linux-kernel - Re: [PATCH V2 3/3] tty: serial: qcom_geni

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Date:   Mon, 17 Aug 2020 10:42:22 -0700
From:   Matthias Kaehlcke <mka@...omium.org>
To:     satya priya <skakit@...eaurora.org>
Cc:     Bjorn Andersson <bjorn.andersson@...aro.org>,
        gregkh@...uxfoundation.org, Andy Gross <agross@...nel.org>,
        Rob Herring <robh+dt@...nel.org>,
        linux-arm-msm@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, akashast@...eaurora.org,
        rojay@...eaurora.org, msavaliy@....qualcomm.com
Subject: Re: [PATCH V2 3/3] tty: serial: qcom_geni_serial: Fix the UART
 wakeup issue

On Fri, Jul 24, 2020 at 09:28:02AM +0530, satya priya wrote:
> As a part of system suspend we call uart_port_suspend from the
> Serial driver, which calls set_mctrl passing mctrl as NULL. This
> makes RFR high(NOT_READY) during suspend.
> 
> Due to this BT SoC is not able to send wakeup bytes to UART during
> suspend. Included if check for non-suspend case to keep RFR low
> during suspend.
> 
> Signed-off-by: satya priya <skakit@...eaurora.org>
> ---
> Changes in V2:
>  - This patch fixes the UART flow control issue during suspend.
>    Newly added in V2.
> 
>  drivers/tty/serial/qcom_geni_serial.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/tty/serial/qcom_geni_serial.c b/drivers/tty/serial/qcom_geni_serial.c
> index 07b7b6b..7108dfc 100644
> --- a/drivers/tty/serial/qcom_geni_serial.c
> +++ b/drivers/tty/serial/qcom_geni_serial.c
> @@ -242,7 +242,7 @@ static void qcom_geni_serial_set_mctrl(struct uart_port *uport,
>  	if (mctrl & TIOCM_LOOP)
>  		port->loopback = RX_TX_CTS_RTS_SORTED;
>  
> -	if (!(mctrl & TIOCM_RTS))
> +	if ((!(mctrl & TIOCM_RTS)) && (!(uport->suspended)))

Why all these parentheses, instead of:

    	if (!(mctrl & TIOCM_RTS) && !uport->suspended)

?