linux-kernel - [PATCH V2 1/2] tty: serial: imx: Only configure the wake register when device is set as wakeup source

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Message-Id: <20250924031550.2516704-2-sherry.sun@nxp.com>
Date: Wed, 24 Sep 2025 11:15:49 +0800
From: Sherry Sun <sherry.sun@....com>
To: gregkh@...uxfoundation.org,
	jirislaby@...nel.org,
	shawnguo@...nel.org,
	s.hauer@...gutronix.de,
	kernel@...gutronix.de,
	festevam@...il.com,
	shenwei.wang@....com,
	peng.fan@....com,
	frank.li@....com
Cc: linux-serial@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	imx@...ts.linux.dev
Subject: [PATCH V2 1/2] tty: serial: imx: Only configure the wake register when device is set as wakeup source

Currently, the i.MX UART driver enables wake-related registers for all
UART devices by default. However, this is unnecessary for devices that
are not configured as wakeup sources. To address this, add a
device_may_wakeup() check before configuring the UART wake-related
registers.

Fixes: db1a9b55004c ("tty: serial: imx: Allow UART to be a source for wakeup")
Signed-off-by: Sherry Sun <sherry.sun@....com>
---
 drivers/tty/serial/imx.c | 15 +++++++++++++++
 1 file changed, 15 insertions(+)

diff --git a/drivers/tty/serial/imx.c b/drivers/tty/serial/imx.c
index 500dfc009d03..87d841c0b22f 100644
--- a/drivers/tty/serial/imx.c
+++ b/drivers/tty/serial/imx.c
@@ -2697,8 +2697,23 @@ static void imx_uart_save_context(struct imx_port *sport)
 /* called with irq off */
 static void imx_uart_enable_wakeup(struct imx_port *sport, bool on)
 {
+	struct tty_port *port = &sport->port.state->port;
+	struct tty_struct *tty;
+	struct device *tty_dev;
+	bool may_wake = false;
 	u32 ucr3;
 
+	tty = tty_port_tty_get(port);
+	if (tty) {
+		tty_dev = tty->dev;
+		may_wake = tty_dev && device_may_wakeup(tty_dev);
+		tty_kref_put(tty);
+	}
+
+	/* only configure the wake register when device set as wakeup source */
+	if (!may_wake)
+		return;
+
 	uart_port_lock_irq(&sport->port);
 
 	ucr3 = imx_uart_readl(sport, UCR3);
-- 
2.34.1