Fix a couple of mps problems.

When the driver is completely saturated with commands (1024 in the
case of the SAS2008 in my test system), I/O stops.  If we tell CAM
that we have one less command slot than we have actually allocated,
everything works fine.  We also need a few extra command slots to
allow for aborts and other task management commands to be sent down.

This needs more investigation to determine the root cause, but for
now this fixes things in my testing.

mps.c:		Change a printf() to mps_printf().

mps_sas.c:	Subtract 5 command slots when we tell CAM how many
		commands we can handle.

		Add some commented-out logic to print the contents
		the CDBs for timed-out commands.  This can help
		in debugging devices that are timing out.  This
		will be uncommented once I bring some CAM changes in.

Reported by:	Andrew Boyer <aboyer at averesystems dot com>

2 files changed, 39 insertions, 4 deletions

diff --git a/sys/dev/mps/mps.c b/sys/dev/mps/mps.c
index d0129e9..d57c7df 100644
--- a/sys/dev/mps/mps.c
+++ b/sys/dev/mps/mps.c
@@ -1416,7 +1416,7 @@ mps_data_cb(void *arg, bus_dma_segment_t *segs, int nsegs, int error)
 			chain = mps_alloc_chain(sc);
 			if (chain == NULL) {
 				/* Resource shortage, roll back! */
-				printf("out of chain frames\n");
+				mps_printf(sc, "out of chain frames\n");
 				return;
 			}
 
diff --git a/sys/dev/mps/mps_sas.c b/sys/dev/mps/mps_sas.c
index 5d29c9d..f13d304 100644
--- a/sys/dev/mps/mps_sas.c
+++ b/sys/dev/mps/mps_sas.c
@@ -596,6 +596,7 @@ mps_attach_sas(struct mps_softc *sc)
 {
 	struct mpssas_softc *sassc;
 	int error = 0;
+	int num_sim_reqs;
 
 	mps_dprint(sc, MPS_TRACE, "%s\n", __func__);
 
@@ -605,15 +606,30 @@ mps_attach_sas(struct mps_softc *sc)
 	sc->sassc = sassc;
 	sassc->sc = sc;
 
-	if ((sassc->devq = cam_simq_alloc(sc->num_reqs)) == NULL) {
+	/*
+	 * Tell CAM that we can handle 5 fewer requests than we have
+	 * allocated.  If we allow the full number of requests, all I/O
+	 * will halt when we run out of resources.  Things work fine with
+	 * just 1 less request slot given to CAM than we have allocated.
+	 * We also need a couple of extra commands so that we can send down
+	 * abort, reset, etc. requests when commands time out.  Otherwise
+	 * we could wind up in a situation with sc->num_reqs requests down
+	 * on the card and no way to send an abort.
+	 *
+	 * XXX KDM need to figure out why I/O locks up if all commands are
+	 * used.
+	 */
+	num_sim_reqs = sc->num_reqs - 5;
+
+	if ((sassc->devq = cam_simq_alloc(num_sim_reqs)) == NULL) {
 		mps_dprint(sc, MPS_FAULT, "Cannot allocate SIMQ\n");
 		error = ENOMEM;
 		goto out;
 	}
 
 	sassc->sim = cam_sim_alloc(mpssas_action, mpssas_poll, "mps", sassc,
-	    device_get_unit(sc->mps_dev), &sc->mps_mtx, sc->num_reqs, sc->num_reqs,
-	    sassc->devq);
+	    device_get_unit(sc->mps_dev), &sc->mps_mtx, num_sim_reqs,
+	    num_sim_reqs, sassc->devq);
 	if (sassc->sim == NULL) {
 		mps_dprint(sc, MPS_FAULT, "Cannot allocate SIM\n");
 		error = EINVAL;
@@ -930,6 +946,9 @@ mpssas_scsiio_timeout(void *data)
 	struct mps_softc *sc;
 	struct mps_command *cm;
 	struct mpssas_target *targ;
+#if 0
+	char cdb_str[(SCSI_MAX_CDBLEN * 3) + 1];
+#endif
 
 	cm = (struct mps_command *)data;
 	sc = cm->cm_sc;
@@ -954,6 +973,22 @@ mpssas_scsiio_timeout(void *data)
 
 	xpt_print(ccb->ccb_h.path, "SCSI command timeout on device handle "
 		  "0x%04x SMID %d\n", targ->handle, cm->cm_desc.Default.SMID);
+	/*
+	 * XXX KDM this is useful for debugging purposes, but the existing
+	 * scsi_op_desc() implementation can't handle a NULL value for
+	 * inq_data.  So this will remain commented out until I bring in
+	 * those changes as well.
+	 */
+#if 0
+	xpt_print(ccb->ccb_h.path, "Timed out command: %s. CDB %s\n",
+		  scsi_op_desc((ccb->ccb_h.flags & CAM_CDB_POINTER) ?
+		  		ccb->csio.cdb_io.cdb_ptr[0] :
+				ccb->csio.cdb_io.cdb_bytes[0], NULL),
+		  scsi_cdb_string((ccb->ccb_h.flags & CAM_CDB_POINTER) ?
+				   ccb->csio.cdb_io.cdb_ptr :
+				   ccb->csio.cdb_io.cdb_bytes, cdb_str,
+		  		   sizeof(cdb_str)));
+#endif
 
 	/* Inform CAM about the timeout and that recovery is starting. */
 #if 0