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

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Date:   Wed, 10 Nov 2021 11:59:29 -0600
From:   Bjorn Helgaas <helgaas@...nel.org>
To:     "Rafael J. Wysocki" <rafael@...nel.org>
Cc:     Robert Święcki <robert@...ecki.net>,
        Uwe Kleine-König 
        <u.kleine-koenig@...gutronix.de>,
        linux-i2c <linux-i2c@...r.kernel.org>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        Linux PCI <linux-pci@...r.kernel.org>,
        Linux PM <linux-pm@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Subject: Re: [PATCH] pci: Don't call resume callback for nearly bound devices

On Wed, Nov 10, 2021 at 05:48:52PM +0100, Rafael J. Wysocki wrote:
> On Wed, Nov 10, 2021 at 5:33 PM Robert Święcki <robert@...ecki.net> wrote:
> > śr., 10 lis 2021 o 15:14 Bjorn Helgaas <helgaas@...nel.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@...nel.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.
> 
> So I honestly think that commit 2a4d9408c9e8 needs to be reverted,
> because it clearly does more than it is supposed to and we need to go
> back to the drawing board and do this again, but correctly.

Yep, I agree, I'll work on that today.

Bjorn