diff --git a/arch/powerpc/platforms/pseries/hvconsole.c b/arch/powerpc/platforms/pseries/hvconsole.c
index 74da18de853a..73ec15cd2708 100644
--- a/arch/powerpc/platforms/pseries/hvconsole.c
+++ b/arch/powerpc/platforms/pseries/hvconsole.c
@@ -62,7 +62,7 @@ EXPORT_SYMBOL(hvc_get_chars);
  * @vtermno: The vtermno or unit_address of the adapter from which the data
  *	originated.
  * @buf: The character buffer that contains the character data to send to
- *	firmware.
+ *	firmware. Must be at least 16 bytes, even if count is less than 16.
  * @count: Send this number of characters.
  */
 int hvc_put_chars(uint32_t vtermno, const char *buf, int count)
diff --git a/drivers/tty/hvc/hvc_vio.c b/drivers/tty/hvc/hvc_vio.c
index 6de6d4a1a221..7af54d6ed5b8 100644
--- a/drivers/tty/hvc/hvc_vio.c
+++ b/drivers/tty/hvc/hvc_vio.c
@@ -107,6 +107,14 @@ static int hvterm_raw_get_chars(uint32_t vtermno, char *buf, int count)
 	return got;
 }
 
+/**
+ * hvterm_raw_put_chars: send characters to firmware for given vterm adapter
+ * @vtermno: The virtual terminal number.
+ * @buf: The characters to send. Because of the underlying hypercall in
+ *       hvc_put_chars(), this buffer must be at least 16 bytes long, even if
+ *       you are sending fewer chars.
+ * @count: number of chars to send.
+ */
 static int hvterm_raw_put_chars(uint32_t vtermno, const char *buf, int count)
 {
 	struct hvterm_priv *pv = hvterm_privs[vtermno];
@@ -219,6 +227,7 @@ static const struct hv_ops hvterm_hvsi_ops = {
 static void udbg_hvc_putc(char c)
 {
 	int count = -1;
+	unsigned char bounce_buffer[16];
 
 	if (!hvterm_privs[0])
 		return;
@@ -229,7 +238,12 @@ static void udbg_hvc_putc(char c)
 	do {
 		switch(hvterm_privs[0]->proto) {
 		case HV_PROTOCOL_RAW:
-			count = hvterm_raw_put_chars(0, &c, 1);
+			/*
+			 * hvterm_raw_put_chars requires at least a 16-byte
+			 * buffer, so go via the bounce buffer
+			 */
+			bounce_buffer[0] = c;
+			count = hvterm_raw_put_chars(0, bounce_buffer, 1);
 			break;
 		case HV_PROTOCOL_HVSI:
 			count = hvterm_hvsi_put_chars(0, &c, 1);