From mboxrd@z Thu Jan 1 00:00:00 1970 From: Dick Hollenbeck Subject: [PATCH] serial8250_tx_empty not telling the truth Date: Sat, 26 Sep 2009 15:21:43 -0500 Message-ID: <4ABE77D7.3090609@softplc.com> Mime-Version: 1.0 Content-Type: multipart/mixed; boundary="------------010105040408060806060101" Return-path: Received: from kcmailp01.birch.net ([216.212.0.96]:51060 "EHLO mx01.birch.net" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1750795AbZIZUVk (ORCPT ); Sat, 26 Sep 2009 16:21:40 -0400 Received: from unknown (HELO [192.100.100.10]) ([65.16.135.194]) (envelope-sender ) by mx01.birch.net (qmail-ldap-1.03) with SMTP for ; 26 Sep 2009 20:21:43 -0000 Sender: linux-serial-owner@vger.kernel.org List-Id: linux-serial@vger.kernel.org To: linux-serial@vger.kernel.org This is a multi-part message in MIME format. --------------010105040408060806060101 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit When controlling an industrial radio modem it can be necessary to manipulate the handshake lines in order to control the radio modem's transmitter. The transmitter should not be turned off before all characters have been transmitted. serial8250_tx_empty() was reporting that all characters were transmitted before they actually were. Signed-off-by: Dick Hollenbeck --------------010105040408060806060101 Content-Type: text/x-diff; name="8250.diff" Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="8250.diff" --- drivers/serial/8250.c.orig 2009-09-26 14:06:55.000000000 -0500 +++ drivers/serial/8250.c 2009-09-26 14:12:37.000000000 -0500 @@ -81,6 +81,9 @@ static int serial_index(struct uart_port #define PASS_LIMIT 256 +#define BOTH_EMPTY (UART_LSR_TEMT | UART_LSR_THRE) + + /* * We default to IRQ0 for the "no irq" hack. Some * machine types want others as well - they're free @@ -1792,7 +1795,7 @@ static unsigned int serial8250_tx_empty( up->lsr_saved_flags |= lsr & LSR_SAVE_FLAGS; spin_unlock_irqrestore(&up->port.lock, flags); - return lsr & UART_LSR_TEMT ? TIOCSER_TEMT : 0; + return (lsr & BOTH_EMPTY) == BOTH_EMPTY ? TIOCSER_TEMT : 0; } static unsigned int serial8250_get_mctrl(struct uart_port *port) @@ -1850,8 +1853,6 @@ static void serial8250_break_ctl(struct spin_unlock_irqrestore(&up->port.lock, flags); } -#define BOTH_EMPTY (UART_LSR_TEMT | UART_LSR_THRE) - /* * Wait for transmitter & holding register to empty */ --------------010105040408060806060101--