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serial: 8250: Fix runtime PM for start_tx() for empty buffer

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Commit 932d596378 ("serial: 8250: Return early in .start_tx() if there
are no chars to send") caused a regression where the drivers implementing
runtime PM stopped idling. This is because serial8250_rpm_put_tx() is now
unbalanced on early return, it normally gets called at __stop_tx().

Fixes: 932d596378 ("serial: 8250: Return early in .start_tx() if there are no chars to send")
Cc: Steffen Trumtrar <s.trumtrar@pengutronix.de>
Cc: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Reviewed-by: Johan Hovold <johan@kernel.org>
Reviewed-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Signed-off-by: Tony Lindgren <tony@atomide.com>
Link: https://lore.kernel.org/r/20220411111657.16744-1-tony@atomide.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Tony Lindgren
2022-04-11 14:16:57 +03:00
committed by Greg Kroah-Hartman
parent 3ee82c6e41
commit cc994bb975
1 changed files with 2 additions and 2 deletions
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4
drivers/tty/serial/8250/8250_port.c
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@@ -1675,11 +1675,11 @@ static void serial8250_start_tx(struct uart_port *port)
struct uart_8250_port *up = up_to_u8250p(port);
struct uart_8250_em485 *em485 = up->em485;
serial8250_rpm_get_tx(up);
if (!port->x_char && uart_circ_empty(&port->state->xmit))
return;
serial8250_rpm_get_tx(up);
if (em485 &&
em485->active_timer == &em485->start_tx_timer)
return;