powerpc/kernel: Change retrieval of pci_dn

For a PCI device it's pci_dn can be retrieved from
pdev->dev.archdata.firmware_data, PCI_DN(devnode), or parent's list.
Thus, we should just use the existing function pci_get_pdn_by_devfn
to get the pci_dn.

Signed-off-by: Bryant G. Ly <bryantly@linux.vnet.ibm.com>
Reviewed-by: Sam Bobroff <sam.bobroff@au1.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

arch/powerpc/kernel/rtas_pci.c

@@ -91,26 +91,14 @@ static int rtas_pci_read_config(struct pci_bus *bus,
 				unsigned int devfn,
 				int where, int size, u32 *val)
 {
-	struct device_node *busdn, *dn;
 	struct pci_dn *pdn;
-	bool found = false;
 	int ret;
 
-	/* Search only direct children of the bus */
 	*val = 0xFFFFFFFF;
-	busdn = pci_bus_to_OF_node(bus);
-	for (dn = busdn->child; dn; dn = dn->sibling) {
-		pdn = PCI_DN(dn);
-		if (pdn && pdn->devfn == devfn
-		    && of_device_is_available(dn)) {
-			found = true;
-			break;
-		}
-	}
 
-	if (!found)
+	pdn = pci_get_pdn_by_devfn(bus, devfn);
-		return PCIBIOS_DEVICE_NOT_FOUND;
 
+	/* Validity of pdn is checked in here */
 	ret = rtas_read_config(pdn, where, size, val);
 	if (*val == EEH_IO_ERROR_VALUE(size) &&
 	    eeh_dev_check_failure(pdn_to_eeh_dev(pdn)))
@@ -153,24 +141,11 @@ static int rtas_pci_write_config(struct pci_bus *bus,
 				 unsigned int devfn,
 				 int where, int size, u32 val)
 {
-	struct device_node *busdn, *dn;
 	struct pci_dn *pdn;
-	bool found = false;
 
-	/* Search only direct children of the bus */
+	pdn = pci_get_pdn_by_devfn(bus, devfn);
-	busdn = pci_bus_to_OF_node(bus);
-	for (dn = busdn->child; dn; dn = dn->sibling) {
-		pdn = PCI_DN(dn);
-		if (pdn && pdn->devfn == devfn
-		    && of_device_is_available(dn)) {
-			found = true;
-			break;
-		}
-	}
-
-	if (!found)
-		return PCIBIOS_DEVICE_NOT_FOUND;
 
+	/* Validity of pdn is checked in here. */
 	return rtas_write_config(pdn, where, size, val);
 }