Re: [PATCH v6 2/3] serial: imx: set_mctrl(): correctly restore autoRTS state

["Uwe Kleine-König" <u.kleine-koenig@pengutronix.de>]

On Mon, Jul 22, 2019 at 10:22:10PM +0300, Sergey Organov wrote:
> imx_uart_set_mctrl() happened to set UCR2_CTSC bit whenever TIOCM_RTS
> was set, no matter if RTS/CTS handshake is enabled or not. Now fixed by
> turning handshake on only when CRTSCTS bit for the port is set.
> 
> Acked-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
> Reviewed-by: Sascha Hauer <s.hauer@pengutronix.de>
> Tested-by: Sascha Hauer <s.hauer@pengutronix.de>
> Signed-off-by: Sergey Organov <sorganov@gmail.com>
> ---
>  drivers/tty/serial/imx.c | 16 ++++++++++++++--
>  1 file changed, 14 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/tty/serial/imx.c b/drivers/tty/serial/imx.c
> index 32f36d8..059ba35 100644
> --- a/drivers/tty/serial/imx.c
> +++ b/drivers/tty/serial/imx.c
> @@ -974,10 +974,22 @@ static void imx_uart_set_mctrl(struct uart_port *port, unsigned int mctrl)
>  	if (!(port->rs485.flags & SER_RS485_ENABLED)) {
>  		u32 ucr2;
>  
> +		/*
> +		 * Turn off autoRTS if RTS is lowered and restore autoRTS
> +		 * setting if RTS is raised.

"lower" and "raising" are misleading here. I recommend sticking to
"active" and "inactive".

> +		 */
>  		ucr2 = imx_uart_readl(sport, UCR2);
>  		ucr2 &= ~(UCR2_CTS | UCR2_CTSC);
> -		if (mctrl & TIOCM_RTS)
> -			ucr2 |= UCR2_CTS | UCR2_CTSC;
> +		if (mctrl & TIOCM_RTS) {
> +			ucr2 |= UCR2_CTS;
> +			/*
> +			 * UCR2_IRTS is unset if and only if the port is
> +			 * configured for CRTSCTS, so we use inverted UCR2_IRTS
> +			 * to get the state to restore to.
> +			 */
> +			if (!(ucr2 & UCR2_IRTS))
> +				ucr2 |= UCR2_CTSC;
> +		}

If you teach imx_uart_rts_auto about IRTS this function could be reused
here I think.

Best regards
Uwe

-- 
Pengutronix e.K.                           | Uwe Kleine-König            |
Industrial Linux Solutions                 | http://www.pengutronix.de/  |

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