--- drivers/usb/serial/ch341.c

+++ drivers/usb/serial/ch341.c

@@ -479,12 +479,22 @@ static void ch341_read_int_callback(stru

if (actual_length >= 4) {

struct ch341_private *priv = usb_get_serial_port_data(port);

unsigned long flags;

+ u8 prev_line_status = priv->line_status;

spin_lock_irqsave(&priv->lock, flags);

priv->line_status = (~(data[2])) & CH341_BITS_MODEM_STAT;

if ((data[1] & CH341_MULT_STAT))

priv->multi_status_change = 1;

spin_unlock_irqrestore(&priv->lock, flags);

+

+ if ((priv->line_status ^ prev_line_status) & CH341_BIT_DCD) {

+ struct tty_struct *tty = tty_port_tty_get(&port->port);

+ if (tty)

+ usb_serial_handle_dcd_change(port, tty,

+ priv->line_status & CH341_BIT_DCD);

+ tty_kref_put(tty);

+ }

+

wake_up_interruptible(&priv->delta_msr_wait);

}