linux-kernel - Re: [PATCH RFC] serial: mxs-auart: fix baud rate range

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Date:	Mon, 10 Aug 2015 19:01:27 +0200
From:	Janusz Użycki <j.uzycki@...romaelectronics.com>
To:	Fabio Estevam <festevam@...il.com>,
	Stefan Wahren <stefan.wahren@...e.com>
Cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Jiri Slaby <jslaby@...e.com>,
	Janusz Uzycki <j.uzycki@...roma.com.pl>,
	Fabio Estevam <fabio.estevam@...escale.com>,
	Juergen Beisert <jbe@...gutronix.de>,
	"linux-serial@...r.kernel.org" <linux-serial@...r.kernel.org>,
	linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH RFC] serial: mxs-auart: fix baud rate range



W dniu 2015-08-10 o 14:22, Fabio Estevam pisze:
> On Mon, Aug 10, 2015 at 9:12 AM, Stefan Wahren <stefan.wahren@...e.com> wrote:
>
>>          /* set baud rate */
>> -       baud = uart_get_baud_rate(u, termios, old, 0, u->uartclk);
>> +       baud_min = u->uartclk * 32 / 0x3fffc0;
>> +       baud_max = u->uartclk * 32 / 0xec;
>> +       baud = uart_get_baud_rate(u, termios, old, baud_min, baud_max);
> Looks good. It would be nice to replace 0x3fffc0 and 0xec with defines though.

I agree with Fabio.

In addition let's look at the example for uartclk = 24MHz:
baud_max = 3,254,237.29 => will be rounded down to 3,254,237bauds and it 
is OK
baud_min = 183.1 => will be rounded to 183 bauds. To avoid div=0x400971 
it should be 184
so DIV_ROUND_UP() macro could be used.

best regards
Janusz

>
> Regards,
>
> Fabio Estevam

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