linux-kernel - Re: [PATCH v4 6/6] PCI: of: Create device-tree PCI host bridge node

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Message-ID: <20241204214852.GA3017210@bhelgaas>
Date: Wed, 4 Dec 2024 15:48:52 -0600
From: Bjorn Helgaas <helgaas@...nel.org>
To: Herve Codina <herve.codina@...tlin.com>
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	"Rafael J. Wysocki" <rafael@...nel.org>,
	Rob Herring <robh@...nel.org>,
	Saravana Kannan <saravanak@...gle.com>,
	Bjorn Helgaas <bhelgaas@...gle.com>, Lizhi Hou <lizhi.hou@....com>,
	linux-kernel@...r.kernel.org, devicetree@...r.kernel.org,
	linux-pci@...r.kernel.org,
	Allan Nielsen <allan.nielsen@...rochip.com>,
	Horatiu Vultur <horatiu.vultur@...rochip.com>,
	Steen Hegelund <steen.hegelund@...rochip.com>,
	Thomas Petazzoni <thomas.petazzoni@...tlin.com>
Subject: Re: [PATCH v4 6/6] PCI: of: Create device-tree PCI host bridge node

On Mon, Dec 02, 2024 at 02:15:18PM +0100, Herve Codina wrote:
> PCI devices device-tree nodes can be already created. This was
> introduced by commit 407d1a51921e ("PCI: Create device tree node for
> bridge").
> 
> In order to have device-tree nodes related to PCI devices attached on
> their PCI root bus (the PCI bus handled by the PCI host bridge), a PCI
> root bus device-tree node is needed. This root bus node will be used as
> the parent node of the first level devices scanned on the bus. On
> device-tree based systems, this PCI root bus device tree node is set to
> the node of the related PCI host bridge. The PCI host bridge node is
> available in the device-tree used to describe the hardware passed at
> boot.
> 
> On non device-tree based system (such as ACPI), a device-tree node for
> the PCI host bridge or for the root bus do not exist. Indeed, the PCI
> host bridge is not described in a device-tree used at boot simply
> because no device-tree are passed at boot.

s/do not exist/does not exist/

> +void of_pci_make_host_bridge_node(struct pci_host_bridge *bridge)
> +{
> +	struct device_node *np = NULL;
> +	struct of_changeset *cset;
> +	const char *name;
> +	int ret;
> +
> +	/*
> +	 * If there is already a device-tree node linked to the PCI bus handled
> +	 * by this bridge (i.e. the PCI root bus), nothing to do.
> +	 */
> +	if (pci_bus_to_OF_node(bridge->bus))
> +		return;
> +
> +	/* The root bus has no node. Check that the host bridge has no node too */
> +	if (bridge->dev.of_node) {
> +		pr_err("PCI host bridge of_node already set");

Can we use dev_err() here?

Bjorn