From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jerry Van Baren Date: Thu, 29 May 2008 13:37:26 -0400 Subject: [U-Boot-Users] [PATCH] ColdFire: Fix UART baudrate formula In-Reply-To: <1212082166-29933-1-git-send-email-Tsi-Chung.Liew@freescale.com> References: <1212082166-29933-1-git-send-email-Tsi-Chung.Liew@freescale.com> Message-ID: <483EE9D6.9080404@ge.com> List-Id: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: u-boot@lists.denx.de Tsi-Chung.Liew wrote: > From: TsiChung Liew > > 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 > Signed-off-by: TsiChung Liew > --- > 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);