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

On 03/19/2015 09:55 AM, Maxime Coquelin wrote:

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+static void stm32_set_termios(struct uart_port *port, struct ktermios *termios,
+                           struct ktermios *old)

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+       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);
+       }

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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