linux-kernel - Re: [PATCH v4] PCI/PM: Prevent runtime suspend before devices are fully initialized

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Message-ID: <20260114164538.GA816227@bhelgaas>
Date: Wed, 14 Jan 2026 10:45:38 -0600
From: Bjorn Helgaas <helgaas@...nel.org>
To: Marek Szyprowski <m.szyprowski@...sung.com>
Cc: Brian Norris <briannorris@...omium.org>,
	Bjorn Helgaas <bhelgaas@...gle.com>, Lukas Wunner <lukas@...ner.de>,
	linux-kernel@...r.kernel.org, linux-pci@...r.kernel.org,
	linux-pm@...r.kernel.org, "Rafael J . Wysocki" <rafael@...nel.org>,
	Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>
Subject: Re: [PATCH v4] PCI/PM: Prevent runtime suspend before devices are
 fully initialized

On Wed, Jan 14, 2026 at 10:46:41AM +0100, Marek Szyprowski wrote:
> On 06.01.2026 23:27, Bjorn Helgaas wrote:
> > On Thu, Oct 23, 2025 at 02:09:01PM -0700, Brian Norris wrote:
> >> Today, it's possible for a PCI device to be created and
> >> runtime-suspended before it is fully initialized. When that happens, the
> >> device will remain in D0, but the suspend process may save an
> >> intermediate version of that device's state -- for example, without
> >> appropriate BAR configuration. When the device later resumes, we'll
> >> restore invalid PCI state and the device may not function.
> ...

> >      Link: https://patch.msgid.link/20251023140901.v4.1.I60a53c170a8596661883bd2b4ef475155c7aa72b@changeid
> 
> This patch landed recently in linux-next as commit c796513dc54e 
> ("PCI/PM: Prevent runtime suspend until devices are fully initialized"). 
> In my tests I found that it sometimes causes the "pci 0000:01:00.0: 
> runtime PM trying to activate child device 0000:01:00.0 but parent 
> (0000:00:00.0) is not active" warning on Qualcomm Robotics RB5 board 
> (arch/arm64/boot/dts/qcom/qrb5165-rb5.dts). This in turn causes a 
> lockdep warning about console lock, but this is just a consequence of 
> the runtime pm warning. Reverting $subject patch on top of current 
> linux-next hides this warning.

I moved this patch from pci/pm to pci/pend to remove it from
linux-next while we figure this out.  Thanks for the report and
debugging!

Bjorn