linux-kernel - Re: [PATCH] PCI/pwrctrl: Only destroy alongside host bridge

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Message-ID: <aHbGax-7CiRmnKs7@google.com>
Date: Tue, 15 Jul 2025 14:21:47 -0700
From: Brian Norris <briannorris@...omium.org>
To: Manivannan Sadhasivam <mani@...nel.org>
Cc: Bartosz Golaszewski <brgl@...ev.pl>,
	Bjorn Helgaas <bhelgaas@...gle.com>, linux-pci@...r.kernel.org,
	Rob Herring <robh@...nel.org>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] PCI/pwrctrl: Only destroy alongside host bridge

Hi Manivannan,

Thanks for reviewing.

On Sat, Jul 12, 2025 at 10:56:38PM +0530, Manivannan Sadhasivam wrote:
> If you take a look at commit f1536585588b ("PCI: Don't rely on
> of_platform_depopulate() for reused OF-nodes"), you can realize that the PCI
> core clears OF_POPULATED flag while removing the PCI device. So
> of_platform_device_destroy() will do nothing.

I've looked through that commit several times, and while I think I
understand its claim, I really haven't been able to validate it. I've
inspected the code for anything like of_node_clear_flag(nc,
OF_POPULATED), and the closest I see for any PCI-relevant code is in
drivers/of/platform.c -- mostly in error paths (undoing device creation)
or of_platform_device_destroy() or of_platform_depopulate().

I've also tried quite a bit of tracing / printk'ing, and I can't find
the OF_POPULATED getting cleared either.

Is there any chance there's a mistake in the claims in commit
f1536585588b? e.g., maybe Bartosz was looking at OF_POPULATED_BUS (which
is different, but also relevant to his change)? Or am I missing
something obvious in here?

OTOH, I also see that part of my change is not really doing quite what I
thought it was -- so far, I think there may be some kind of resource
leak (kobj ref), since I'm not seeing pci_release_host_bridge_dev()
called when I think it should be. If I perform cleanup in
pci_free_host_bridge() instead, then I do indeed see
of_platform_device_destroy() tear things down the way I expect.

Brian