[SERIAL] Add comment about frobbing the 950's ACR on TX disable.

Add a bit of explaination why we only turn off the transmitter if
we are called from uart_stop().

diff --git a/drivers/serial/8250.c b/drivers/serial/8250.c
index 7e63a7fe645ff1aa0cbe4bdb9edcbb25ad6430a4..09b3be12c248bf331453589b07272f57112dd9af 100644 (file)
--- a/drivers/serial/8250.c
+++ b/drivers/serial/8250.c
@@ -908,6 +908,12 @@ static void serial8250_stop_tx(struct uart_port *port, unsigned int tty_stop)
                up->ier &= ~UART_IER_THRI;
                serial_out(up, UART_IER, up->ier);
        }
+
+       /*
+        * We only do this from uart_stop - if we run out of
+        * characters to send, we don't want to prevent the
+        * FIFO from emptying.
+        */
        if (up->port.type == PORT_16C950 && tty_stop) {
                up->acr |= UART_ACR_TXDIS;
                serial_icr_write(up, UART_ACR, up->acr);