Re: [PATCH] pci: controller: mobiveil: Hold reference returned by of_parse_phandle()

[Bjorn Helgaas <helgaas@kernel.org>]

On Mon, Jul 04, 2022 at 02:26:08PM +0800, Liang He wrote:
> In ls_g4_pcie_probe(), we should hold the reference returned by
> of_parse_phandle() and use it to call of_node_put() for refcount
> balance.
> 
> Fixes: d29ad70a813b ("PCI: mobiveil: Add PCIe Gen4 RC driver for Layerscape SoCs")
> Co-authored-by: Miaoqian Lin <linmq006@gmail.com>
> Signed-off-by: Liang He <windhl@126.com>
> ---
>  drivers/pci/controller/mobiveil/pcie-layerscape-gen4.c | 6 ++++--
>  1 file changed, 4 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/pci/controller/mobiveil/pcie-layerscape-gen4.c b/drivers/pci/controller/mobiveil/pcie-layerscape-gen4.c
> index d7b7350f02dd..075aa487f92e 100644
> --- a/drivers/pci/controller/mobiveil/pcie-layerscape-gen4.c
> +++ b/drivers/pci/controller/mobiveil/pcie-layerscape-gen4.c
> @@ -204,13 +204,15 @@ static int __init ls_g4_pcie_probe(struct platform_device *pdev)
>  	struct pci_host_bridge *bridge;
>  	struct mobiveil_pcie *mv_pci;
>  	struct ls_g4_pcie *pcie;
> -	struct device_node *np = dev->of_node;
> +	struct device_node *np = dev->of_node, *parse_np;
>  	int ret;
>  
> -	if (!of_parse_phandle(np, "msi-parent", 0)) {
> +	parse_np = of_parse_phandle(np, "msi-parent", 0);

I don't understand what's going on here.  Where is "msi-parent"
actually used?  If we just need to know whether "msi-parent" exists,
can we use of_property_read_bool() instead?  Or can we call
of_parse_phandle() closer to where it is used?  

> +	if (!parse_np) {
>  		dev_err(dev, "Failed to find msi-parent\n");
>  		return -EINVAL;
>  	}
> +	of_node_put(parse_np);
>  
>  	bridge = devm_pci_alloc_host_bridge(dev, sizeof(*pcie));
>  	if (!bridge)
> -- 
> 2.25.1
>