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

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Thanks Andy for review. I have incorporated your comments and will be sending the patch soon.

On 5/11/24 11:12, Andy Shevchenko wrote:
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

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'

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.
I have incorporated this.

Signed-off-by: Krishna Kumar <krishnak@xxxxxxxxxxxxx>

+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()?
I have incorporated this.

+	/* 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);

+		/* 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;

Best Regards,


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