[U-Boot-Users] [PATCH V2] Round the serial port clock divisor value returned by calc_divisor()

Hugo Villeneuve
2008-07-08T18:54:58Z

Round the serial port clock divisor value returned by
calc_divisor().

Signed-off-by: Hugo Villeneuve <hugo.villeneuve@lyrtech.com>
Signed-off-by: John Roberts <john.roberts@pwav.com>

---

Rounding is important, especially when using high baud rates
values like 115200bps. When using the non-rounded value, some
boards will work and some won't.

drivers/serial/serial.c | 6 +++++-
1 files changed, 5 insertions(+), 1 deletions(-)

diff --git a/drivers/serial/serial.c b/drivers/serial/serial.c
index 76425d8..1192f07 100644
--- a/drivers/serial/serial.c
+++ b/drivers/serial/serial.c
@@ -144,8 +144,12 @@ static int calc_divisor (NS16550_t port)
#else
#define MODE_X_DIV 16
#endif
- return (CFG_NS16550_CLK / MODE_X_DIV / gd->baudrate);

+ /* Compute divisor value. Normally, we should simply return:
+ * CFG_NS16550_CLK) / MODE_X_DIV / gd->baudrate
+ * 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;
}

#if !defined(CONFIG_SERIAL_MULTI)