IB/qib: Allow PSM to select from multiple port assignment algorithms

We used to allow only full specification, or using all contexts within
an HCA before moving to the next HCA.  We now allow an additional
method -- round-robining through HCAs -- and make that the default.

Signed-off-by: Dave Olson <dave.olson@qlogic.com>
Signed-off-by: Roland Dreier <rolandd@cisco.com>

2 files changed, 118 insertions, 101 deletions

diff --git a/drivers/infiniband/hw/qib/qib_common.h b/drivers/infiniband/hw/qib/qib_common.h
index b3955ed8f79..145da404088 100644
--- a/drivers/infiniband/hw/qib/qib_common.h
+++ b/drivers/infiniband/hw/qib/qib_common.h
@@ -279,7 +279,7 @@ struct qib_base_info {
  * may not be implemented; the user code must deal with this if it
  * cares, or it must abort after initialization reports the difference.
  */
-#define QIB_USER_SWMINOR 10
+#define QIB_USER_SWMINOR 11
 
 #define QIB_USER_SWVERSION ((QIB_USER_SWMAJOR << 16) | QIB_USER_SWMINOR)
 
@@ -302,6 +302,18 @@ struct qib_base_info {
 #define QIB_KERN_SWVERSION ((QIB_KERN_TYPE << 31) | QIB_USER_SWVERSION)
 
 /*
+ * If the unit is specified via open, HCA choice is fixed.  If port is
+ * specified, it's also fixed.  Otherwise we try to spread contexts
+ * across ports and HCAs, using different algorithims.  WITHIN is
+ * the old default, prior to this mechanism.
+ */
+#define QIB_PORT_ALG_ACROSS 0 /* round robin contexts across HCAs, then
+			       * ports; this is the default */
+#define QIB_PORT_ALG_WITHIN 1 /* use all contexts on an HCA (round robin
+			       * active ports within), then next HCA */
+#define QIB_PORT_ALG_COUNT 2 /* number of algorithm choices */
+
+/*
  * This structure is passed to qib_userinit() to tell the driver where
  * user code buffers are, sizes, etc.   The offsets and sizes of the
  * fields must remain unchanged, for binary compatibility.  It can
@@ -319,7 +331,7 @@ struct qib_user_info {
 	/* size of struct base_info to write to */
 	__u32 spu_base_info_size;
 
-	__u32 _spu_unused3;
+	__u32 spu_port_alg; /* which QIB_PORT_ALG_*; unused user minor < 11 */
 
 	/*
 	 * If two or more processes wish to share a context, each process
diff --git a/drivers/infiniband/hw/qib/qib_file_ops.c b/drivers/infiniband/hw/qib/qib_file_ops.c
index a142a9eb522..6b11645edf3 100644
--- a/drivers/infiniband/hw/qib/qib_file_ops.c
+++ b/drivers/infiniband/hw/qib/qib_file_ops.c
@@ -1294,128 +1294,130 @@ bail:
 	return ret;
 }
 
-static inline int usable(struct qib_pportdata *ppd, int active_only)
+static inline int usable(struct qib_pportdata *ppd)
 {
 	struct qib_devdata *dd = ppd->dd;
-	u32 linkok = active_only ? QIBL_LINKACTIVE :
-		 (QIBL_LINKINIT | QIBL_LINKARMED | QIBL_LINKACTIVE);
 
 	return dd && (dd->flags & QIB_PRESENT) && dd->kregbase && ppd->lid &&
-		(ppd->lflags & linkok);
+		(ppd->lflags & QIBL_LINKACTIVE);
 }
 
-static int find_free_ctxt(int unit, struct file *fp,
-			  const struct qib_user_info *uinfo)
+/*
+ * Select a context on the given device, either using a requested port
+ * or the port based on the context number.
+ */
+static int choose_port_ctxt(struct file *fp, struct qib_devdata *dd, u32 port,
+			    const struct qib_user_info *uinfo)
 {
-	struct qib_devdata *dd = qib_lookup(unit);
 	struct qib_pportdata *ppd = NULL;
-	int ret;
-	u32 ctxt;
+	int ret, ctxt;
 
