From mboxrd@z Thu Jan 1 00:00:00 1970 From: Russell King - ARM Linux Subject: Re: [PATCH] serial imx.c: fix CTS trigger level lower to avoid lost chars Date: Fri, 22 Jan 2010 16:57:19 +0000 Message-ID: <20100122165719.GB18461@n2100.arm.linux.org.uk> References: <1264109163-28739-1-git-send-email-valentin.longchamp@epfl.ch> <20100121220653.GA21010@pengutronix.de> <20100121221133.GA30419@n2100.arm.linux.org.uk> <4B597A82.4020906@epfl.ch> <20100122110701.GA15699@shareable.org> <20100122113130.GB10449@n2100.arm.linux.org.uk> <20100122164713.GA21907@shareable.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Received: from caramon.arm.linux.org.uk ([78.32.30.218]:56545 "EHLO caramon.arm.linux.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754838Ab0AVQ5k (ORCPT ); Fri, 22 Jan 2010 11:57:40 -0500 Content-Disposition: inline In-Reply-To: <20100122164713.GA21907@shareable.org> Sender: linux-serial-owner@vger.kernel.org List-Id: linux-serial@vger.kernel.org To: Jamie Lokier Cc: Valentin Longchamp , "linux-arm-kernel@lists.infradead.org" , "s.hauer@pengutronix.de" , Wolfram Sang , "linux-serial@vger.kernel.org" On Fri, Jan 22, 2010 at 04:47:13PM +0000, Jamie Lokier wrote: > Any tips on how to make the serial receive irq latency more reliable > on ARM, with a boringly generic serial driver? What you could do is arrange for a backtrace to be printed when you read an overrun condition from the UART - if interrupts were disabled by something taking a long time, and then enabled, you should see the point where they were just enabled in the backtrace. It could be down to another IRQF_DISABLED interrupt - in which case you won't see it in the backtrace. Of course, printing a backtrace will cause subsequent overruns...