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

[Hugo Villeneuve]

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

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