2 files changed, 10 insertions, 1 deletions

diff --git a/share/man/man4/ciss.4 b/share/man/man4/ciss.4
index a896e4e61575..74e54e7b692d 100644
--- a/share/man/man4/ciss.4
+++ b/share/man/man4/ciss.4
@@ -84,6 +84,12 @@ drives) are only exposed as
 devices.
 Hot-insertion and removal of devices is supported but a bus
 rescan might be necessary.
+.Pp
+The problem which adapter freezes with the message
+.Dq ADAPTER HEARTBEAT FAILED
+might be solved by updating the firmware and/or setting the
+.Va hw.ciss.nop_message_heartbeat
+tunable to non-zero at boot time.
 .Sh HARDWARE
 Controllers supported by the
 .Nm
diff --git a/sys/dev/ciss/ciss.c b/sys/dev/ciss/ciss.c
index 9c9214955a6e..c71d0d9b5600 100644
--- a/sys/dev/ciss/ciss.c
+++ b/sys/dev/ciss/ciss.c
@@ -247,6 +247,9 @@ static struct cdevsw ciss_cdevsw = {
 static unsigned int ciss_expose_hidden_physical = 0;
 TUNABLE_INT("hw.ciss.expose_hidden_physical", &ciss_expose_hidden_physical);
 
+static unsigned int ciss_nop_message_heartbeat = 0;
+TUNABLE_INT("hw.ciss.nop_message_heartbeat", &ciss_nop_message_heartbeat);
+
 /************************************************************************
  * CISS adapters amazingly don't have a defined programming interface
  * value.  (One could say some very despairing things about PCI and
@@ -3099,7 +3102,7 @@ ciss_periodic(void *arg)
     /*
      * Send the NOP message and wait for a response.
      */
-    if ((error = ciss_get_request(sc, &cr)) == 0) {
+    if (ciss_nop_message_heartbeat != 0 && (error = ciss_get_request(sc, &cr)) == 0) {
 	cc = CISS_FIND_COMMAND(cr);
 	cr->cr_complete = ciss_nop_complete;
 	cc->cdb.cdb_length = 1;