From: Herve Codina <herve.codina@bootlin.com>
To: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: "Rob Herring" <robh@kernel.org>,
"Rafael J. Wysocki" <rafael@kernel.org>,
"Bjorn Helgaas" <bhelgaas@google.com>,
"Lizhi Hou" <lizhi.hou@amd.com>, "Max Zhen" <max.zhen@amd.com>,
"Sonal Santan" <sonal.santan@amd.com>,
"Stefano Stabellini" <stefano.stabellini@xilinx.com>,
"Jonathan Cameron" <Jonathan.Cameron@huawei.com>,
"Krzysztof Wilczyński" <kwilczynski@kernel.org>,
linux-kernel@vger.kernel.org, linux-pci@vger.kernel.org,
"Allan Nielsen" <allan.nielsen@microchip.com>,
"Horatiu Vultur" <horatiu.vultur@microchip.com>,
"Steen Hegelund" <steen.hegelund@microchip.com>,
"Thomas Petazzoni" <thomas.petazzoni@bootlin.com>,
stable@vger.kernel.org
Subject: Re: [PATCH v3 2/2] PCI: of: Attach created of_node to existing device
Date: Fri, 12 Apr 2024 10:10:19 +0200 [thread overview]
Message-ID: <20240412101019.7ceee755@bootlin.com> (raw)
In-Reply-To: <2024041219-impure-upcountry-9e9d@gregkh>
Hi Greg, Rob,
On Fri, 12 Apr 2024 09:41:19 +0200
Greg Kroah-Hartman <gregkh@linuxfoundation.org> wrote:
> On Thu, Apr 11, 2024 at 03:34:49PM -0500, Rob Herring wrote:
> > On Thu, Apr 11, 2024 at 03:23:55PM +0200, Greg Kroah-Hartman wrote:
> > > On Mon, Mar 25, 2024 at 04:39:15PM +0100, Herve Codina wrote:
> > > > The commit 407d1a51921e ("PCI: Create device tree node for bridge")
> > > > creates of_node for PCI devices.
> > > >
> > > > During the insertion handling of these new DT nodes done by of_platform,
> > > > new devices (struct device) are created. For each PCI devices a struct
> > > > device is already present (created and handled by the PCI core).
> > > > Having a second struct device to represent the exact same PCI device is
> > > > not correct.
> > > >
> > > > On the of_node creation:
> > > > - tell the of_platform that there is no need to create a device for this
> > > > node (OF_POPULATED flag),
> > > > - link this newly created of_node to the already present device,
> > > > - tell fwnode that the device attached to this of_node is ready using
> > > > fwnode_dev_initialized().
> > > >
> > > > With this fix, the of_node are available in the sysfs device tree:
> > > > /sys/devices/platform/soc/d0070000.pcie/
> > > > + of_node -> .../devicetree/base/soc/pcie@d0070000
> > > > + pci0000:00
> > > > + 0000:00:00.0
> > > > + of_node -> .../devicetree/base/soc/pcie@d0070000/pci@0,0
> > > > + 0000:01:00.0
> > > > + of_node -> .../devicetree/base/soc/pcie@d0070000/pci@0,0/dev@0,0
> > > >
> > > > On the of_node removal, revert the operations.
> > > >
> > > > Fixes: 407d1a51921e ("PCI: Create device tree node for bridge")
> > > > Cc: stable@vger.kernel.org
> > > > Signed-off-by: Herve Codina <herve.codina@bootlin.com>
> > >
> > > I need an ack from the maintainer here before I can take this.
> >
> > Correct me if I'm wrong, but having the of_node sysfs link populated or
> > changed after device_add is a race we lost. Userspace is notified about
> > the new device and then some time later the symlink shows up.
>
> Ah, yes, I missed that, good catch, this will not work.
>
> > However, it so far is not appearing that there's an easy way to
> > reshuffle order of things to fix this.
> >
> > Maybe the short term (and stable) answer just don't create any of_node
> > symlinks on these dynamically created nodes.
>
> That would work, but does userspace really need to know this
> information?
>
I don't think that the user space really need this information.
I agree, it should work.
Let me rework my series in that sense and perform some tests before
sending a new iteration removing the of_node sysfs link creation.
Best regards,
Hervé
next prev parent reply other threads:[~2024-04-12 8:10 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-03-25 15:39 [PATCH v3 0/2] Attach DT nodes to existing PCI devices Herve Codina
2024-03-25 15:39 ` [PATCH v3 1/2] driver core: Introduce device_{add,remove}_of_node() Herve Codina
2024-03-25 15:39 ` [PATCH v3 2/2] PCI: of: Attach created of_node to existing device Herve Codina
2024-04-11 13:23 ` Greg Kroah-Hartman
2024-04-11 20:34 ` Rob Herring
2024-04-12 7:41 ` Greg Kroah-Hartman
2024-04-12 8:10 ` Herve Codina [this message]
2024-04-08 12:43 ` [PATCH v3 0/2] Attach DT nodes to existing PCI devices Herve Codina
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