-	if (!dd || (uinfo->spu_port && uinfo->spu_port > dd->num_pports)) {
-		ret = -ENODEV;
-		goto bail;
-	}
-
-	/*
-	 * If users requests specific port, only try that one port, else
-	 * select "best" port below, based on context.
-	 */
-	if (uinfo->spu_port) {
-		ppd = dd->pport + uinfo->spu_port - 1;
-		if (!usable(ppd, 0)) {
+	if (port) {
+		if (!usable(dd->pport + port - 1)) {
 			ret = -ENETDOWN;
-			goto bail;
-		}
+			goto done;
+		} else
+			ppd = dd->pport + port - 1;
 	}
-
-	for (ctxt = dd->first_user_ctxt; ctxt < dd->cfgctxts; ctxt++) {
-		if (dd->rcd[ctxt])
-			continue;
-		/*
-		 * The setting and clearing of user context rcd[x] protected
-		 * by the qib_mutex
-		 */
-		if (!ppd) {
-			/* choose port based on ctxt, if up, else 1st up */
-			ppd = dd->pport + (ctxt % dd->num_pports);
-			if (!usable(ppd, 0)) {
-				int i;
-				for (i = 0; i < dd->num_pports; i++) {
-					ppd = dd->pport + i;
-					if (usable(ppd, 0))
-						break;
-				}
-				if (i == dd->num_pports) {
-					ret = -ENETDOWN;
-					goto bail;
-				}
-			}
+	for (ctxt = dd->first_user_ctxt; ctxt < dd->cfgctxts && dd->rcd[ctxt];
+	     ctxt++)
+		;
+	if (ctxt == dd->cfgctxts) {
+		ret = -EBUSY;
+		goto done;
+	}
+	if (!ppd) {
+		u32 pidx = ctxt % dd->num_pports;
+		if (usable(dd->pport + pidx))
+			ppd = dd->pport + pidx;
+		else {
+			for (pidx = 0; pidx < dd->num_pports && !ppd;
+			     pidx++)
+				if (usable(dd->pport + pidx))
+					ppd = dd->pport + pidx;
 		}
-		ret = setup_ctxt(ppd, ctxt, fp, uinfo);
-		goto bail;
 	}
-	ret = -EBUSY;
+	ret = ppd ? setup_ctxt(ppd, ctxt, fp, uinfo) : -ENETDOWN;
+done:
+	return ret;
+}
+
+static int find_free_ctxt(int unit, struct file *fp,
+			  const struct qib_user_info *uinfo)
+{
+	struct qib_devdata *dd = qib_lookup(unit);
+	int ret;
+
+	if (!dd || (uinfo->spu_port && uinfo->spu_port > dd->num_pports))
+		ret = -ENODEV;
+	else
+		ret = choose_port_ctxt(fp, dd, uinfo->spu_port, uinfo);
 
-bail:
 	return ret;
 }
 
-static int get_a_ctxt(struct file *fp, const struct qib_user_info *uinfo)
+static int get_a_ctxt(struct file *fp, const struct qib_user_info *uinfo,
+		      unsigned alg)
 {
-	struct qib_pportdata *ppd;
-	int ret = 0, devmax;
-	int npresent, nup;
-	int ndev;
+	struct qib_devdata *udd = NULL;
+	int ret = 0, devmax, npresent, nup, ndev, dusable = 0, i;
 	u32 port = uinfo->spu_port, ctxt;
 
 	devmax = qib_count_units(&npresent, &nup);
+	if (!npresent) {
+		ret = -ENXIO;
+		goto done;
+	}
+	if (nup == 0) {
+		ret = -ENETDOWN;
+		goto done;
+	}
 
