[PATCH 4/6] serial: 8250: Implement prep_tx for power management
From: Tony Lindgren <tony@atomide.com>
Date: 2021-09-21 10:34:11
Also in:
linux-omap, lkml
Subsystem:
8250/16?50 (and clone uarts) serial driver, the rest, tty layer and serial drivers · Maintainers:
Greg Kroah-Hartman, Linus Torvalds, Jiri Slaby
We can use the prep_tx() call to wake up an idle serial port. This allows ust to remove the depedency to pm_runtime_irq_safe() for 8250_omap driver in the following patches. Signed-off-by: Tony Lindgren <tony@atomide.com> --- drivers/tty/serial/8250/8250_port.c | 24 ++++++++++++++++++++++++ 1 file changed, 24 insertions(+)
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@@ -1650,6 +1650,29 @@ static enum hrtimer_restart serial8250_em485_handle_start_tx(struct hrtimer *t) return HRTIMER_NORESTART; } +static int serial8250_prep_tx(struct uart_port *port) +{ + struct uart_8250_port *up = up_to_u8250p(port); + struct device *dev = up->port.dev; + int err; + + if (!(up->capabilities & UART_CAP_RPM)) + return 0; + + if (!pm_runtime_suspended(dev)) { + pm_runtime_mark_last_busy(dev); + return 0; + } + + err = pm_request_resume(dev); + if (err < 0) { + dev_warn(dev, "prep_tx wakeup failed: %d\n", err); + return err; + } + + return -EINPROGRESS; +} + static void serial8250_start_tx(struct uart_port *port) { struct uart_8250_port *up = up_to_u8250p(port);
@@ -3227,6 +3250,7 @@ static const struct uart_ops serial8250_pops = { .set_mctrl = serial8250_set_mctrl, .get_mctrl = serial8250_get_mctrl, .stop_tx = serial8250_stop_tx, + .prep_tx = serial8250_prep_tx, .start_tx = serial8250_start_tx, .throttle = serial8250_throttle, .unthrottle = serial8250_unthrottle,
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2.33.0