diff --git a/sys/powerpc/powernv/opal.h b/sys/powerpc/powernv/opal.h
--- a/sys/powerpc/powernv/opal.h
+++ b/sys/powerpc/powernv/opal.h
@@ -56,6 +56,7 @@
 #define	OPAL_PCI_CONFIG_WRITE_HALF_WORD	17
 #define	OPAL_PCI_CONFIG_WRITE_WORD	18
 #define	OPAL_PCI_EEH_FREEZE_STATUS	23
+#define OPAL_CONSOLE_WRITE_BUFFER_SPACE 25
 #define	OPAL_PCI_EEH_FREEZE_CLEAR	26
 #define	OPAL_PCI_PHB_MMIO_ENABLE	27
 #define	OPAL_PCI_SET_PHB_MEM_WINDOW	28
diff --git a/sys/powerpc/powernv/opal_console.c b/sys/powerpc/powernv/opal_console.c
--- a/sys/powerpc/powernv/opal_console.c
+++ b/sys/powerpc/powernv/opal_console.c
@@ -171,6 +171,24 @@
 	mtx_unlock_spin(&opalcons_buffer.mtx);
 }
 
+static int64_t
+uart_opal_console_write_buffer_space(int vtermid)
+{
+	int64_t buffer_space_val = 0;
+	vm_paddr_t buffer_space_ptr;
+
+	if (pmap_bootstrapped)
+		buffer_space_ptr = vtophys(&buffer_space_val);
+	else
+		buffer_space_ptr = (vm_paddr_t)&buffer_space_val;
+
+	if (opal_call(OPAL_CONSOLE_WRITE_BUFFER_SPACE, vtermid,
+	    buffer_space_ptr) != OPAL_SUCCESS)
+		return (-1);
+
+	return (be64toh(buffer_space_val));
+}
+
 static int
 uart_opal_probe_node(struct uart_opal_softc *sc)
 {
@@ -420,12 +438,12 @@
 		len -= 4;
 	}
 
-#if 0
-	if (err != OPAL_SUCCESS)
-		len = 0;
-#endif
+	if (err == OPAL_SUCCESS)
+		return (len);
+	else if (err == OPAL_BUSY_EVENT)
+		return(0);
 
-	return (len);
+	return (-1);
 }
 
 static int
@@ -481,11 +499,28 @@
 	struct uart_opal_softc *sc;
 	char buffer[8];
 	int len;
+	int64_t buffer_space;
 
 	sc = tty_softc(tp);
 
-	while ((len = ttydisc_getc(tp, buffer, sizeof(buffer))) != 0)
-		uart_opal_put(sc, buffer, len);
+	while ((len = ttydisc_getc(tp, buffer, sizeof(buffer))) != 0) {
+		int bytes_written = 0;
+		while (bytes_written == 0) {
+			buffer_space = uart_opal_console_write_buffer_space(sc->vtermid);
+			if (buffer_space == -1)
+				/* OPAL failure or invalid terminal */
+				break;
+			else if (buffer_space >= len)
+				bytes_written = uart_opal_put(sc, buffer, len);
+
+			if (bytes_written == 0)
+				/* OPAL must be busy, poll and retry */
+				opal_call(OPAL_POLL_EVENTS, NULL);
+			else if (bytes_written == -1)
+				/* OPAL failure or invalid terminal */
+				break;
+		}
+	}
 }
 
 static void