linux-kernel - Re: [PATCH 3/4] tty: serial: samsung: Increase maximum baudrate

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Message-ID: <20181221101553.GI13248@dell>
Date:   Fri, 21 Dec 2018 10:15:53 +0000
From:   Lee Jones <lee.jones@...aro.org>
To:     Marek Szyprowski <m.szyprowski@...sung.com>
Cc:     linux-kernel@...r.kernel.org, linux-serial@...r.kernel.org,
        linux-samsung-soc@...r.kernel.org,
        Krzysztof Kozlowski <krzk@...nel.org>,
        Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>,
        Beomho Seo <beomho.seo@...sung.com>,
        Seung-Woo Kim <sw0312.kim@...sung.com>,
        Sylwester Nawrocki <s.nawrocki@...sung.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Subject: Re: [PATCH 3/4] tty: serial: samsung: Increase maximum baudrate

On Fri, 14 Dec 2018, Marek Szyprowski wrote:

> From: Seung-Woo Kim <sw0312.kim@...sung.com>
> 
> This driver can be used to communicate with Bluetooth chip in high-speed
> UART mode, so increase the maximum baudrate to 3Mbps.
> 
> Signed-off-by: Seung-Woo Kim <sw0312.kim@...sung.com>
> [mszyprow: rephrased commit message]
> Signed-off-by: Marek Szyprowski <m.szyprowski@...sung.com>
> ---
>  drivers/tty/serial/samsung.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/tty/serial/samsung.c b/drivers/tty/serial/samsung.c
> index 2a49b6d876b8..9fc3559f80d9 100644
> --- a/drivers/tty/serial/samsung.c
> +++ b/drivers/tty/serial/samsung.c
> @@ -1287,7 +1287,7 @@ static void s3c24xx_serial_set_termios(struct uart_port *port,
>  	 * Ask the core to calculate the divisor for us.
>  	 */
>  
> -	baud = uart_get_baud_rate(port, termios, old, 0, 115200*8);
> +	baud = uart_get_baud_rate(port, termios, old, 0, 3000000);

Does that mean the low speed devices will stop working?  It looks like
this should be dynamically configurable based on what device is
connected to it, no?

>  	quot = s3c24xx_serial_getclk(ourport, baud, &clk, &clk_sel);
>  	if (baud == 38400 && (port->flags & UPF_SPD_MASK) == UPF_SPD_CUST)
>  		quot = port->custom_divisor;

-- 
Lee Jones [李琼斯]
Linaro Services Technical Lead
Linaro.org │ Open source software for ARM SoCs
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