Re: [PATCH 2/2] arch/powerpc: hotplug driver bridge support

Andy Shevchenko
2024-05-11T05:42:57Z

Thu, May 09, 2024 at 05:35:54PM +0530, Krishna Kumar kirjoitti:
> There is an issue with the hotplug operation when it's done on the
> bridge/switch slot. The bridge-port and devices behind the bridge, which
> become offline by hot-unplug operation, don't get hot-plugged/enabled by
> doing hot-plug operation on that slot. Only the first port of the bridge
> gets enabled and the remaining port/devices remain unplugged. The hot
> plug/unplug operation is done by the hotplug driver
> (drivers/pci/hotplug/pnv_php.c).
>
> Root Cause Analysis: This behavior is due to missing code for the DPC
> switch/bridge. The existing driver depends on pci_hp_add_devices()
> function for device enablement. This function calls pci_scan_slot() on
> only one device-node/port of the bridge, not on all the siblings'
> device-node/port.
>
> The missing code needs to be added which will find all the sibling
> device-nodes/bridge-ports and will run explicit pci_scan_slot() on
> those. A new function has been added for this purpose which gets
> invoked from pci_hp_add_devices(). This new function
> pci_traverse_sibling_nodes_and_scan_slot() gets all the sibling
> bridge-ports by traversal and explicitly invokes pci_scan_slot on them.
>
>

One blank line is enough here.

> Signed-off-by: Krishna Kumar <krishnak@linux.ibm.com>

...

> +void *pci_traverse_sibling_nodes_and_scan_slot(struct device_node *start, struct pci_bus *bus)
> +{
> + struct device_node *dn;
> + struct device_node *parent;
> + int slotno;
> +
> + const __be32 *classp1;
> + u32 class1 = 0;

> + classp1 = of_get_property(start->child, "class-code", NULL);
> + if (classp1)
> + class1 = of_read_number(classp1, 1);

What's wrong with of_property_read_u32()?

> + /* Call of pci_scan_slot for non-bridge/EP case */
> + if (!((class1 >> 8) == PCI_CLASS_BRIDGE_PCI)) {
> + slotno = PCI_SLOT(PCI_DN(start->child)->devfn);
> + pci_scan_slot(bus, PCI_DEVFN(slotno, 0));
> + return NULL;
> + }
> +
> + /* Iterate all siblings */
> + parent = start;
> + for_each_child_of_node(parent, dn) {
> + const __be32 *classp;
> + u32 class = 0;
> +
> + classp = of_get_property(dn, "class-code", NULL);
> + if (classp)
> + class = of_read_number(classp, 1);

Ditto.

> + /* Call of pci_scan_slot on each sibling-nodes/bridge-ports */
> + if ((class >> 8) == PCI_CLASS_BRIDGE_PCI) {
> + slotno = PCI_SLOT(PCI_DN(dn)->devfn);
> + pci_scan_slot(bus, PCI_DEVFN(slotno, 0));
> + }
> + }
> +
> + return NULL;
> +}

--
With Best Regards,
Andy Shevchenko