linux-kernel - Re: [V3] drivers/tty/serial/qcom-geni-serial: Do stop_rx in suspend path for console if console

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Date:   Thu, 7 Apr 2022 09:51:50 +0200
From:   Jiri Slaby <jirislaby@...nel.org>
To:     Vijaya Krishna Nivarthi <quic_vnivarth@...cinc.com>,
        agross@...nel.org, bjorn.andersson@...aro.org,
        gregkh@...uxfoundation.org, linux-arm-msm@...r.kernel.org,
        linux-serial@...r.kernel.org, linux-kernel@...r.kernel.org
Cc:     quic_msavaliy@...cinc.com, dianders@...omium.org
Subject: Re: [V3] drivers/tty/serial/qcom-geni-serial: Do stop_rx in suspend
 path for console if console_suspend is disabled

On 07. 04. 22, 9:25, 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, for
> console_suspend disabled, suspend/resume routines only turn resources
> off/on but don't do a port close/open.
> As a result, during resume, some rx transactions 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. start_rx is already
> present in resume sequence as part of call to set_termios which does a
> stop_rx/start_rx.

So why is it OK for every other driver? Should uart_suspend_port() be 
fixed instead?

> Signed-off-by: Vijaya Krishna Nivarthi <quic_vnivarth@...cinc.com>
> ---
> v3: swapped the order of conditions to be more human readable
> v2: restricted patch to contain only stop_rx in suspend sequence
> v1: intial patch contained 2 additional unrelated changes in vicinity
> ---
>   drivers/tty/serial/qcom_geni_serial.c | 4 ++++
>   1 file changed, 4 insertions(+)
> 
> diff --git a/drivers/tty/serial/qcom_geni_serial.c b/drivers/tty/serial/qcom_geni_serial.c
> index 1543a60..53723d2 100644
> --- a/drivers/tty/serial/qcom_geni_serial.c
> +++ b/drivers/tty/serial/qcom_geni_serial.c
> @@ -1481,6 +1481,10 @@ static int __maybe_unused qcom_geni_serial_sys_suspend(struct device *dev)
>   	struct uart_port *uport = &port->uport;
>   	struct qcom_geni_private_data *private_data = uport->private_data;
>   
> +	/* do a stop_rx here, start_rx is handled in uart_resume_port by call to setermios */
> +	if (uart_console(uport) && !console_suspend_enabled)
> +		uport->ops->stop_rx(uport);
> +
>   	/*
>   	 * This is done so we can hit the lowest possible state in suspend
>   	 * even with no_console_suspend

thanks,
-- 
js
suse labs