linux-kernel - Re: [PATCH] serial: samsung: Reorder the sequence of clock control when call s3c24xx_serial_set

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Date:	Fri, 25 Mar 2016 09:10:16 +0900
From:	Chanwoo Choi <cw00.choi@...sung.com>
To:	gregkh@...uxfoundation.org, jslaby@...e.com
Cc:	k.kozlowski@...sung.com, kgene@...nel.org,
	linux-serial@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-samsung-soc@...r.kernel.org,
	"Robert Baldyga (SRPOL)" <r.baldyga@...sung.com>
Subject: Re: [PATCH] serial: samsung: Reorder the sequence of clock control
 when call s3c24xx_serial_set_termios()

Hi Robert,

I send following patch to fix the broken serial log of Exynos SoC.
As I knew, you also knew this issue.
If possible, could you review or test this patch?

Best Regards,
Chanwoo Choi

On 2016년 03월 14일 09:41, Chanwoo Choi wrote:
> This patch fixes the broken serial log when changing the clock source
> of uart device. Before disabling the original clock source, this patch
> enables the new clock source to protect the clock off state for a split second.
> 
> Signed-off-by: Chanwoo Choi <cw00.choi@...sung.com>
> ---
>  drivers/tty/serial/samsung.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/tty/serial/samsung.c b/drivers/tty/serial/samsung.c
> index d72cd736bdc6..80d59dbfebba 100644
> --- a/drivers/tty/serial/samsung.c
> +++ b/drivers/tty/serial/samsung.c
> @@ -1265,13 +1265,13 @@ static void s3c24xx_serial_set_termios(struct uart_port *port,
>  	if (ourport->baudclk != clk) {
>  		s3c24xx_serial_setsource(port, clk_sel);
>  
> +		clk_prepare_enable(clk);
> +
>  		if (!IS_ERR(ourport->baudclk)) {
>  			clk_disable_unprepare(ourport->baudclk);
>  			ourport->baudclk = ERR_PTR(-EINVAL);
>  		}
>  
> -		clk_prepare_enable(clk);
> -
>  		ourport->baudclk = clk;
>  		ourport->baudclk_rate = clk ? clk_get_rate(clk) : 0;
>  	}
>