powerpc/eeh: Don't unfreeze PHB PE after reset

On PowerNV platform, the PE is kept in frozen state until the PE
reset is completed to avoid recursive EEH error caused by MMIO
access during the period of EEH reset. The PE's frozen state is
cleared after BARs of PCI device included in the PE are restored
and enabled. However, we needn't clear the frozen state for PHB PE
explicitly at this point as there is no real PE for PHB PE. As the
PHB PE is always binding with PE#0, we actually clear PE#0, which
is wrong. It doesn't incur any problem though.

This checks if the PE is PHB PE and doesn't clear the frozen state
if it is.

Signed-off-by: Gavin Shan <gwshan@linux.vnet.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

arch/powerpc/kernel/eeh_driver.c

@@ -587,10 +587,16 @@ static int eeh_reset_device(struct eeh_pe *pe, struct pci_bus *bus)
 	eeh_ops->configure_bridge(pe);
 	eeh_pe_restore_bars(pe);
 
-	/* Clear frozen state */
-	rc = eeh_clear_pe_frozen_state(pe, false);
-	if (rc)
-		return rc;
+	/*
+	 * If it's PHB PE, the frozen state on all available PEs should have
+	 * been cleared by the PHB reset. Otherwise, we unfreeze the PE and its
+	 * child PEs because they might be in frozen state.
+	 */
+	if (!(pe->type & EEH_PE_PHB)) {
+		rc = eeh_clear_pe_frozen_state(pe, false);
+		if (rc)
+			return rc;
+	}
 
 	/* Give the system 5 seconds to finish running the user-space
 	 * hotplug shutdown scripts, e.g. ifdown for ethernet.  Yes,