Re: [PATCH V4] PCI: loongson: Skip scanning unavailable child devices

[Bjorn Helgaas <helgaas@kernel.org>]

On Tue, Nov 08, 2022 at 02:42:40PM +0800, Liu Peibao wrote:
> The PCI Controller of 2k1000 could not mask devices by setting vender ID or
> device ID in configuration space header as invalid values. When there are
> pins shareable between the platform device and PCI device, if the platform
> device is preferred, we should not scan this PCI device. In the above
> scene, add `status = "disabled"` property in DT node of this PCI device.
> 
> Signed-off-by: Liu Peibao <liupeibao@loongson.cn>
> ---
> V3 -> V4: 1. get rid of the masklist and search the status property
> 	  directly.
>           2. check the status property only when accessing the vendor ID.
> V2 -> V3: 1. use list_for_each_entry() for more clearly.
>           2. fix wrong use of sizeof().
> V1 -> V2: use existing property "status" instead of adding new property.
> 
>  drivers/pci/controller/pci-loongson.c | 11 +++++++++++
>  1 file changed, 11 insertions(+)
> 
> diff --git a/drivers/pci/controller/pci-loongson.c b/drivers/pci/controller/pci-loongson.c
> index 05c50408f13b..efca0b3b5a29 100644
> --- a/drivers/pci/controller/pci-loongson.c
> +++ b/drivers/pci/controller/pci-loongson.c
> @@ -194,6 +194,17 @@ static void __iomem *pci_loongson_map_bus(struct pci_bus *bus,
>  			return NULL;
>  	}
>  
> +#ifdef CONFIG_OF
> +	/* Don't access disabled devices. */
> +	if (pci_is_root_bus(bus) && where == PCI_VENDOR_ID) {
> +		struct device_node *dn;
> +
> +		dn = of_pci_find_child_device(bus->dev.of_node, devfn);
> +		if (dn && !of_device_is_available(dn))
> +			return NULL;
> +	}
> +#endif

Looks nice and simple, thanks for trying this out.

>  	/* CFG0 can only access standard space */
>  	if (where < PCI_CFG_SPACE_SIZE && priv->cfg0_base)
>  		return cfg0_map(priv, bus, devfn, where);
> -- 
> 2.20.1
>