Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752335Ab2HGI0S (ORCPT ); Tue, 7 Aug 2012 04:26:18 -0400 Received: from co1ehsobe006.messaging.microsoft.com ([216.32.180.189]:26552 "EHLO co1outboundpool.messaging.microsoft.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750815Ab2HGI0P (ORCPT ); Tue, 7 Aug 2012 04:26:15 -0400 X-Forefront-Antispam-Report: CIP:70.37.183.190;KIP:(null);UIP:(null);IPV:NLI;H:mail.freescale.net;RD:none;EFVD:NLI X-SpamScore: 3 X-BigFish: VS3(zzzz1202h1082kzz8275bhz2dh2a8h668h839hd24he5bhf0ah107ah) From: Huang Shijie To: CC: , , , , Huang Shijie Subject: [PATCH] serial: mxs-auart: fix the wrong RTS hardware flow control Date: Tue, 7 Aug 2012 16:10:52 +0800 Message-ID: <1344327052-8127-1-git-send-email-b32955@freescale.com> X-Mailer: git-send-email 1.7.0.4 MIME-Version: 1.0 Content-Type: text/plain X-OriginatorOrg: freescale.com Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2451 Lines: 70 Without checking if the auart supports the hardware flow control or not, the old mxs_auart_set_mctrl() asserted the RTS pin blindly. This will causes the auart receives wrong data in the following case: The far-end has already started the write operation, and wait for the auart asserts the RTS pin. Then the auart starts the read operation, but mxs_auart_set_mctrl() may be called before we set the RTSCTS in the mxs_auart_settermios(). So the RTS pin is asserted in a wrong situation, and we get the wrong data in the end. This bug has been catched when I connect the mx23(DTE) to the mx53(DCE). This patch also replaces the AUART_CTRL2_RTS with AUART_CTRL2_RTSEN. We should use the real the hardware flow control, not the software-controled hardware flow control. Signed-off-by: Huang Shijie --- drivers/tty/serial/mxs-auart.c | 14 +++++++++----- 1 files changed, 9 insertions(+), 5 deletions(-) diff --git a/drivers/tty/serial/mxs-auart.c b/drivers/tty/serial/mxs-auart.c index 2e341b8..97f32e3 100644 --- a/drivers/tty/serial/mxs-auart.c +++ b/drivers/tty/serial/mxs-auart.c @@ -73,6 +73,7 @@ #define AUART_CTRL0_CLKGATE (1 << 30) #define AUART_CTRL2_CTSEN (1 << 15) +#define AUART_CTRL2_RTSEN (1 << 14) #define AUART_CTRL2_RTS (1 << 11) #define AUART_CTRL2_RXE (1 << 9) #define AUART_CTRL2_TXE (1 << 8) @@ -259,9 +260,12 @@ static void mxs_auart_set_mctrl(struct uart_port *u, unsigned mctrl) u32 ctrl = readl(u->membase + AUART_CTRL2); - ctrl &= ~AUART_CTRL2_RTS; - if (mctrl & TIOCM_RTS) - ctrl |= AUART_CTRL2_RTS; + ctrl &= ~AUART_CTRL2_RTSEN; + if (mctrl & TIOCM_RTS) { + if (u->flags & ASYNC_CTS_FLOW) + ctrl |= AUART_CTRL2_RTSEN; + } + s->ctrl = mctrl; writel(ctrl, u->membase + AUART_CTRL2); } @@ -359,9 +363,9 @@ static void mxs_auart_settermios(struct uart_port *u, /* figure out the hardware flow control settings */ if (cflag & CRTSCTS) - ctrl2 |= AUART_CTRL2_CTSEN; + ctrl2 |= AUART_CTRL2_CTSEN | AUART_CTRL2_RTSEN; else - ctrl2 &= ~AUART_CTRL2_CTSEN; + ctrl2 &= ~(AUART_CTRL2_CTSEN | AUART_CTRL2_RTSEN); /* set baud rate */ baud = uart_get_baud_rate(u, termios, old, 0, u->uartclk); -- 1.7.0.4 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/