linux-kernel - Re: [PATCH 1/2] serial: imx: cleanup imx_uart_disable

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Date:   Tue, 8 May 2018 08:40:47 +0200
From:   Uwe Kleine-König 
        <u.kleine-koenig@...gutronix.de>
To:     Sebastian Reichel <sebastian.reichel@...labora.co.uk>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Jiri Slaby <jslaby@...e.com>, linux-serial@...r.kernel.org,
        Fabio Estevam <fabio.estevam@....com>,
        Shawn Guo <shawnguo@...nel.org>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/2] serial: imx: cleanup imx_uart_disable_dma()

Hello,

On Mon, May 07, 2018 at 11:36:09PM +0200, Sebastian Reichel wrote:
> Remove unrelated CTSC/CTS disabling from imx_uart_disable_dma() and
> move it to imx_uart_shutdown(), which is the only user of the DMA
> disabling function. This should not change the driver's behaviour,
> but improves readability. After this change imx_uart_disable_dma()
> does the reverse thing of imx_uart_enable_dma().
> 
> Suggested-by: Nandor Han <nandor.han@...com>
> Signed-off-by: Sebastian Reichel <sebastian.reichel@...labora.co.uk>
> ---
>  drivers/tty/serial/imx.c | 9 ++-------
>  1 file changed, 2 insertions(+), 7 deletions(-)
> 
> diff --git a/drivers/tty/serial/imx.c b/drivers/tty/serial/imx.c
> index c2fc6bef7a6f..3ca767b1162a 100644
> --- a/drivers/tty/serial/imx.c
> +++ b/drivers/tty/serial/imx.c
> @@ -1291,18 +1291,13 @@ static void imx_uart_enable_dma(struct imx_port *sport)
>  
>  static void imx_uart_disable_dma(struct imx_port *sport)
>  {
> -	u32 ucr1, ucr2;
> +	u32 ucr1;
>  
>  	/* clear UCR1 */
>  	ucr1 = imx_uart_readl(sport, UCR1);
>  	ucr1 &= ~(UCR1_RXDMAEN | UCR1_TXDMAEN | UCR1_ATDMAEN);
>  	imx_uart_writel(sport, ucr1, UCR1);
>  
> -	/* clear UCR2 */
> -	ucr2 = imx_uart_readl(sport, UCR2);
> -	ucr2 &= ~(UCR2_CTSC | UCR2_CTS | UCR2_ATEN);
> -	imx_uart_writel(sport, ucr2, UCR2);
> -
>  	imx_uart_setup_ufcr(sport, TXTL_DEFAULT, RXTL_DEFAULT);
>  
>  	sport->dma_is_enabled = 0;
> @@ -1447,7 +1442,7 @@ static void imx_uart_shutdown(struct uart_port *port)
>  
>  	spin_lock_irqsave(&sport->port.lock, flags);
>  	ucr2 = imx_uart_readl(sport, UCR2);
> -	ucr2 &= ~(UCR2_TXEN | UCR2_ATEN);
> +	ucr2 &= ~(UCR2_TXEN | UCR2_CTSC | UCR2_CTS | UCR2_ATEN);
>  	imx_uart_writel(sport, ucr2, UCR2);
>  	spin_unlock_irqrestore(&sport->port.lock, flags);

While this doesn't change behaviour (which is of course good and
intended here) I wonder if changing RTS is right here.

According to Documentation/serial/driver it is not.

Best regards
Uwe

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