From: Tony Lindgren <tony@atomide.com>
To: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Andy Shevchenko <andriy.shevchenko@intel.com>,
Jiri Slaby <jirislaby@kernel.org>,
Johan Hovold <johan@kernel.org>,
Vignesh Raghavendra <vigneshr@ti.com>,
linux-serial@vger.kernel.org, linux-omap@vger.kernel.org,
linux-kernel@vger.kernel.org
Subject: [PATCH 3/6] serial: core: Add new prep_tx for power management
Date: Tue, 21 Sep 2021 13:33:43 +0300 [thread overview]
Message-ID: <20210921103346.64824-4-tony@atomide.com> (raw)
In-Reply-To: <20210921103346.64824-1-tony@atomide.com>
If the serial driver implements PM runtime with autosuspend, the port may
be powered off for TX. To wake up the port, let's add new prep_tx() call
for serial drivers to implement as needed. We call it from serial
write_room() and write() functions. If the serial port is not enabled,
we just return 0.
Signed-off-by: Tony Lindgren <tony@atomide.com>
---
Documentation/driver-api/serial/driver.rst | 9 +++++++++
drivers/tty/serial/serial_core.c | 23 ++++++++++++++++++++++
include/linux/serial_core.h | 1 +
3 files changed, 33 insertions(+)
diff --git a/Documentation/driver-api/serial/driver.rst b/Documentation/driver-api/serial/driver.rst
--- a/Documentation/driver-api/serial/driver.rst
+++ b/Documentation/driver-api/serial/driver.rst
@@ -136,6 +136,15 @@ hardware.
This call must not sleep
+ prep_tx(port)
+ Prepare port for transmitting characters.
+
+ Locking: port->lock taken.
+
+ Interrupts: locally disabled.
+
+ This call must not sleep
+
start_tx(port)
Start transmitting characters.
diff --git a/drivers/tty/serial/serial_core.c b/drivers/tty/serial/serial_core.c
--- a/drivers/tty/serial/serial_core.c
+++ b/drivers/tty/serial/serial_core.c
@@ -118,6 +118,17 @@ static void uart_stop(struct tty_struct *tty)
uart_port_unlock(port, flags);
}
+static int __uart_prep_tx(struct tty_struct *tty)
+{
+ struct uart_state *state = tty->driver_data;
+ struct uart_port *port = state->uart_port;
+
+ if (port && !uart_tx_stopped(port) && port->ops->prep_tx)
+ return port->ops->prep_tx(port);
+
+ return 0;
+}
+
static void __uart_start(struct tty_struct *tty)
{
struct uart_state *state = tty->driver_data;
@@ -574,6 +585,12 @@ static int uart_write(struct tty_struct *tty,
return 0;
}
+ ret = __uart_prep_tx(tty);
+ if (ret < 0) {
+ uart_port_unlock(port, flags);
+ return 0;
+ }
+
while (port) {
c = CIRC_SPACE_TO_END(circ->head, circ->tail, UART_XMIT_SIZE);
if (count < c)
@@ -600,6 +617,12 @@ static unsigned int uart_write_room(struct tty_struct *tty)
unsigned int ret;
port = uart_port_lock(state, flags);
+ ret = __uart_prep_tx(tty);
+ if (ret < 0) {
+ uart_port_unlock(port, flags);
+ return 0;
+ }
+
ret = uart_circ_chars_free(&state->xmit);
uart_port_unlock(port, flags);
return ret;
diff --git a/include/linux/serial_core.h b/include/linux/serial_core.h
--- a/include/linux/serial_core.h
+++ b/include/linux/serial_core.h
@@ -40,6 +40,7 @@ struct uart_ops {
void (*set_mctrl)(struct uart_port *, unsigned int mctrl);
unsigned int (*get_mctrl)(struct uart_port *);
void (*stop_tx)(struct uart_port *);
+ int (*prep_tx)(struct uart_port *);
void (*start_tx)(struct uart_port *);
void (*throttle)(struct uart_port *);
void (*unthrottle)(struct uart_port *);
--
2.33.0
next prev parent reply other threads:[~2021-09-21 10:34 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-09-21 10:33 [PATCH 0/6] Get rid of pm_runtime_irq_safe() for 8250_omap Tony Lindgren
2021-09-21 10:33 ` [PATCH 1/6] n_tty: Start making use of -EAGAIN returned from process_output_block() Tony Lindgren
2021-09-21 11:58 ` Andy Shevchenko
2021-09-21 10:33 ` [PATCH 2/6] tty: n_gsm: Don't ignore write return value in gsmld_output() Tony Lindgren
2021-09-21 10:33 ` Tony Lindgren [this message]
2021-09-23 12:45 ` [PATCH 3/6] serial: core: Add new prep_tx for power management Johan Hovold
2021-09-23 15:02 ` Tony Lindgren
2021-09-24 14:37 ` Johan Hovold
2021-09-24 15:09 ` Tony Lindgren
2021-09-27 14:05 ` Johan Hovold
2021-09-21 10:33 ` [PATCH 4/6] serial: 8250: Implement " Tony Lindgren
2021-09-23 12:49 ` Johan Hovold
2021-09-23 15:05 ` Tony Lindgren
2021-09-24 14:44 ` Johan Hovold
2021-09-24 15:16 ` Tony Lindgren
2021-09-21 10:33 ` [PATCH 5/6] serial: 8250_omap: Require a valid wakeirq for deeper idle states Tony Lindgren
2021-09-21 10:33 ` [PATCH 6/6] serial: 8250_omap: Drop the use of pm_runtime_irq_safe() Tony Lindgren
2021-09-21 12:03 ` [PATCH 0/6] Get rid of pm_runtime_irq_safe() for 8250_omap Andy Shevchenko
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