2 files changed, 25 insertions, 1 deletions
diff --git a/drivers/tty/hvc/hvc_dcc.c b/drivers/tty/hvc/hvc_dcc.c
index 44fbeba..3502a7b 100644
--- a/drivers/tty/hvc/hvc_dcc.c
+++ b/drivers/tty/hvc/hvc_dcc.c
@@ -86,6 +86,21 @@ static int hvc_dcc_get_chars(uint32_t vt, char *buf, int count)
 	return i;
 }
 
+static bool hvc_dcc_check(void)
+{
+	unsigned long time = jiffies + (HZ / 10);
+
+	/* Write a test character to check if it is handled */
+	__dcc_putchar('\n');
+
+	while (time_is_after_jiffies(time)) {
+		if (!(__dcc_getstatus() & DCC_STATUS_TX))
+			return true;
+	}
+
+	return false;
+}
+
 static const struct hv_ops hvc_dcc_get_put_ops = {
 	.get_chars = hvc_dcc_get_chars,
 	.put_chars = hvc_dcc_put_chars,
@@ -93,6 +108,9 @@ static const struct hv_ops hvc_dcc_get_put_ops = {
 
 static int __init hvc_dcc_console_init(void)
 {
+	if (!hvc_dcc_check())
+		return -ENODEV;
+
 	hvc_instantiate(0, 0, &hvc_dcc_get_put_ops);
 	return 0;
 }
@@ -100,6 +118,9 @@ console_initcall(hvc_dcc_console_init);
 
 static int __init hvc_dcc_init(void)
 {
+	if (!hvc_dcc_check())
+		return -ENODEV;
+
 	hvc_alloc(0, 0, &hvc_dcc_get_put_ops, 128);
 	return 0;
 }
diff --git a/drivers/tty/hvc/hvc_vio.c b/drivers/tty/hvc/hvc_vio.c
index c791b18..b594abf 100644
--- a/drivers/tty/hvc/hvc_vio.c
+++ b/drivers/tty/hvc/hvc_vio.c
@@ -48,6 +48,7 @@
 #include <asm/prom.h>
 #include <asm/hvsi.h>
 #include <asm/udbg.h>
+#include <asm/machdep.h>
 
 #include "hvc_console.h"
 
@@ -457,7 +458,9 @@ void __init hvc_vio_init_early(void)
 	if (hvterm_priv0.proto == HV_PROTOCOL_HVSI)
 		goto out;
 #endif
-	add_preferred_console("hvc", 0, NULL);
+	/* Check whether the user has requested a different console. */
+	if (!strstr(cmd_line, "console="))
+		add_preferred_console("hvc", 0, NULL);
 	hvc_instantiate(0, 0, ops);
 out:
 	of_node_put(stdout_node);