[PATCH v1 3/3] serial: fsl_lpuart: Enable TTY wakeup for wakeup-source ports

[Stefano Radaelli <stefano.radaelli21@gmail.com>]

From: Stefano Radaelli <stefano.r@variscite.com>

LPUART checks the TTY wakeup policy when preparing a port for system
suspend, but does not currently use the wakeup-source DT property.
Consequently, userspace must enable TTY wakeup even for ports marked as
wakeup sources.

Set tty_wakeup_default from wakeup-source before registering the port.
For TTY ports with the property, the serial core then enables wakeup at
registration. Ports without it keep the existing default, and userspace
can still disable wakeup through power/wakeup. The port must still be
open and initialized for receive activity to wake the system.

Tested on a Variscite VAR-SOM-MX93 with a Symphony carrier board using
LPUART1 (ttyLP0) as the console. With wakeup-source present, power/wakeup
was enabled after boot without a userspace write. After requesting deep
suspend, the board stayed suspended until Enter was pressed on the serial
console, then resumed.

Signed-off-by: Stefano Radaelli <stefano.r@variscite.com>
---
 drivers/tty/serial/fsl_lpuart.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/tty/serial/fsl_lpuart.c b/drivers/tty/serial/fsl_lpuart.c
index c8575c965203..35397152a39b 100644
--- a/drivers/tty/serial/fsl_lpuart.c
+++ b/drivers/tty/serial/fsl_lpuart.c
@@ -2905,6 +2905,7 @@ static int lpuart_probe(struct platform_device *pdev)
 		sport->port.ops = &lpuart_pops;
 	sport->port.has_sysrq = IS_ENABLED(CONFIG_SERIAL_FSL_LPUART_CONSOLE);
 	sport->port.flags = UPF_BOOT_AUTOCONF;
+	sport->port.tty_wakeup_default = of_property_read_bool(np, "wakeup-source");
 
 	if (lpuart_is_32(sport))
 		sport->port.rs485_config = lpuart32_config_rs485;
-- 
2.47.3