[U-Boot-Users] [PATCH] Round the serial port clock divisor value returned by calc_divisor()

Jerry Van Baren
2008-07-11T01:25:40Z

This formula is better at avoiding integer overflow.

Signed-off-by: Gerald Van Baren <vanbaren@cideas.com>
---

(try 2)

The formula I proposed previously in this thread compiles OK. I cannot
verify it is correct on real hardware, however.
<http://thread.gmane.org/gmane.comp.boot-loaders.u-boot/43499/focus=43506>

Best regards,
gvb

drivers/serial/serial.c | 4 +++-
1 files changed, 3 insertions(+), 1 deletions(-)

diff --git a/drivers/serial/serial.c b/drivers/serial/serial.c
index 182ca2d..48579ae 100644
--- a/drivers/serial/serial.c
+++ b/drivers/serial/serial.c
@@ -150,7 +150,9 @@ static int calc_divisor (NS16550_t port)
* but we need to round that value by adding 0.5 or 8/16.
* Rounding is especially important at high baud rates.
*/
- return (((16 * CFG_NS16550_CLK) / MODE_X_DIV / gd->baudrate) + 8) / 16;
+ return (CFG_NS16550_CLK + (gd->baudrate / 2)) /
+ (MODE_X_DIV * gd->baudrate);
+
}

#if !defined(CONFIG_SERIAL_MULTI)
--
1.5.6