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Subject[PATCH 7/8] imx: serial: use rational library function
Date
for calculation of numerator and denominator
used in baud rate setting, use generic library function
for optimum settings.

Signed-off-by: Oskar Schirmer <os@emlix.com>
---
drivers/serial/Kconfig | 1 +
drivers/serial/imx.c | 30 ++++++++++--------------------
2 files changed, 11 insertions(+), 20 deletions(-)

diff --git a/drivers/serial/Kconfig b/drivers/serial/Kconfig
index 343e3a3..0ecb4c4 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 60892a2..11f93e2 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
--
1.5.3.7


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