X-Git-Url: http://demsky.eecs.uci.edu/git/?a=blobdiff_plain;f=drivers%2Ftty%2Fhvc%2Fhvc_dcc.c;h=3502a7bbb69eee716f21b5b5b89c14fd3f9627fb;hb=0a759b2466d19c619257fec36f988f93424cf3ae;hp=44fbebab5075f98f337d880288993b01ad9e7271;hpb=986836503e49ccf7e84b813715d344964ec93566;p=firefly-linux-kernel-4.4.55.git

diff --git a/drivers/tty/hvc/hvc_dcc.c b/drivers/tty/hvc/hvc_dcc.c
index 44fbebab5075..3502a7bbb69e 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;
 }