linux-kernel - Re: [PATCH] serial: core: Do stop_rx in suspend path for console if console

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Message-ID: <0eedc244-5c8a-c734-8bba-09a66d050a4e@quicinc.com>
Date:   Mon, 16 May 2022 14:55:50 +0530
From:   Vijaya Krishna Nivarthi <quic_vnivarth@...cinc.com>
To:     <gregkh@...uxfoundation.org>, <jirislaby@...nel.org>,
        <linux-serial@...r.kernel.org>, <linux-kernel@...r.kernel.org>
CC:     <quic_msavaliy@...cinc.com>, <dianders@...omium.org>
Subject: Re: [PATCH] serial: core: Do stop_rx in suspend path for console if
 console_suspend is disabled

This patch will be dropped.

Uploaded this change as v4 of an earlier patch.
Apologies for trouble.

On 5/2/2022 3:17 PM, Vijaya Krishna Nivarthi wrote:
> For the case of console_suspend disabled, if back to back suspend/resume
> test is executed, at the end of test, sometimes console would appear to
> be frozen not responding to input. This would happen because, during
> resume, rx transactions can come in before system is ready, malfunction
> of rx happens in turn resulting in console appearing to be stuck.
>
> Do a stop_rx in suspend sequence to prevent this.
>
> Signed-off-by: Vijaya Krishna Nivarthi <quic_vnivarth@...cinc.com>
> ---
>   drivers/tty/serial/serial_core.c | 11 +++++++++--
>   1 file changed, 9 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/tty/serial/serial_core.c b/drivers/tty/serial/serial_core.c
> index 82a1770..e8c6875 100644
> --- a/drivers/tty/serial/serial_core.c
> +++ b/drivers/tty/serial/serial_core.c
> @@ -2211,9 +2211,16 @@ int uart_suspend_port(struct uart_driver *drv, struct uart_port *uport)
>   	}
>   	put_device(tty_dev);
>   
> -	/* Nothing to do if the console is not suspending */
> -	if (!console_suspend_enabled && uart_console(uport))
> +	/*
> +	 * Nothing to do if the console is not suspending
> +	 * except stop_rx to prevent any asynchronous data
> +	 * over RX line. Re start_rx, when required, is
> +	 * done by set_termios in resume sequence
> +	 */
> +	if (!console_suspend_enabled && uart_console(uport)) {
> +		uport->ops->stop_rx(uport);
>   		goto unlock;
> +	}
>   
>   	uport->suspended = 1;
>