ntb: ntb_test: ensure the link is up before trying to configure the mws

After the link tests, there is a race on one side of the test for
the link coming up. It's possible, in some cases, for the test script
to write to the 'peer_trans' files before the link has come up.

To fix this, we simply use the link event file to ensure both sides
see the link as up before continuning.

Signed-off-by: Logan Gunthorpe <logang@deltatee.com>
Acked-by: Allen Hubbe <Allen.Hubbe@dell.com>
Signed-off-by: Jon Mason <jdmason@kudzu.us>
Fixes: a9c59ef77458 ("ntb_test: Add a selftest script for the NTB subsystem")

tools/testing/selftests/ntb/ntb_test.sh

@@ -333,6 +333,10 @@ function ntb_tool_tests()
 	link_test $LOCAL_TOOL $REMOTE_TOOL
 	link_test $REMOTE_TOOL $LOCAL_TOOL
 
+	#Ensure the link is up on both sides before continuing
+	write_file Y $LOCAL_TOOL/link_event
+	write_file Y $REMOTE_TOOL/link_event
+
 	for PEER_TRANS in $(ls $LOCAL_TOOL/peer_trans*); do
 		PT=$(basename $PEER_TRANS)
 		write_file $MW_SIZE $LOCAL_TOOL/$PT