[U-Boot-Users] [PATCH] ColdFire: Fix UART baudrate formula

[Jerry Van Baren <gerald.vanbaren@ge.com>]

Tsi-Chung.Liew wrote:
> From: TsiChung Liew <Tsi-Chung.Liew@freescale.com>
> 
> Replace counter = bus_clk / (baudrate * 32) with
> counter = ((bus_clk / 32) + (baudrate /2 )) / baudrate
> formula

I assume it works. :-)

Your comment is a duplicate of the code.  A better comment would tell 
the reader *why* you made the change.  Suggestion...

The formula "counter = (u32) (gd->bus_clk / (gd->baudrate)) / 32" can 
generate the wrong divisor due to integer division truncation.  Round 
the calculated divisor value by adding 1/2 the baudrate before dividing 
by the baudrate.

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

> Signed-off-by: TsiChung Liew <Tsi-Chung.Liew@freescale.com>
> ---
>  drivers/serial/mcfuart.c |    4 ++--
>  1 files changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/serial/mcfuart.c b/drivers/serial/mcfuart.c
> index 88f3eb1..75e85b7 100644
> --- a/drivers/serial/mcfuart.c
> +++ b/drivers/serial/mcfuart.c
> @@ -63,8 +63,8 @@ int serial_init(void)
>  	uart->umr = UART_UMR_SB_STOP_BITS_1;
>  
>  	/* Setting up BaudRate */
> -	counter = (u32) (gd->bus_clk / (gd->baudrate));
> -	counter >>= 5;
> +	counter = (u32) (gd->bus_clk / 32) + (gd->baudrate / 2));
> +	counter = counter / gd->baudrate;
>  
>  	/* write to CTUR: divide counter upper byte */
>  	uart->ubg1 = (u8) ((counter & 0xff00) >> 8);