powerpc/pci: Remove OF node back pointer from pci_dn

The check_req() helper uses pci_get_pdn() to get an OF node pointer.
pci_get_pdn() returns a pci_dn pointer which either:
1) from the OF node returned by pci_device_to_OF_node();
2) from the parent child_list where entries don't have OF node pointers.
Since check_req() does not care about 2), it can call
pci_device_to_OF_node() directly, hence the change.

The find_pe_dn() helper uses embedded pci_dn to get an OF node which is
also stored in edev->pdev so let's take a shortcut and call
pci_device_to_OF_node() directly.

With these 2 changes, we can finally get rid of the OF node back pointer.
Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

arch/powerpc/include/asm/pci-bridge.h

@@ -195,7 +195,6 @@ struct pci_dn {
 	struct  pci_dn *parent;
 	struct  pci_controller *phb;	/* for pci devices */
 	struct	iommu_table_group *table_group;	/* for phb's or bridges */
-	struct	device_node *node;	/* back-pointer to the device_node */
 
 	int	pci_ext_config_space;	/* for pci devices */
 

arch/powerpc/kernel/pci_dn.c

@@ -293,7 +293,6 @@ struct pci_dn *pci_add_device_node_info(struct pci_controller *hose,
 	if (pdn == NULL)
 		return NULL;
 	dn->data = pdn;
-	pdn->node = dn;
 	pdn->phb = hose;
 #ifdef CONFIG_PPC_POWERNV
 	pdn->pe_number = IODA_INVALID_PE;

arch/powerpc/platforms/pseries/msi.c

@@ -132,15 +132,10 @@ static void rtas_teardown_msi_irqs(struct pci_dev *pdev)
 static int check_req(struct pci_dev *pdev, int nvec, char *prop_name)
 {
 	struct device_node *dn;
-	struct pci_dn *pdn;
 	const __be32 *p;
 	u32 req_msi;
 
-	pdn = pci_get_pdn(pdev);
-	if (!pdn)
-		return -ENODEV;
-
-	dn = pdn->node;
+	dn = pci_device_to_OF_node(pdev);
 
 	p = of_get_property(dn, prop_name, NULL);
 	if (!p) {
@@ -197,7 +192,6 @@ static struct device_node *find_pe_total_msi(struct pci_dev *dev, int *total)
 static struct device_node *find_pe_dn(struct pci_dev *dev, int *total)
 {
 	struct device_node *dn;
-	struct pci_dn *pdn;
 	struct eeh_dev *edev;
 
 	/* Found our PE and assume 8 at that point. */
@@ -210,8 +204,7 @@ static struct device_node *find_pe_dn(struct pci_dev *dev, int *total)
 	edev = pdn_to_eeh_dev(PCI_DN(dn));
 	if (edev->pe)
 		edev = list_first_entry(&edev->pe->edevs, struct eeh_dev, list);
-	pdn = eeh_dev_to_pdn(edev);
-	dn = pdn ? pdn->node : NULL;
+	dn = pci_device_to_OF_node(edev->pdev);
 	if (!dn)
 		return NULL;