From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751888AbWI1Nbe (ORCPT ); Thu, 28 Sep 2006 09:31:34 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751891AbWI1Nbe (ORCPT ); Thu, 28 Sep 2006 09:31:34 -0400 Received: from nat-132.atmel.no ([80.232.32.132]:48863 "EHLO relay.atmel.no") by vger.kernel.org with ESMTP id S1751888AbWI1Nbd (ORCPT ); Thu, 28 Sep 2006 09:31:33 -0400 From: Haavard Skinnemoen To: Andrew Victor Cc: Russell King , linux-kernel@vger.kernel.org, Haavard Skinnemoen Subject: [PATCH 4/4] atmel_serial: Fix roundoff error in atmel_console_get_options Reply-To: Haavard Skinnemoen Date: Thu, 28 Sep 2006 15:31:42 +0200 Message-Id: <11594503023165-git-send-email-hskinnemoen@atmel.com> X-Mailer: git-send-email 1.4.1.1 In-Reply-To: <1159450302567-git-send-email-hskinnemoen@atmel.com> References: <11594503023218-git-send-email-hskinnemoen@atmel.com> <11594503023213-git-send-email-hskinnemoen@atmel.com> <11594503023619-git-send-email-hskinnemoen@atmel.com> <1159450302567-git-send-email-hskinnemoen@atmel.com> Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org The atmel_console_get_options() function initializes the baud, parity and bits settings from the actual hardware setup, in case it has been initialized by a e.g. boot loader. The baud rate, however, is not necessarily exactly equal to one of the standard baud rates (115200, etc.) This means that the baud rate calculated by this function may be slightly higher or slightly lower than one of the standard baud rates. If the baud rate is slightly lower than the target, this causes problems when uart_set_option() tries to match the detected baud rate against the standard baud rate, as it will always select a baud rate that is lower or equal to the target rate. For example if the detected baud rate is slightly lower than 115200, usart_set_options() will select 57600. This patch fixes the problem by subtracting 1 from the value in BRGR when calculating the baud rate. The detected baud rate will thus always be higher than the nearest standard baud rate, and uart_set_options() will end up doing the right thing. Tested on ATSTK1000 and AT91RM9200-EK boards. Both are broken without this patch. Signed-off-by: Haavard Skinnemoen --- drivers/serial/atmel_serial.c | 8 +++++++- 1 files changed, 7 insertions(+), 1 deletions(-) diff --git a/drivers/serial/atmel_serial.c b/drivers/serial/atmel_serial.c index 6f1f4ea..2613a7e 100644 --- a/drivers/serial/atmel_serial.c +++ b/drivers/serial/atmel_serial.c @@ -793,8 +793,14 @@ static void __init atmel_console_get_opt else if (mr == ATMEL_US_PAR_ODD) *parity = 'o'; + /* + * The serial core only rounds down when matching this to a + * supported baud rate. Make sure we don't end up slightly + * lower than one of those, as it would make us fall through + * to a much lower baud rate than we really want. + */ quot = UART_GET_BRGR(port); - *baud = port->uartclk / (16 * (quot)); + *baud = port->uartclk / (16 * (quot - 1)); } static int __init atmel_console_setup(struct console *co, char *options) -- 1.4.1.1