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Fix integer overflow warning in calc_divisor()

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which happened when rounding the serial port clock divisor

Signed-off-by: Hugo Villeneuve <hugo.villeneuve@lyrtech.com>
This commit is contained in:
Hugo Villeneuve 2008-07-11 10:24:15 -04:00 committed by Wolfgang Denk
parent 6b760189d7
commit ef130d3093
1 changed files with 9 additions and 2 deletions
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11
drivers/serial/serial.c
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@ -124,6 +124,8 @@ static NS16550_t serial_ports[4] = {
static int calc_divisor (NS16550_t port) static int calc_divisor (NS16550_t port)
{ {
uint32_t clk_divisor;
#ifdef CONFIG_OMAP1510 #ifdef CONFIG_OMAP1510
/* If can't cleanly clock 115200 set div to 1 */ /* If can't cleanly clock 115200 set div to 1 */
if ((CFG_NS16550_CLK == 12000000) && (gd->baudrate == 115200)) { if ((CFG_NS16550_CLK == 12000000) && (gd->baudrate == 115200)) {
@ -147,10 +149,15 @@ static int calc_divisor (NS16550_t port)
/* Compute divisor value. Normally, we should simply return: /* Compute divisor value. Normally, we should simply return:
* CFG_NS16550_CLK) / MODE_X_DIV / gd->baudrate * CFG_NS16550_CLK) / MODE_X_DIV / gd->baudrate
* but we need to round that value by adding 0.5 or 8/16. * but we need to round that value by adding 0.5 (2/4).
* Rounding is especially important at high baud rates. * Rounding is especially important at high baud rates.
*/ */
return (((16 * CFG_NS16550_CLK) / MODE_X_DIV / gd->baudrate) + 8) / 16; clk_divisor = (((4 * CFG_NS16550_CLK) /
(MODE_X_DIV * gd->baudrate)) + 2) / 4;
debug("NS16550 clock divisor = %d\n", clk_divisor);
return clk_divisor;
} }
#if !defined(CONFIG_SERIAL_MULTI) #if !defined(CONFIG_SERIAL_MULTI)