Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758124AbYFQVdc (ORCPT ); Tue, 17 Jun 2008 17:33:32 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1756794AbYFQVdY (ORCPT ); Tue, 17 Jun 2008 17:33:24 -0400 Received: from wa-out-1112.google.com ([209.85.146.180]:5241 "EHLO wa-out-1112.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756086AbYFQVdX (ORCPT ); Tue, 17 Jun 2008 17:33:23 -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=l7yZTq/4jS/dDW+kyxDoMKB2lU3QTy2WgRPTHkPVu8ZSdqMVW4BbKxrrZMS4o3LZdw EIx0m6tH25JjcUV257mUrijngmzcfXBgIF5x4/NwRJMHXODC6nwx78HX88R2XKtSBx5U 9Isdf9XY3bgXTqZIK6tOK7lxp0mBDOOGc7bJs= Message-ID: Date: Wed, 18 Jun 2008 00:33:21 +0300 From: "Nameer Yarkon" To: "Alan Cox" Subject: Re: Serial problem and request for guidance.. Cc: linux-kernel@vger.kernel.org In-Reply-To: <20080616130353.1b80fdd0@lxorguk.ukuu.org.uk> MIME-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Content-Disposition: inline References: <20080616130353.1b80fdd0@lxorguk.ukuu.org.uk> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1705 Lines: 35 On Mon, Jun 16, 2008 at 3:03 PM, Alan Cox wrote: >> Some of my serial rx data gets lost. > > Which hardware ? It's a range of platforms/kernel versions and scenarios. Currently it happens with a bluetooth device connected to standard UART on ARM (OMAP) with an old 2.6.14 kernel, but only when I enable the debug macros of the line discipline code (hci_h4, hci_ldisc,..). When a big chunk of data arrives, more than half of it is lost. even on 115200. But when I turn of the debug macros (BT_DBG macros which are simply a bunch of prinks) the problem disappears. So I suspect there are some nasty timing issues which lead to data loss. I encountered similar problems last year even on a PC, with pre 2.6.21 kernels (around 2.6.19 or even earlier IIRC) but it was all gone with 2.6.21 and 2.6.22. Currently I have totally different machines, and these devices tend now to come with USB-to-serial connectors so I'm not quite sure about up-to-date kernels yet. All I can say is that it is nasty and very hard to debug, and I'm not quite sure how can I debug it as I find the serial/tty subsystems a bit perplexing. I know this is not necessarily relevant to the tip of the kernel, and it still lacks many details, but any guidance towards how can I debug it will be much appreciated. If I will successfully reproduce it with a current kernel I promise a full and detailed bug report. Thank you for your time and patience ! Nameer. -- 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/