powerpc/pseries/eeh: Fix crash when error happens during device probe

EEH may happen during a PCI driver probe. If the driver is trying to
access some register in a loop, the EEH code will try to print the
driver name. But the driver pointer in struct pci_dev is not set until
probe returns successfully.

Use a function to test if the device and the driver pointer is NULL
before accessing the driver's name.
Signed-off-by: NThadeu Lima de Souza Cascardo <cascardo@linux.vnet.ibm.com>
Signed-off-by: NBenjamin Herrenschmidt <benh@kernel.crashing.org>

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

@@ -142,6 +142,11 @@ static inline const char *eeh_pci_name(struct pci_dev *pdev)
 	return pdev ? pci_name(pdev) : "<null>";
 } 
 
+static inline const char *eeh_driver_name(struct pci_dev *pdev)
+{
+	return (pdev && pdev->driver) ? pdev->driver->name : "<null>";
+}
+
 #endif /* CONFIG_EEH */
 
 #else /* CONFIG_PCI */

arch/powerpc/platforms/pseries/eeh.c

@@ -551,9 +551,9 @@ int eeh_dn_check_failure(struct device_node *dn, struct pci_dev *dev)
 			printk (KERN_ERR "EEH: %d reads ignored for recovering device at "
 				"location=%s driver=%s pci addr=%s\n",
 				pdn->eeh_check_count, location,
-				dev->driver->name, eeh_pci_name(dev));
+				eeh_driver_name(dev), eeh_pci_name(dev));
 			printk (KERN_ERR "EEH: Might be infinite loop in %s driver\n",
-				dev->driver->name);
+				eeh_driver_name(dev));
 			dump_stack();
 		}
 		goto dn_unlock;