linux-kernel - Re: [PATCH v3 10/15] serial: stm32-usart: Add STM32 USART Driver

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Message-ID: <CALszF6DX2pz_US6uqQwBjmZhfgjw5PP1UAy9H+c-_Kgkk_Z72w@mail.gmail.com>
Date:	Thu, 19 Mar 2015 18:35:30 +0100
From:	Maxime Coquelin <mcoquelin.stm32@...il.com>
To:	Peter Hurley <peter@...leysoftware.com>
Cc:	Andy Shevchenko <andy.shevchenko@...il.com>,
	Uwe Kleine-König 
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Subject: Re: [PATCH v3 10/15] serial: stm32-usart: Add STM32 USART Driver

2015-03-19 15:58 GMT+01:00 Peter Hurley <peter@...leysoftware.com>:
> 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.

Ok, I will refactor the implementation, and comment it.

Regards,
Maxime

>
> Regards,
> Peter Hurley
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