rapidio: add device access check into the enumeration

Add explicit device access check before performing device enumeration.
This gives a chance to clear possible link error conditions by issuing
safe maintenance read request(s).

Signed-off-by: Alexandre Bounine <alexandre.bounine@idt.com>
Cc: Thomas Moll <thomas.moll@sysgo.com>
Cc: Matt Porter <mporter@kernel.crashing.org>
Cc: Li Yang <leoli@freescale.com>
Cc: Kumar Gala <galak@kernel.crashing.org>
Cc: Micha Nelissen <micha@neli.hopto.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

drivers/rapidio/rio-scan.c

@@ -762,6 +762,12 @@ static int __devinit rio_enum_peer(struct rio_net *net, struct rio_mport *port,
 	u16 destid;
 	int tmp;
 
+	if (rio_mport_chk_dev_access(port,
+			RIO_ANY_DESTID(port->sys_size), hopcount)) {
+		pr_debug("RIO: device access check failed\n");
+		return -1;
+	}
+
 	if (rio_get_host_deviceid_lock(port, hopcount) == port->host_deviceid) {
 		pr_debug("RIO: PE already discovered by this host\n");
 		/*

drivers/rapidio/rio.c

@@ -546,7 +546,7 @@ err_out:
  * @destid: Device destination ID in network
  * @hopcount: Number of hops into the network
  */
-static int
+int
 rio_mport_chk_dev_access(struct rio_mport *mport, u16 destid, u8 hopcount)
 {
 	int i = 0;

drivers/rapidio/rio.h

@@ -24,6 +24,8 @@ extern u32 rio_mport_get_physefb(struct rio_mport *port, int local,
 				 u16 destid, u8 hopcount);
 extern u32 rio_mport_get_efb(struct rio_mport *port, int local, u16 destid,
 			     u8 hopcount, u32 from);
+extern int rio_mport_chk_dev_access(struct rio_mport *mport, u16 destid,
+				    u8 hopcount);
 extern int rio_create_sysfs_dev_files(struct rio_dev *rdev);
 extern int rio_enum_mport(struct rio_mport *mport);
 extern int rio_disc_mport(struct rio_mport *mport);