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

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Message-ID: <20250923083208.GC31170@nxa18884-linux.ap.freescale.net>
Date: Tue, 23 Sep 2025 16:32:08 +0800
From: Peng Fan <peng.fan@....nxp.com>
To: Sherry Sun <sherry.sun@....com>
Cc: gregkh@...uxfoundation.org, jirislaby@...nel.org, shawnguo@...nel.org,
	s.hauer@...gutronix.de, kernel@...gutronix.de, festevam@...il.com,
	shenwei.wang@....com, linux-serial@...r.kernel.org,
	linux-kernel@...r.kernel.org, imx@...ts.linux.dev
Subject: Re: [PATCH 1/2] tty: serial: imx: Only configure the wake register
 when device is set as wakeup source

On Tue, Sep 23, 2025 at 11:16:12AM +0800, Sherry Sun wrote:
>Currently, imx uart defaults to enabling the wake related registers for
>all uart devices. However, it is unnecessary for those devices not
>configured as wakeup source, so add device_may_wakeup() check before
>configuring the uart wake related registers.

I would rewrite as this:
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..4ddfc89816bf 100644
>--- a/drivers/tty/serial/imx.c
>+++ b/drivers/tty/serial/imx.c
>@@ -2697,7 +2697,22 @@ 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;
> 	u32 ucr3;
>+	bool may_wake;

'bool may_wake = false;' otherwise there might be report on using an
uninitalized value by coverity or other tools.

>+
>+	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;

Regards,
Peng