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Commit e97e1556 authored by Alexander Shiyan's avatar Alexander Shiyan Committed by Greg Kroah-Hartman
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serial: max310x: Setup baud rate generator more precisely 



This patch provide more precisely setup of baud rate generator.
If the result of division has a remainder, we use the multiplier
for the base frequency. Additionally, we report result baud rate
back to serial core.

Signed-off-by: default avatarAlexander Shiyan <shc_work@mail.ru>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent d0fd413c

drivers/tty/serial/max310x.c

+20 −12
Original line number Diff line number Diff line 
/*

 *  Maxim (Dallas) MAX3107/8/9, MAX14830 serial driver

 *

 *  Copyright (C) 2012-2013 Alexander Shiyan <shc_work@mail.ru>

 *  Copyright (C) 2012-2014 Alexander Shiyan <shc_work@mail.ru>

 *

 *  Based on max3100.c, by Christian Pellegrin <chripell@evolware.org>

 *  Based on max3110.c, by Feng Tang <feng.tang@intel.com>
@@ -504,25 +504,33 @@ static bool max310x_reg_precious(struct device *dev, unsigned int reg) 
	return false;

}



static void max310x_set_baud(struct uart_port *port, int baud)

static int max310x_set_baud(struct uart_port *port, int baud)

{

	unsigned int mode = 0, div = port->uartclk / baud;

	unsigned int mode = 0, clk = port->uartclk, div = clk / baud;



	if (!(div / 16)) {

	/* Check for minimal value for divider */

	if (div < 16)

		div = 16;



	if (clk % baud && (div / 16) < 0x8000) {

		/* Mode x2 */

		mode = MAX310X_BRGCFG_2XMODE_BIT;

		div = (port->uartclk * 2) / baud;

	}

		clk = port->uartclk * 2;

		div = clk / baud;



	if (!(div / 16)) {

		if (clk % baud && (div / 16) < 0x8000) {

			/* Mode x4 */

			mode = MAX310X_BRGCFG_4XMODE_BIT;

		div = (port->uartclk * 4) / baud;

			clk = port->uartclk * 4;

			div = clk / baud;

		}

	}



	max310x_port_write(port, MAX310X_BRGDIVMSB_REG, (div / 16) >> 8);

	max310x_port_write(port, MAX310X_BRGDIVLSB_REG, div / 16);

	max310x_port_write(port, MAX310X_BRGCFG_REG, (div % 16) | mode);



	return DIV_ROUND_CLOSEST(clk, div);

}



static int max310x_update_best_err(unsigned long f, long *besterr)
@@ -875,7 +883,7 @@ static void max310x_set_termios(struct uart_port *port, 
				  port->uartclk / 4);



	/* Setup baudrate generator */

	max310x_set_baud(port, baud);

	baud = max310x_set_baud(port, baud);



	/* Update timeout according to new baud rate */

	uart_update_timeout(port, termios->c_cflag, baud);