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: Alexander Shiyan <shc_work@mail.ru>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
diff --git a/drivers/tty/serial/max310x.c b/drivers/tty/serial/max310x.c
index 8d71e40..313bdf0 100644
--- a/drivers/tty/serial/max310x.c
+++ b/drivers/tty/serial/max310x.c
@@ -1,7 +1,7 @@
/*
* 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 @@
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)) {
- /* Mode x4 */
- mode = MAX310X_BRGCFG_4XMODE_BIT;
- div = (port->uartclk * 4) / baud;
+ if (clk % baud && (div / 16) < 0x8000) {
+ /* Mode x4 */
+ mode = MAX310X_BRGCFG_4XMODE_BIT;
+ 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 @@
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);