Improve the NT partition state transition ops

When one host and its peer are trying to do NT partition state
transitions for some NT partition setup operations on a single
partition, they may conflict with each other and step onto each other's
toes. These NT partition setup operations include requester ID setup
and memory windows setup.

We introduced some checks to ensure that we only do the NT partition
state transitions when the peer is not doing. When seeing a conflict we
will retry after a short delay.

Author: kelvin-cao

ntb_hw_switchtec.c

@@ -134,9 +134,9 @@ static struct switchtec_ntb *ntb_sndev(struct ntb_dev *ntb)
 	return container_of(ntb, struct switchtec_ntb, ntb);
 }
 
-static int switchtec_ntb_part_op(struct switchtec_ntb *sndev,
-				 struct ntb_ctrl_regs __iomem *ctl,
-				 u32 op, int wait_status)
+static int switchtec_ntb_part_op_no_retry(struct switchtec_ntb *sndev,
+					  struct ntb_ctrl_regs __iomem *ctl,
+					  u32 op, int wait_status)
 {
 	static const char * const op_text[] = {
 		[NTB_CTRL_PART_OP_LOCK] = "lock",
@@ -147,6 +147,24 @@ static int switchtec_ntb_part_op(struct switchtec_ntb *sndev,
 	int i;
 	u32 ps;
 	int status;
+	int part_id, locked_part_id;
+	int xlink_peer = ctl == sndev->mmio_xlink_peer_ctrl ? 1 : 0;
+
+	ps = ioread32(&ctl->partition_status);
+
+	locked_part_id = (ps & 0xFF0000) >> 16;
+	part_id = (ps & 0xFF000000) >> 24;
+
+	ps &= 0xFFFF;
+
+	if (ps != NTB_CTRL_PART_STATUS_NORMAL &&
+	    ps != NTB_CTRL_PART_STATUS_LOCKED)
+		return -EAGAIN;
+
+	if (ps == NTB_CTRL_PART_STATUS_LOCKED)
+		if ((xlink_peer && (locked_part_id != part_id)) ||
+		    (!xlink_peer && (locked_part_id != sndev->self_partition)))
+			return -EAGAIN;
 
 	switch (op) {
 	case NTB_CTRL_PART_OP_LOCK:
@@ -170,12 +188,24 @@ static int switchtec_ntb_part_op(struct switchtec_ntb *sndev,
 			return -EINTR;
 		}
 
-		ps = ioread32(&ctl->partition_status) & 0xFFFF;
+		ps = ioread32(&ctl->partition_status);
+
+		locked_part_id = (ps & 0xFF0000) >> 16;
+		part_id = (ps & 0xFF000000) >> 24;
+
+		ps &= 0xFFFF;
 
 		if (ps != status)
 			break;
 	}
 
+	if (ps == NTB_CTRL_PART_STATUS_LOCKED) {
+		if ((xlink_peer && (locked_part_id != part_id)) ||
+		    (!xlink_peer &&
+		     (locked_part_id != sndev->self_partition)))
+			return -EAGAIN;
+	}
+
 	if (ps == wait_status)
 		return 0;
 
@@ -191,6 +221,28 @@ static int switchtec_ntb_part_op(struct switchtec_ntb *sndev,
 	return -EIO;
 }
 
+static int switchtec_ntb_part_op(struct switchtec_ntb *sndev,
+				 struct ntb_ctrl_regs __iomem *ctl,
+				 u32 op, int wait_status)
+{
+	int rc;
+	int i = 0;
+
+	while (i++ < 10) {
+		rc = switchtec_ntb_part_op_no_retry(sndev, ctl, op,
+						    wait_status);
+		if (rc == -EAGAIN) {
+			if (msleep_interruptible(30) != 0)
+				return -EINTR;
+			continue;
+		}
+
+		break;
+	}
+
+	return rc;
+}
+
 static int switchtec_ntb_send_msg(struct switchtec_ntb *sndev, int idx,
 				  u32 val)
 {