USB: ti_usb_3410_5052: query hardware-buffer status in chars_in_buffer

Query hardware-buffer status in chars_in_buffer should the write fifo be
empty.

This is needed to make the tty layer wait for hardware buffers to drain
on close.

Signed-off-by: Johan Hovold <jhovold@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 8 insertions, 0 deletions

diff --git a/drivers/usb/serial/ti_usb_3410_5052.c b/drivers/usb/serial/ti_usb_3410_5052.c
index 3ed8ecafe597..062b6d872ea3 100644
--- a/drivers/usb/serial/ti_usb_3410_5052.c
+++ b/drivers/usb/serial/ti_usb_3410_5052.c
@@ -687,6 +687,8 @@ static int ti_chars_in_buffer(struct tty_struct *tty)
         struct ti_port *tport = usb_get_serial_port_data(port);
         int chars = 0;
         unsigned long flags;
+        int ret;
+        u8 lsr;
 
         if (tport == NULL)
                 return 0;
@@ -695,6 +697,12 @@ static int ti_chars_in_buffer(struct tty_struct *tty)
         chars = kfifo_len(&tport->write_fifo);
         spin_unlock_irqrestore(&tport->tp_lock, flags);
 
+        if (!chars) {
+                ret = ti_get_lsr(tport, &lsr);
+                if (!ret && !(lsr & TI_LSR_TX_EMPTY))
+                        chars = 1;
+        }
+
         dev_dbg(&port->dev, "%s - returns %d\n", __func__, chars);
         return chars;
 }