ColdFire: Fix UART baudrate formula
PATCH 1/1 ColdFire: Fix UART baudrate formula
From: TsiChung Liew <[email protected]>
Replace counter = bus_clk / (baudrate * 32) with counter = ((bus_clk / 32) + (baudrate /2 )) / baudrate formula
--- drivers/serial/mcfuart.c | 4 ++-- 1 files changed, 2 insertions(+), 2 deletions(-)
drivers/serial/mcfuart.c +2 -2
@@ -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 );
Signature · 1 line
1.5.4.1
PATCH 1/1 ColdFire: Fix UART baudrate formula
Quoted 5 lines · Tsi-Chung.Liew
From: TsiChung Liew <[email protected]>
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.
Quoted 20 lines
Signed-off-by TsiChung Liew <[email protected]>--- drivers/serial/mcfuart.c | 4 ++-- 1 files changed, 2 insertions(+), 2 deletions(-)drivers/serial/mcfuart.c +2
-2@@ -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 );