linux-kernel - Re: [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: <aNQFHJlnmn9V2Eyy@lizhi-Precision-Tower-5810>
Date: Wed, 24 Sep 2025 10:50:04 -0400
From: Frank Li <Frank.li@....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, peng.fan@....com,
	linux-serial@...r.kernel.org, linux-kernel@...r.kernel.org,
	imx@...ts.linux.dev
Subject: Re: [PATCH V2 1/2] tty: serial: imx: Only configure the wake
 register when device is set as wakeup source

On Wed, Sep 24, 2025 at 11:15:49AM +0800, Sherry Sun wrote:
> 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>
> ---
Reviewed-by: Frank Li <Frank.Li@....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
>