From mboxrd@z Thu Jan 1 00:00:00 1970 From: Lee Howard Subject: Re: serial flow control appears broken Date: Fri, 27 Jul 2007 10:36:03 -0700 Message-ID: <46AA2D03.70800@howardsilvan.com> References: <46A84B4A.6070902@shaw.ca> <46A8C6F1.4080309@howardsilvan.com> <20070726173121.70088a92@the-village.bc.nu> <46A98845.8010806@howardsilvan.com> <20070727124715.20130b14@the-village.bc.nu> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Return-path: Received: from gateway.howardsilvan.com ([64.146.212.27]:38103 "EHLO mail.howardsilvan.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756903AbXG0RhR (ORCPT ); Fri, 27 Jul 2007 13:37:17 -0400 In-Reply-To: <20070727124715.20130b14@the-village.bc.nu> Sender: linux-serial-owner@vger.kernel.org List-Id: linux-serial@vger.kernel.org To: Alan Cox Cc: Robert Hancock , linux-serial@vger.kernel.org Alan Cox wrote: >>So, does this explain why I wouldn't have a problem at 115200 bps with >>kernel 2.2.5 but why I do with 2.6.5 and 2.6.18? Both hardware and >> >> > >Without a scope on the board running both 2.2 and 2.6 that would be hard >to tell. > > I see. Unfortunately I don't have a scope here in my office. The modem manufacturer does have a scope, but they only have a system running 2.6. I suppose I could have them return the test system that I sent to them and I could reinstall it with 2.2... if you feel like that will help. >You are >making assumptions that seem unwise - eg that the code didn't happen to >work in 2.2.5 even though it was not correctly setting hardware flow >control, or that the defaults set by the user space apps run with the >distribution haven't changed and thus shown up such a problem. > > Understood. Please let me know the systematic approach that you would like me to follow in debugging this. >Also was the 2.2 and 2.6 on the same exact mainboard ? > > Yes. I have several hard drives with various installations on them. I just plug whichever drive in that I want to use for the OS version installed. So I've got a drive with RedHat 6.0 (kernel 2.2.5) and a separate drive with Fedora Core 2 (2.6.5). The installation that I did for the manufacturer on a separate machine is Fedora Core 6 (2.6.18). >You've verified that flow control does not seem to be getting asserted >for h/w control on the wires > > The manufacturer has verified this with their scope. I can ony do this by watching the RTS LED on the modem... which may or may not be a reliable way to monitor things. >Next question on the software side therefore is does the serial port have >CRTSCTS set when the problem is showing up. (stty -a Yes. Here's what it looks like: # stty -F /dev/ttyS1 -a speed 115200 baud; rows 0; columns 0; line = 0; intr = ^C; quit = ^\; erase = ^?; kill = ^U; eof = ^D; eol = ; eol2 = ; start = ^Q; stop = ^S; susp = ^Z; rprnt = ^R; werase = ^W; lnext = ^V; flush = ^O; min = 1; time = 0; -parenb -parodd cs8 -hupcl -cstopb cread clocal crtscts -ignbrk -brkint -ignpar -parmrk -inpck -istrip -inlcr -igncr -icrnl -ixon -ixoff -iuclc -ixany -imaxbel -opost -olcuc -ocrnl -onlcr -onocr -onlret -ofill -ofdel nl0 cr0 tab0 bs0 vt0 ff0 -isig -icanon -iexten -echo -echoe -echok -echonl -noflsh -xcase -tostop -echoprt -echoctl -echoke # Thanks, Lee.