2 files changed, 11 insertions, 20 deletions

diff --git a/drivers/serial/Kconfig b/drivers/serial/Kconfig
index 3391ef0d761..641e800ed69 100644
--- a/drivers/serial/Kconfig
+++ b/drivers/serial/Kconfig
@@ -833,6 +833,7 @@ config SERIAL_IMX
         bool "IMX serial port support"
         depends on ARM && (ARCH_IMX || ARCH_MXC)
         select SERIAL_CORE
+        select RATIONAL
         help
           If you have a machine based on a Motorola IMX CPU you
           can enable its onboard serial port by enabling this option.
diff --git a/drivers/serial/imx.c b/drivers/serial/imx.c
index cbd4f322464..0de81f71f88 100644
--- a/drivers/serial/imx.c
+++ b/drivers/serial/imx.c
@@ -41,6 +41,7 @@
 #include <linux/serial_core.h>
 #include <linux/serial.h>
 #include <linux/clk.h>
+#include <linux/rational.h>
 
 #include <asm/io.h>
 #include <asm/irq.h>
@@ -670,7 +671,8 @@ imx_set_termios(struct uart_port *port, struct ktermios *termios,
         unsigned long flags;
         unsigned int ucr2, old_ucr1, old_txrxen, baud, quot;
         unsigned int old_csize = old ? old->c_cflag & CSIZE : CS8;
-        unsigned int div, num, denom, ufcr;
+        unsigned int div, ufcr;
+        unsigned long num, denom;
 
         /*
          * If we don't support modem control lines, don't allow
@@ -772,32 +774,20 @@ imx_set_termios(struct uart_port *port, struct ktermios *termios,
         if (!div)
                 div = 1;
 
-        num = baud;
-        denom = port->uartclk / div / 16;
+        rational_best_approximation(16 * div * baud, sport->port.uartclk,
+                1 << 16, 1 << 16, &num, &denom);
 
-        /* shift num and denom right until they fit into 16 bits */
-        while (num > 0x10000 || denom > 0x10000) {
-                num >>= 1;
-                denom >>= 1;
-        }
-        if (num > 0)
-                num -= 1;
-        if (denom > 0)
-                denom -= 1;
-
-        writel(num, sport->port.membase + UBIR);
-        writel(denom, sport->port.membase + UBMR);
-
-        if (div == 7)
-                div = 6; /* 6 in RFDIV means divide by 7 */
-        else
-                div = 6 - div;
+        num -= 1;
+        denom -= 1;
 
         ufcr = readl(sport->port.membase + UFCR);
         ufcr = (ufcr & (~UFCR_RFDIV)) |
             (div << 7);
         writel(ufcr, sport->port.membase + UFCR);
 
+        writel(num, sport->port.membase + UBIR);
+        writel(denom, sport->port.membase + UBMR);
+
 #ifdef ONEMS
         writel(sport->port.uartclk / div / 1000, sport->port.membase + ONEMS);
 #endif