Re: [PATCH] pci: Don't call resume callback for nearly bound devices

From: Bjorn Helgaas <helgaas@kernel.org>
To: "Robert Święcki" <robert@swiecki.net>
Cc: "Uwe Kleine-König" <u.kleine-koenig@pengutronix.de>,
	linux-i2c <linux-i2c@vger.kernel.org>,
	"Bjorn Helgaas" <bhelgaas@google.com>,
	"Linux PCI" <linux-pci@vger.kernel.org>,
	"Linux PM" <linux-pm@vger.kernel.org>,
	"Linux Kernel Mailing List" <linux-kernel@vger.kernel.org>,
	"Greg Kroah-Hartman" <gregkh@linuxfoundation.org>,
	"Rafael J. Wysocki" <rafael@kernel.org>
Subject: Re: [PATCH] pci: Don't call resume callback for nearly bound devices
Date: Thu, 11 Nov 2021 11:01:27 -0600	[thread overview]
Message-ID: <20211111170127.GA1336355@bhelgaas> (raw)
In-Reply-To: <20211110211905.GA1261732@bhelgaas>

On Wed, Nov 10, 2021 at 03:19:05PM -0600, Bjorn Helgaas wrote:
> On Wed, Nov 10, 2021 at 05:33:11PM +0100, Robert Święcki wrote:
> > śr., 10 lis 2021 o 15:14 Bjorn Helgaas <helgaas@kernel.org> napisał(a):
> > > On Tue, Nov 09, 2021 at 02:05:18PM -0600, Bjorn Helgaas wrote:
> > > > On Tue, Nov 09, 2021 at 07:58:47PM +0100, Rafael J. Wysocki wrote:
> > > > > On Tue, Nov 9, 2021 at 7:52 PM Rafael J. Wysocki <rafael@kernel.org> wrote:
> > > > > > ...
> > >
> > > > > > So instead, we can drop the pm_runtime_get_sync() and
> > > > > > pm_runtime_put_sync() from local_pci_probe() and pci_device_remove(),
> > > > > > respectively, and add pm_runtine_get_noresume() to pci_pm_init(),
> > > > > > which will prevent PM-runtime from touching the device until it has a
> > > > > > driver that supports PM-runtime.
> > > > > >
> > > > > > We'll lose the theoretical ability to put unbound devices into D3 this
> > > > > > way, but we learned some time ago that this isn't safe in all cases
> > > > > > anyway.
> > > > >
> > > > > IOW, something like this (untested and most likely white-space-damaged).
> > > >
> > > > Thanks!  I applied this manually to for-linus in hopes of making the
> > > > the next linux-next build.
> > > >
> > > > Please send any testing reports and corrections to the patch and
> > > > commit log!
> > >
> > > Robert, I hate to ask even more of you, but if you have a chance, it
> > > would be very helpful if you could test the patch below.  I'm pretty
> > > sure it should fix the problem you saw, and I hope to ask Linus to
> > > merge it today.
> > 
> > I think the most recent patch creates some timeouts and other problems
> > in pci-related code? Things I haven't seen before. But, granted, my
> > kernel testing approach is not with focus on details, so maybe I did
> > sth wrong.
> 
> Thank you very much for testing this.  The patch changed the way we
> use runtime PM, and the dmesg snippets below look like they could be
> related to runtime PM issues.
> 
> I think the conclusion is that we need to revert these commits:
> 
>   b5f9c644eb1b ("PCI: Remove struct pci_dev->driver")
>   2a4d9408c9e8 ("PCI: Use to_pci_driver() instead of pci_dev->driver")
> 
> from Linus' tree.  I queued up those reverts on
> https://git.kernel.org/pub/scm/linux/kernel/git/helgaas/pci.git/log/?h=for-linus

These reverts appeared in the Nov 11 linux-next tree.  Any chance you
could verify that they solve the i2c_dw_pci_resume() issue?  If it's
easier, you can apply them from:
https://git.kernel.org/pub/scm/linux/kernel/git/helgaas/pci.git/log/?h=for-linus
instead.

Bjorn