USB: ti_usb_3410_5052: 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 2c992cd73 ("USB:
ti_usb_3410_5052: 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, 15 insertions, 8 deletions

diff --git a/drivers/usb/serial/ti_usb_3410_5052.c b/drivers/usb/serial/ti_usb_3410_5052.c
index cac47aef2918..c92c5ed4e580 100644
--- a/drivers/usb/serial/ti_usb_3410_5052.c
+++ b/drivers/usb/serial/ti_usb_3410_5052.c
@@ -101,6 +101,7 @@ static int ti_write(struct tty_struct *tty, struct usb_serial_port *port,
                 const unsigned char *data, int count);
 static int ti_write_room(struct tty_struct *tty);
 static int ti_chars_in_buffer(struct tty_struct *tty);
+static bool ti_tx_empty(struct usb_serial_port *port);
 static void ti_throttle(struct tty_struct *tty);
 static void ti_unthrottle(struct tty_struct *tty);
 static int ti_ioctl(struct tty_struct *tty,
@@ -222,6 +223,7 @@ static struct usb_serial_driver ti_1port_device = {
         .write                  = ti_write,
         .write_room             = ti_write_room,
         .chars_in_buffer        = ti_chars_in_buffer,
+        .tx_empty               = ti_tx_empty,
         .throttle               = ti_throttle,
         .unthrottle             = ti_unthrottle,
         .ioctl                  = ti_ioctl,
@@ -253,6 +255,7 @@ static struct usb_serial_driver ti_2port_device = {
         .write                  = ti_write,
         .write_room             = ti_write_room,
         .chars_in_buffer        = ti_chars_in_buffer,
+        .tx_empty               = ti_tx_empty,
         .throttle               = ti_throttle,
         .unthrottle             = ti_unthrottle,
         .ioctl                  = ti_ioctl,
@@ -684,8 +687,6 @@ 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;
@@ -694,16 +695,22 @@ 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;
 }
 
+static bool ti_tx_empty(struct usb_serial_port *port)
+{
+        struct ti_port *tport = usb_get_serial_port_data(port);
+        int ret;
+        u8 lsr;
+
+        ret = ti_get_lsr(tport, &lsr);
+        if (!ret && !(lsr & TI_LSR_TX_EMPTY))
+                return false;
+
+        return true;
+}
 
 static void ti_throttle(struct tty_struct *tty)
 {