM Marek Szyprowski
2016-06-17 6:26 ` [PATCH v2 06/10] driver core: Avoid endless recursion if device has more than one link Marek Szyprowski
2016-09-06 23:09 ` Rafael J. Wysocki
2016-06-17 6:26 ` [PATCH v2 07/10] driver core: Add support for links to already probed drivers Marek Szyprowski
2016-09-06 23:13 ` Rafael J. Wysocki
2016-06-17 6:26 ` [PATCH v2 08/10] PM core: Fix restoring devices with links during system PM transition Marek Szyprowski
2016-09-06 23:24 ` Rafael J. Wysocki
2016-06-17 6:26 ` [PATCH v2 09/10] iommu/exynos: Remove excessive, useless debug Marek Szyprowski
2016-06-17 6:27 ` [PATCH v2 10/10] iommu/exynos: Add proper runtime pm support Marek Szyprowski
2016-07-14 15:41 ` [PATCH v2 00/10] Exynos IOMMU: proper runtime PM support (use device dependencies) Tobias Jakobi
2016-07-15 13:21 ` Tobias Jakobi
2016-07-18 10:32 ` Marek Szyprowski
2016-07-18 11:00 ` Tobias Jakobi
2016-07-18 13:50 ` Marek Szyprowski
2016-07-18 16:43 ` Tobias Jakobi
2016-07-19 6:26 ` Marek Szyprowski
2016-07-24 18:02 ` Tobias Jakobi
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