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>
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
---

Notes:
    [v4] this is new in v4 -- extracted as a separate change

 drivers/tty/serial/altera_uart.c | 6 ++----
 1 file changed, 2 insertions(+), 4 deletions(-)

diff --git a/drivers/tty/serial/altera_uart.c b/drivers/tty/serial/altera_uart.c
index a38db2cb8dc1..4170e66601ec 100644
--- 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)
-- 
2.37.3

On 2022-09-20 at 07:20:42 +0200, Jiri Slaby <jslaby@suse.cz> wrote:
> 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>
> Signed-off-by: Jiri Slaby <jslaby@suse.cz>

Acked-by: Tobias Klauser <tklauser@distanz.ch>

On Tue, 20 Sep 2022, Jiri Slaby wrote:

> 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>
> Signed-off-by: Jiri Slaby <jslaby@suse.cz>

Reviewed-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>

-- 
 i.