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Date: Thu, 19 Mar 2015 10:58:36 -0400
From: Peter Hurley <peter@hurleysoftware.com>
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To: Maxime Coquelin <mcoquelin.stm32@gmail.com>,
        Andy Shevchenko <andy.shevchenko@gmail.com>
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Subject: Re: [PATCH v3 10/15] serial: stm32-usart: Add STM32 USART Driver
References: <1426197361-19290-1-git-send-email-maxime.coquelin@st.com>	<1426197361-19290-11-git-send-email-maxime.coquelin@st.com>	<CAHp75Vd7+oLiLLuyocYh95TebtocWrRho6xNjuSUt8fYGp8npg@mail.gmail.com>	<CALszF6BWuUYRh+3rWnSQLApkAHA5dQXw=6x6D_evRtb+5B_ukA@mail.gmail.com>	<CAHp75Vdf6=z1d5+eYJ+QGTko9kkZf-oPfoWaf8FRoTdqcdWxjw@mail.gmail.com> <CALszF6A5Zu7i0hxSLTS-nfOAXmd0__jLjB=fHxK93Ex5Vbi9LA@mail.gmail.com>
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On 03/19/2015 09:55 AM, Maxime Coquelin wrote:
>>>>> +static void stm32_set_termios(struct uart_port *port, struct ktermios *termios,
>>>>> +                           struct ktermios *old)
[...]
>>>>> +       usardiv = (port->uartclk * 25) / (baud * 4);
>>>>> +       mantissa = (usardiv / 100) << USART_BRR_DIV_M_SHIFT;
>>>>> +       fraction = DIV_ROUND_CLOSEST((usardiv % 100) * 16, 100);
>>>>> +       if (fraction & ~USART_BRR_DIV_F_MASK) {
>>>>> +               fraction = 0;
>>>>> +               mantissa += (1 << USART_BRR_DIV_M_SHIFT);
>>>>> +       }
[...]
> Really, I would prefer keeping this fractional divider as it is
> implemented today.

You have to admit that's basically an unintelligible mess;
how would anyone ever be able to refactor and replace that with a
common divider implementation?

At the very least, please comment on the formula and format.

Regards,
Peter Hurley