Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756732AbYHABoF (ORCPT ); Thu, 31 Jul 2008 21:44:05 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753395AbYHABnx (ORCPT ); Thu, 31 Jul 2008 21:43:53 -0400 Received: from an-out-0708.google.com ([209.85.132.245]:23148 "EHLO an-out-0708.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751830AbYHABnw (ORCPT ); Thu, 31 Jul 2008 21:43:52 -0400 DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=message-id:date:from:to:subject:cc:in-reply-to:mime-version :content-type:content-transfer-encoding:content-disposition :references; b=tzp7tf5D+NOv0drHoV21x+sEGlcYSIxlEVsuEe4moHeS+t0hsYp1eTXp6Ec5CrLtAs LfEpJteVDGDKlURO/80fssFIuVz7hk50qhjX6nfRFzkNxMD/KWPYALkMSeHzivwZJzd9 lX5NpV6SPdy5agKrKOxsf+aaMwCV+ii3OQiaA= Message-ID: <7d1d9c250807311843j58246eeco4411ad9e5deda78a@mail.gmail.com> Date: Thu, 31 Jul 2008 21:43:50 -0400 From: "Paul Gortmaker" To: "Kumar Gala" Subject: Re: [RFC] suggested fix for 83xx/85xx PowerPC UART break bug Cc: "Paul Gortmaker" , linux-serial@vger.kernel.org, linux-kernel@vger.kernel.org In-Reply-To: MIME-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Content-Disposition: inline References: <20080731152616.GA14248@windriver.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2352 Lines: 53 On Thu, Jul 31, 2008 at 4:31 PM, Kumar Gala wrote: > > On Jul 31, 2008, at 10:26 AM, Paul Gortmaker wrote: > >> >> This is something I'd tripped over earlier, and wanted to follow up on >> to get an acceptable fix in for everyone's benefit before it falls through >> the cracks again. >> >> There seems to be an issue with recent 83xx/85xx SOC UARTs, in which a >> break >> triggers a short lived IRQ storm (hence killing any hope of using SysRQ). >> The only fix I found to work was to just ignore the bogus events that >> had the associated signature bit set. >> >> This fix is what I was using against earlier kernels, but I hate to add >> more >> board/arch specific ifdefs to files like 8250.c, so I'm wondering if >> anyone has any other suggestions before I simply end up cleaning up the >> boardlist (now ppc is dead) and respinning the patch much as it is now >> and resending. > > How did you test this or generate it? I was thinking about this the other > day and figured we need to try and track this down with the HW guys. If we > can generate a simple test I can try and run it through the various > boards/parts we have and see which ones show the issue and which dont. Actually, it is dead easy to reproduce. The obvious symptom is that you'll get a random complaint that SysRQ doesn't work. You send the break via whatever comm program you use, and 9 out of 10 times, you get the SysRQ help menu pop up immediately, before you've even entered another character. Once you dig a bit deeper, then you see that simply sending the break via the comm program (and nothing else) will result in roughly 300 to 2000 events as reported via "cat /proc/interrupts" on the UART in question. I've tested with at least 5 different boards, with minicom, ckermit and even with a commercial digiport in the path, and in all cases it came up the same. Paul. > > - k > -- > To unsubscribe from this list: send the line "unsubscribe linux-serial" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html > -- 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/