On Wed, Nov 16, 2022 at 8:09 PM Liu Peibao <liupeibao@xxxxxxxxxxx> wrote:
>
> Add a mechanism to disable on chip PCI devices by DT. Typically, when there
> are pins shareable between the platform device and the on chip PCI device,
> if the PCI device is not preferred, add `status = "disabled"` property to
> this PCI device DT node.
>
> For example, on LS2K1000, GMAC1 (on chip PCI device) and GPIO (platform
> device, not PCI device) 14 share the same pin. If GMAC1 is not preferred,
> add `status = "disabled"` property in GMAC1 DT node.
>
> Signed-off-by: Liu Peibao <liupeibao@xxxxxxxxxxx>
> ---
> V5 -> V6: 1. rewrite the commit log to make things clear.
> 2. replace "unavailable" as "disabled" in patch subject.
> V4 -> V5: clear the issue we are facing in commit log.
> 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
This should not be controller specific as a disabled node should be
honored on any platform. It also makes assumptions about how the PCI
scanning code works that PCI_VENDOR_ID read failing is enough to stop
scanning. Can you please test this patch I just sent[1].
Rob
[1] https://lore.kernel.org/all/20230210164351.2687475-1-robh@xxxxxxxxxx/
