serial: samsung_tty: do not unlock port->lock for uart_write_wakeup()

The commit c15c374 (serial: samsung: fix potential soft lockup
during uart write) added an unlock of port->lock before
uart_write_wakeup() and a lock after it. It was always problematic to
write data from tty_ldisc_ops::write_wakeup and it was even documented
that way. We fixed the line disciplines to conform to this recently.
So if there is still a missed one, we should fix them instead of this
workaround.

On the top of that, s3c24xx_serial_tx_dma_complete() in this driver
still holds the port->lock while calling uart_write_wakeup().

So revert the wrap added by the commit above.

Cc: Thomas Abraham <thomas.abraham@linaro.org>
Cc: Kyungmin Park <kyungmin.park@samsung.com>
Cc: Hyeonkook Kim <hk619.kim@samsung.com>
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Link: https://lore.kernel.org/r/20220308115153.4225-1-jslaby@suse.cz
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Author: Jiri Slaby

drivers/tty/serial/samsung_tty.c

@@ -921,11 +921,8 @@ static void s3c24xx_serial_tx_chars(struct s3c24xx_uart_port *ourport)
 		return;
 	}
 
-	if (uart_circ_chars_pending(xmit) < WAKEUP_CHARS) {
-		spin_unlock(&port->lock);
+	if (uart_circ_chars_pending(xmit) < WAKEUP_CHARS)
 		uart_write_wakeup(port);
-		spin_lock(&port->lock);
-	}
 
 	if (uart_circ_empty(xmit))
 		s3c24xx_serial_stop_tx(port);