-	for (ndev = 0; ndev < devmax; ndev++) {
-		struct qib_devdata *dd = qib_lookup(ndev);
-
-		/* device portion of usable() */
-		if (!(dd && (dd->flags & QIB_PRESENT) && dd->kregbase))
-			continue;
-		for (ctxt = dd->first_user_ctxt; ctxt < dd->cfgctxts; ctxt++) {
-			if (dd->rcd[ctxt])
+	if (alg == QIB_PORT_ALG_ACROSS) {
+		unsigned inuse = ~0U;
+		/* find device (with ACTIVE ports) with fewest ctxts in use */
+		for (ndev = 0; ndev < devmax; ndev++) {
+			struct qib_devdata *dd = qib_lookup(ndev);
+			unsigned cused = 0, cfree = 0;
+			if (!dd)
 				continue;
-			if (port) {
-				if (port > dd->num_pports)
-					continue;
-				ppd = dd->pport + port - 1;
-				if (!usable(ppd, 0))
-					continue;
-			} else {
-				/*
-				 * choose port based on ctxt, if up, else
-				 * first port that's up for multi-port HCA
-				 */
-				ppd = dd->pport + (ctxt % dd->num_pports);
-				if (!usable(ppd, 0)) {
-					int j;
-
-					ppd = NULL;
-					for (j = 0; j < dd->num_pports &&
-						!ppd; j++)
-						if (usable(dd->pport + j, 0))
-							ppd = dd->pport + j;
-					if (!ppd)
-						continue; /* to next unit */
-				}
+			if (port && port <= dd->num_pports &&
+			    usable(dd->pport + port - 1))
+				dusable = 1;
+			else
+				for (i = 0; i < dd->num_pports; i++)
+					if (usable(dd->pport + i))
+						dusable++;
+			if (!dusable)
+				continue;
+			for (ctxt = dd->first_user_ctxt; ctxt < dd->cfgctxts;
+			     ctxt++)
+				if (dd->rcd[ctxt])
+					cused++;
+				else
+					cfree++;
+			if (cfree && cused < inuse) {
+				udd = dd;
+				inuse = cused;
 			}
-			ret = setup_ctxt(ppd, ctxt, fp, uinfo);
+		}
+		if (udd) {
+			ret = choose_port_ctxt(fp, udd, port, uinfo);
 			goto done;
 		}
+	} else {
+		for (ndev = 0; ndev < devmax; ndev++) {
+			struct qib_devdata *dd = qib_lookup(ndev);
+			if (dd) {
+				ret = choose_port_ctxt(fp, dd, port, uinfo);
+				if (!ret)
+					goto done;
+				if (ret == -EBUSY)
+					dusable++;
+			}
+		}
 	}
-
-	if (npresent) {
-		if (nup == 0)
-			ret = -ENETDOWN;
-		else
-			ret = -EBUSY;
-	} else
-		ret = -ENXIO;
+	ret = dusable ? -EBUSY : -ENETDOWN;
 
 done:
 	return ret;
@@ -1481,7 +1483,7 @@ static int qib_assign_ctxt(struct file *fp, const struct qib_user_info *uinfo)
 {
 	int ret;
 	int i_minor;
-	unsigned swmajor, swminor;
+	unsigned swmajor, swminor, alg = QIB_PORT_ALG_ACROSS;
 
 	/* Check to be sure we haven't already initialized this file */
 	if (ctxt_fp(fp)) {
@@ -1498,6 +1500,9 @@ static int qib_assign_ctxt(struct file *fp, const struct qib_user_info *uinfo)
 
 	swminor = uinfo->spu_userversion & 0xffff;
 
+	if (swminor >= 11 && uinfo->spu_port_alg < QIB_PORT_ALG_COUNT)
+		alg = uinfo->spu_port_alg;
+
 	mutex_lock(&qib_mutex);
 
 	if (qib_compatible_subctxts(swmajor, swminor) &&
@@ -1514,7 +1519,7 @@ static int qib_assign_ctxt(struct file *fp, const struct qib_user_info *uinfo)
 	if (i_minor)
 		ret = find_free_ctxt(i_minor - 1, fp, uinfo);
 	else
-		ret = get_a_ctxt(fp, uinfo);
+		ret = get_a_ctxt(fp, uinfo, alg);
 
 done_chk_sdma:
 	if (!ret) {
@@ -1862,7 +1867,7 @@ static int disarm_req_delay(struct qib_ctxtdata *rcd)
 {
 	int ret = 0;
 
-	if (!usable(rcd->ppd, 1)) {
+	if (!usable(rcd->ppd)) {
 		int i;
 		/*
 		 * if link is down, or otherwise not usable, delay
@@ -1881,7 +1886,7 @@ static int disarm_req_delay(struct qib_ctxtdata *rcd)
 				set_bit(_QIB_EVENT_DISARM_BUFS_BIT,
 					&rcd->user_event_mask[i]);
 		}
-		for (i = 0; !usable(rcd->ppd, 1) && i < 300; i++)
+		for (i = 0; !usable(rcd->ppd) && i < 300; i++)
 			msleep(100);
 		ret = -ENETDOWN;
 	}