[PATCH v2 3/9] ppc/pnv: use dev->parent_bus->parent to get the PHB

[Daniel Henrique Barboza <danielhb413@gmail.com>]

It is not advisable to execute an object_dynamic_cast() to poke into
bus->qbus.parent and follow it up with a C cast into the PnvPHB type we
think we got.

A better way is to access the PnvPHB object via a QOM macro accessing
the existing parent links of the DeviceState. For a given
pnv-phb3/4-root-port 'dev', dev->parent_bus will give us the PHB bus,
and dev->parent_bus->parent is the PHB. Use the adequate QOM macro to
assert the type, and keep the NULL check in case we didn't get the
object we were expecting.

Signed-off-by: Daniel Henrique Barboza <danielhb413@gmail.com>
---
 hw/pci-host/pnv_phb3.c | 10 +++++++---
 hw/pci-host/pnv_phb4.c | 10 +++++++---
 2 files changed, 14 insertions(+), 6 deletions(-)

diff --git a/hw/pci-host/pnv_phb3.c b/hw/pci-host/pnv_phb3.c
index 4ba660f8b9..5e7f827415 100644
--- a/hw/pci-host/pnv_phb3.c
+++ b/hw/pci-host/pnv_phb3.c
@@ -1139,12 +1139,16 @@ static void pnv_phb3_root_port_realize(DeviceState *dev, Error **errp)
 {
     PCIERootPortClass *rpc = PCIE_ROOT_PORT_GET_CLASS(dev);
     PCIDevice *pci = PCI_DEVICE(dev);
-    PCIBus *bus = pci_get_bus(pci);
     PnvPHB3 *phb = NULL;
     Error *local_err = NULL;
 
-    phb = (PnvPHB3 *) object_dynamic_cast(OBJECT(bus->qbus.parent),
-                                          TYPE_PNV_PHB3);
+    /*
+     * dev->parent_bus gives access to the pnv-phb-root bus.
+     * The PnvPHB3 is the owner (parent) of the bus.
+     */
+    if (dev->parent_bus) {
+        phb = PNV_PHB3(dev->parent_bus->parent);
+    }
 
     if (!phb) {
         error_setg(errp,
diff --git a/hw/pci-host/pnv_phb4.c b/hw/pci-host/pnv_phb4.c
index ffd9d8a947..a0ee52e820 100644
--- a/hw/pci-host/pnv_phb4.c
+++ b/hw/pci-host/pnv_phb4.c
@@ -1782,12 +1782,16 @@ static void pnv_phb4_root_port_realize(DeviceState *dev, Error **errp)
 {
     PCIERootPortClass *rpc = PCIE_ROOT_PORT_GET_CLASS(dev);
     PCIDevice *pci = PCI_DEVICE(dev);
-    PCIBus *bus = pci_get_bus(pci);
     PnvPHB4 *phb = NULL;
     Error *local_err = NULL;
 
-    phb = (PnvPHB4 *) object_dynamic_cast(OBJECT(bus->qbus.parent),
-                                          TYPE_PNV_PHB4);
+    /*
+     * dev->parent_bus gives access to the pnv-phb-root bus.
+     * The PnvPHB4 is the owner (parent) of the bus.
+     */
+    if (dev->parent_bus) {
+        phb = PNV_PHB4(dev->parent_bus->parent);
+    }
 
     if (!phb) {
         error_setg(errp, "%s must be connected to pnv-phb4 buses", dev->id);
-- 
2.36.1