tty: serial: clean up stop-tx part in altera_uart_tx_chars()

[ Upstream commit d9c128117da41cf4cb0e80ae565b5d3ac79dffac ]

The "stop TX" path in altera_uart_tx_chars() is open-coded, so:
* use uart_circ_empty() to check if the buffer is empty, and
* when true, call altera_uart_stop_tx().

Cc: Tobias Klauser <tklauser@distanz.ch>
Reviewed-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Acked-by: Tobias Klauser <tklauser@distanz.ch>
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Link: https://lore.kernel.org/r/20220920052049.20507-3-jslaby@suse.cz
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Stable-dep-of: 1307c5d33cce ("serial: altera_uart: fix locking in polling mode")
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/drivers/tty/serial/altera_uart.c b/drivers/tty/serial/altera_uart.c
index 7c5f4e9..0e19455 100644 (file)
--- a/drivers/tty/serial/altera_uart.c
+++ b/drivers/tty/serial/altera_uart.c
@@ -272,10 +272,8 @@ static void altera_uart_tx_chars(struct altera_uart *pp)
        if (uart_circ_chars_pending(xmit) < WAKEUP_CHARS)
                uart_write_wakeup(port);
 
-       if (xmit->head == xmit->tail) {
-               pp->imr &= ~ALTERA_UART_CONTROL_TRDY_MSK;
-               altera_uart_update_ctrl_reg(pp);
-       }
+       if (uart_circ_empty(xmit))
+               altera_uart_stop_tx(port);
 }
 
 static irqreturn_t altera_uart_interrupt(int irq, void *data)