powerpc/powernv: Drop config requests in EEH accessors

It's bad idea to access the PCI config registers of the adapters,
which is experiencing reset. It leads to recursive EEH error without
exception. The patch drops PCI config requests in EEH accessors if
the PE has been marked to accept PCI config requests, for example
during PE reseet time.
Signed-off-by: Gavin Shan <gwshan@linux.vnet.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

arch/powerpc/platforms/powernv/eeh-powernv.c

@@ -383,6 +383,39 @@ static int powernv_eeh_err_inject(struct eeh_pe *pe, int type, int func,
 	return ret;
 }
 
+static inline bool powernv_eeh_cfg_blocked(struct device_node *dn)
+{
+	struct eeh_dev *edev = of_node_to_eeh_dev(dn);
+
+	if (!edev || !edev->pe)
+		return false;
+
+	if (edev->pe->state & EEH_PE_CFG_BLOCKED)
+		return true;
+
+	return false;
+}
+
+static int powernv_eeh_read_config(struct device_node *dn,
+				   int where, int size, u32 *val)
+{
+	if (powernv_eeh_cfg_blocked(dn)) {
+		*val = 0xFFFFFFFF;
+		return PCIBIOS_SET_FAILED;
+	}
+
+	return pnv_pci_cfg_read(dn, where, size, val);
+}
+
+static int powernv_eeh_write_config(struct device_node *dn,
+				    int where, int size, u32 val)
+{
+	if (powernv_eeh_cfg_blocked(dn))
+		return PCIBIOS_SET_FAILED;
+
+	return pnv_pci_cfg_write(dn, where, size, val);
+}
+
 /**
  * powernv_eeh_next_error - Retrieve next EEH error to handle
  * @pe: Affected PE
@@ -440,8 +473,8 @@ static struct eeh_ops powernv_eeh_ops = {
 	.get_log                = powernv_eeh_get_log,
 	.configure_bridge       = powernv_eeh_configure_bridge,
 	.err_inject		= powernv_eeh_err_inject,
-	.read_config            = pnv_pci_cfg_read,
-	.write_config           = pnv_pci_cfg_write,
+	.read_config            = powernv_eeh_read_config,
+	.write_config           = powernv_eeh_write_config,
 	.next_error		= powernv_eeh_next_error,
 	.restore_config		= powernv_eeh_restore_config
 };