| Message ID | 20220411094805.45696-2-tony@atomide.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | [1/2] serial: 8250: Fix runtime PM for start_tx() for RS485 | expand |
On Mon, Apr 11, 2022 at 12:48:05PM +0300, Tony Lindgren wrote: > Commit 932d596378b0 ("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. > > We need to call serial8250_rpm_put_tx() on early exit, it normally gets > called later on at __stop_tx(). > > Fixes: 932d596378b0 ("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> > Signed-off-by: Tony Lindgren <tony@atomide.com> > --- > drivers/tty/serial/8250/8250_port.c | 4 +++- > 1 file changed, 3 insertions(+), 1 deletion(-) > > diff --git a/drivers/tty/serial/8250/8250_port.c b/drivers/tty/serial/8250/8250_port.c > --- a/drivers/tty/serial/8250/8250_port.c > +++ b/drivers/tty/serial/8250/8250_port.c > @@ -1677,8 +1677,10 @@ static void serial8250_start_tx(struct uart_port *port) > > serial8250_rpm_get_tx(up); > > - if (!port->x_char && uart_circ_empty(&port->state->xmit)) > + if (!port->x_char && uart_circ_empty(&port->state->xmit)) { > + serial8250_rpm_put_tx(up); > return; > + } Assuming you don't need serial8250_rpm_get_tx() to check the condition, it would be easier to move the early return before the call to serial8250_rpm_get_tx(). Best regards Uwe
* Uwe Kleine-König <u.kleine-koenig@pengutronix.de> [220411 09:59]: > On Mon, Apr 11, 2022 at 12:48:05PM +0300, Tony Lindgren wrote: > > Commit 932d596378b0 ("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. > > > > We need to call serial8250_rpm_put_tx() on early exit, it normally gets > > called later on at __stop_tx(). > > > > Fixes: 932d596378b0 ("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> > > Signed-off-by: Tony Lindgren <tony@atomide.com> > > --- > > drivers/tty/serial/8250/8250_port.c | 4 +++- > > 1 file changed, 3 insertions(+), 1 deletion(-) > > > > diff --git a/drivers/tty/serial/8250/8250_port.c b/drivers/tty/serial/8250/8250_port.c > > --- a/drivers/tty/serial/8250/8250_port.c > > +++ b/drivers/tty/serial/8250/8250_port.c > > @@ -1677,8 +1677,10 @@ static void serial8250_start_tx(struct uart_port *port) > > > > serial8250_rpm_get_tx(up); > > > > - if (!port->x_char && uart_circ_empty(&port->state->xmit)) > > + if (!port->x_char && uart_circ_empty(&port->state->xmit)) { > > + serial8250_rpm_put_tx(up); > > return; > > + } > > Assuming you don't need serial8250_rpm_get_tx() to check the condition, > it would be easier to move the early return before the call to > serial8250_rpm_get_tx(). Yeah good suggestion, that should work. Regards, Tony
On Mon, Apr 11, 2022 at 12:48:05PM +0300, Tony Lindgren wrote: > Commit 932d596378b0 ("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. > > We need to call serial8250_rpm_put_tx() on early exit, it normally gets > called later on at __stop_tx(). > > Fixes: 932d596378b0 ("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> > Signed-off-by: Tony Lindgren <tony@atomide.com> > --- > drivers/tty/serial/8250/8250_port.c | 4 +++- > 1 file changed, 3 insertions(+), 1 deletion(-) > > diff --git a/drivers/tty/serial/8250/8250_port.c b/drivers/tty/serial/8250/8250_port.c > --- a/drivers/tty/serial/8250/8250_port.c > +++ b/drivers/tty/serial/8250/8250_port.c > @@ -1677,8 +1677,10 @@ static void serial8250_start_tx(struct uart_port *port) > > serial8250_rpm_get_tx(up); > > - if (!port->x_char && uart_circ_empty(&port->state->xmit)) > + if (!port->x_char && uart_circ_empty(&port->state->xmit)) { > + serial8250_rpm_put_tx(up); > return; > + } Move this before the runtime pm get instead? > > if (em485 && > em485->active_timer == &em485->start_tx_timer) { Johan
* Johan Hovold <johan@kernel.org> [220411 10:10]: > On Mon, Apr 11, 2022 at 12:48:05PM +0300, Tony Lindgren wrote: > > diff --git a/drivers/tty/serial/8250/8250_port.c b/drivers/tty/serial/8250/8250_port.c > > --- a/drivers/tty/serial/8250/8250_port.c > > +++ b/drivers/tty/serial/8250/8250_port.c > > @@ -1677,8 +1677,10 @@ static void serial8250_start_tx(struct uart_port *port) > > > > serial8250_rpm_get_tx(up); > > > > - if (!port->x_char && uart_circ_empty(&port->state->xmit)) > > + if (!port->x_char && uart_circ_empty(&port->state->xmit)) { > > + serial8250_rpm_put_tx(up); > > return; > > + } > > Move this before the runtime pm get instead? Yup good idea. Tony
diff --git a/drivers/tty/serial/8250/8250_port.c b/drivers/tty/serial/8250/8250_port.c --- a/drivers/tty/serial/8250/8250_port.c +++ b/drivers/tty/serial/8250/8250_port.c @@ -1677,8 +1677,10 @@ static void serial8250_start_tx(struct uart_port *port) serial8250_rpm_get_tx(up); - if (!port->x_char && uart_circ_empty(&port->state->xmit)) + if (!port->x_char && uart_circ_empty(&port->state->xmit)) { + serial8250_rpm_put_tx(up); return; + } if (em485 && em485->active_timer == &em485->start_tx_timer) {
Commit 932d596378b0 ("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. We need to call serial8250_rpm_put_tx() on early exit, it normally gets called later on at __stop_tx(). Fixes: 932d596378b0 ("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> Signed-off-by: Tony Lindgren <tony@atomide.com> --- drivers/tty/serial/8250/8250_port.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-)