linux-kernel - Re: [PATCH V3 1/2] tty: serial: imx: Only configure the wake register when device is set as wakeup source

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Message-ID: <9b603e71-c0a1-46f3-93f2-dd31188dbeff@kernel.org>
Date: Mon, 29 Sep 2025 07:54:17 +0200
From: Jiri Slaby <jirislaby@...nel.org>
To: Sherry Sun <sherry.sun@....com>, gregkh@...uxfoundation.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: Re: [PATCH V3 1/2] tty: serial: imx: Only configure the wake register
 when device is set as wakeup source

On 25. 09. 25, 11:11, 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) {

Use scoped_guard(tty_port_tty, port) instead.

> +		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);

thanks,
-- 
js
suse labs