linux-kernel - [PATCH] rpaphp: fix slot registration for multiple slots under a PHB

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Date:	Fri,  8 Jul 2016 18:19:47 -0500
From:	Tyrel Datwyler <tyreld@...ux.vnet.ibm.com>
To:	linux-pci@...r.kernel.org
Cc:	bhelgaas@...gle.com, mpe@...erman.id.au, benh@...nel.crashing.org,
	nfont@...ux.vnet.ibm.com, mdroth@...ux.vnet.ibm.com,
	linux-kernel@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org,
	Tyrel Datwyler <tyreld@...ux.vnet.ibm.com>
Subject: [PATCH] rpaphp: fix slot registration for multiple slots under a PHB

PowerVM seems to only ever provide a single hotplug slot per PHB.
The under lying slot hotplug registration code assumed multiple slots,
but the actual implementation is broken for multiple slots. This went
unnoticed for years due to the nature of PowerVM as mentioned
previously. Under qemu/kvm the hotplug slot model aligns more with
x86 where multiple slots are presented under a single PHB. As seen
in the following each additional slot after the first fails to
register due to each slot always being compared against the first
child node of the PHB in the device tree.

[    6.492291] rpaphp: RPA HOT Plug PCI Controller Driver version: 0.1
[    6.492569] rpaphp: Slot [Slot 0] registered
[    6.492577] rpaphp: pci_hp_register failed with error -16
[    6.493082] rpaphp: pci_hp_register failed with error -16
[    6.493138] rpaphp: pci_hp_register failed with error -16
[    6.493161] rpaphp: pci_hp_register failed with error -16

The registration logic is fixed so that each slot is compared
against the existing child devices of the PHB in the device tree to
determine present slots vs empty slots.

[   38.481750] rpaphp: RPA HOT Plug PCI Controller Driver version: 0.1
[   38.482004] rpaphp: Slot [C0] registered
[   38.482127] rpaphp: Slot [C1] registered
[   38.482241] rpaphp: Slot [C2] registered
[   38.482356] rpaphp: Slot [C3] registered
[   38.482495] rpaphp: Slot [C4] registered

Signed-off-by: Tyrel Datwyler <tyreld@...ux.vnet.ibm.com>
---
 drivers/pci/hotplug/rpaphp_slot.c | 17 ++++++++++++-----
 1 file changed, 12 insertions(+), 5 deletions(-)

diff --git a/drivers/pci/hotplug/rpaphp_slot.c b/drivers/pci/hotplug/rpaphp_slot.c
index 6937c72..c90fa8d 100644
--- a/drivers/pci/hotplug/rpaphp_slot.c
+++ b/drivers/pci/hotplug/rpaphp_slot.c
@@ -117,8 +117,10 @@ EXPORT_SYMBOL_GPL(rpaphp_deregister_slot);
 int rpaphp_register_slot(struct slot *slot)
 {
 	struct hotplug_slot *php_slot = slot->hotplug_slot;
+	struct device_node *child;
+	u32 my_index;
 	int retval;
-	int slotno;
+	int slotno = -1;
 
 	dbg("%s registering slot:path[%s] index[%x], name[%s] pdomain[%x] type[%d]\n",
 		__func__, slot->dn->full_name, slot->index, slot->name,
@@ -130,10 +132,15 @@ int rpaphp_register_slot(struct slot *slot)
 		return -EAGAIN;
 	}
 
-	if (slot->dn->child)
-		slotno = PCI_SLOT(PCI_DN(slot->dn->child)->devfn);
-	else
-		slotno = -1;
+	for_each_child_of_node(slot->dn, child) {
+		retval = of_property_read_u32(child, "my,ibm-drc-index", &my_index);
+		if (my_index == slot->index) {
+			slotno = PCI_SLOT(PCI_DN(child)->devfn);
+			of_node_put(child);
+			break;
+		}
+	}
+
 	retval = pci_hp_register(php_slot, slot->bus, slotno, slot->name);
 	if (retval) {
 		err("pci_hp_register failed with error %d\n", retval);
-- 
2.7.4