USB: io_ti: fix chars_in_buffer overhead

Use the new generic usb-serial wait_until_sent implementation to wait
for hardware buffers to drain.

This removes the need to check the hardware buffers in chars_in_buffer
and thus removes the overhead introduced by commit 263e1f9f ("USB:
io_ti: query hardware-buffer status in chars_in_buffer") without
breaking tty_wait_until_sent (used by, for example, tcdrain, tcsendbreak
and close).

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

1 files changed, 14 insertions, 8 deletions

diff --git a/drivers/usb/serial/io_ti.c b/drivers/usb/serial/io_ti.c
index 158bf4bc29cc..1be6ba7bee27 100644
--- a/drivers/usb/serial/io_ti.c
+++ b/drivers/usb/serial/io_ti.c
@@ -2019,8 +2019,6 @@ static int edge_chars_in_buffer(struct tty_struct *tty)
         struct edgeport_port *edge_port = usb_get_serial_port_data(port);
         int chars = 0;
         unsigned long flags;
-        int ret;
-
         if (edge_port == NULL)
                 return 0;
 
@@ -2028,16 +2026,22 @@ static int edge_chars_in_buffer(struct tty_struct *tty)
         chars = kfifo_len(&edge_port->write_fifo);
         spin_unlock_irqrestore(&edge_port->ep_lock, flags);
 
-        if (!chars) {
-                ret = tx_active(edge_port);
-                if (ret > 0)
-                        chars = ret;
-        }
-
         dev_dbg(&port->dev, "%s - returns %d\n", __func__, chars);
         return chars;
 }
 
+static bool edge_tx_empty(struct usb_serial_port *port)
+{
+        struct edgeport_port *edge_port = usb_get_serial_port_data(port);
+        int ret;
+
+        ret = tx_active(edge_port);
+        if (ret > 0)
+                return false;
+
+        return true;
+}
+
 static void edge_throttle(struct tty_struct *tty)
 {
         struct usb_serial_port *port = tty->driver_data;
@@ -2557,6 +2561,7 @@ static struct usb_serial_driver edgeport_1port_device = {
         .write                  = edge_write,
         .write_room             = edge_write_room,
         .chars_in_buffer        = edge_chars_in_buffer,
+        .tx_empty               = edge_tx_empty,
         .break_ctl              = edge_break,
         .read_int_callback      = edge_interrupt_callback,
         .read_bulk_callback     = edge_bulk_in_callback,
@@ -2589,6 +2594,7 @@ static struct usb_serial_driver edgeport_2port_device = {
         .write                  = edge_write,
         .write_room             = edge_write_room,
         .chars_in_buffer        = edge_chars_in_buffer,
+        .tx_empty               = edge_tx_empty,
         .break_ctl              = edge_break,
         .read_int_callback      = edge_interrupt_callback,
         .read_bulk_callback     = edge_bulk_in_callback,