linux-kernel - Re: [PATCH] tty: serial: fsl_lpuart: minimum baud rate support

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Message-ID: <20200625100410.GA3327034@kroah.com>
Date:   Thu, 25 Jun 2020 12:04:10 +0200
From:   Greg KH <gregkh@...uxfoundation.org>
To:     Vabhav Sharma <vabhav.sharma@....nxp.com>
Cc:     jslaby@...e.com, linux-serial@...r.kernel.org,
        linux-kernel@...r.kernel.org, v.sethi@....com,
        Vabhav Sharma <vabhav.sharma@....com>
Subject: Re: [PATCH] tty: serial: fsl_lpuart: minimum baud rate support

On Thu, Jun 25, 2020 at 03:19:05PM +0530, Vabhav Sharma wrote:
> From: Vabhav Sharma <vabhav.sharma@....com>
> 
> The formula for the baud rate is
> baud rate = "baud clock / ((OSR+1) × SBR)
> 
> Algorithm used in function lpuart32_serial_setbrg() only changes
> the SBR. Even with maxmum value put in, OSR stays at 0x7 and the
> lowest baud rate would be ~ 2600 bps
> 
> Update the algorithm to allow driver operation at 1200,2400 or
> 600 bps
> 
> Signed-off-by: Vabhav Sharma <vabhav.sharma@....com>
> ---
>  drivers/tty/serial/fsl_lpuart.c | 4 ++++
>  1 file changed, 4 insertions(+)
> 
> diff --git a/drivers/tty/serial/fsl_lpuart.c b/drivers/tty/serial/fsl_lpuart.c
> index 90298c4..0fd0fa5f 100644
> --- a/drivers/tty/serial/fsl_lpuart.c
> +++ b/drivers/tty/serial/fsl_lpuart.c
> @@ -1925,6 +1925,10 @@ static void __lpuart32_serial_setbrg(struct uart_port *port,
>  			tmp_sbr++;
>  		}
>  
> +		if (tmp_sbr > UARTBAUD_SBR_MASK) {
> +			continue;
> +		}

Always use scripts/checkpatch.pl on your patches so you do not get
grumpy emails from maintainers telling you to use scripts/checkpatch.pl
on your patches...