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



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