powerpc/eeh: Fix crash when adding a device in a slot with DDW

The DDW code uses a eeh_dev struct from the pci_dev. However, this is
not set until eeh_add_device_late is called.

Since pci_bus_add_devices is called before eeh_add_device_late, the PCI
devices are added to the bus, making drivers' probe hooks to be called.
These will call set_dma_mask, which will call the DDW code, which will
require the eeh_dev struct from pci_dev. This would result in a crash,
due to a NULL dereference.

Calling eeh_add_device_late after pci_bus_add_devices would make the
system BUG, because device files shouldn't be added to devices there
were not added to the system. So, a new function is needed to add such
files only after pci_bus_add_devices have been called.

Cc: stable@vger.kernel.org
Signed-off-by: Thadeu Lima de Souza Cascardo <cascardo@linux.vnet.ibm.com>
Acked-by: Gavin Shan <shangw@linux.vnet.ibm.com>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

arch/powerpc/kernel/of_platform.c

@@ -91,6 +91,9 @@ static int of_pci_phb_probe(struct platform_device *dev)
 	/* Add probed PCI devices to the device model */
 	pci_bus_add_devices(phb->bus);
 
+	/* sysfs files should only be added after devices are added */
+	eeh_add_sysfs_files(phb->bus);
+
 	return 0;
 }