linux-kernel - Re: [PATCH V2 2/3] tty: serial: fsl_lpuart: remove RTS/CTS control from set/get

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Message-ID: <20150608064113.GX18985@pengutronix.de>
Date:	Mon, 8 Jun 2015 08:41:13 +0200
From:	Uwe Kleine-König 
	<u.kleine-koenig@...gutronix.de>
To:	Bhuvanchandra DV <bhuvanchandra.dv@...adex.com>
Cc:	gregkh@...uxfoundation.org, devicetree@...r.kernel.org,
	linux-serial@...r.kernel.org, moorray3@...pl,
	linux-kernel@...r.kernel.org, stefan@...er.ch,
	bhuvanchandra.dv@...il.com, kernel@...gutronix.de,
	shawn.guo@...aro.org, jslaby@...e.cz,
	linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH V2 2/3] tty: serial: fsl_lpuart: remove RTS/CTS control
 from set/get_mctrl

Hello,

On Mon, Jun 01, 2015 at 10:51:06AM +0530, Bhuvanchandra DV wrote:
> The LPUART does not provide manual control of RTS/CTS signals,
> those can only be controlled by the hardware directly. Therefore
> manual control of those signals through mctrl can not be provided.
> The current implementation enables/disables the automatic control,
> which is not what mctrl should do, hence remove the incorrect
> implementation.
> 
> Signed-off-by: Bhuvanchandra DV <bhuvanchandra.dv@...adex.com>
> ---
>  drivers/tty/serial/fsl_lpuart.c | 63 +++++------------------------------------
>  1 file changed, 7 insertions(+), 56 deletions(-)
> 
> diff --git a/drivers/tty/serial/fsl_lpuart.c b/drivers/tty/serial/fsl_lpuart.c
> index 08ce76f..532cfb7 100644
> --- a/drivers/tty/serial/fsl_lpuart.c
> +++ b/drivers/tty/serial/fsl_lpuart.c
> @@ -822,64 +822,15 @@ static unsigned int lpuart32_tx_empty(struct uart_port *port)
>  
>  static unsigned int lpuart_get_mctrl(struct uart_port *port)
>  {
> -	unsigned int temp = 0;
> -	unsigned char reg;
> -
> -	reg = readb(port->membase + UARTMODEM);
> -	if (reg & UARTMODEM_TXCTSE)
> -		temp |= TIOCM_CTS;
> -
> -	if (reg & UARTMODEM_RXRTSE)
> -		temp |= TIOCM_RTS;
> -
> -	return temp;
>From reading the commit log I would expect that you only touch the
set_mctrl function, but not get_mctrl. Assuming your code change is
right, can you mention this in the commit log please? The bits
UARTMODEM_TXCTSE and UARTMODEM_RXRTSE only control the automatic mode?

What is the problem you're fixing here? I'm not sure how such an UART
should be handled, but I imagine that you want to make use of automatic
mode in some cases. Greg?

Best regards
Uwe

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