From mboxrd@z Thu Jan 1 00:00:00 1970 From: Viktor Babrian Subject: Re: [PATCH 3.19-rc3] c_can: SIE disabled when berr-reporting is off to reduce irq flood Date: Sun, 18 Jan 2015 19:52:56 +0100 (CET) Message-ID: References: <9c72f211-becc-4c0f-94f6-0700dfb1195e@GRBSR0089.marel.net> <1735533.0yOonAfCy1@heinz> <54B472B2.4010300@optusnet.com.au> <20150113153243.26859.47218@shannon> <54BBFCAF.2090603@pengutronix.de> Mime-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII; format=flowed Return-path: Received: from mx1.renyi.hu ([193.224.79.18]:37869 "EHLO smtp.renyi.hu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751081AbbARSxG (ORCPT ); Sun, 18 Jan 2015 13:53:06 -0500 In-Reply-To: <54BBFCAF.2090603@pengutronix.de> Sender: linux-can-owner@vger.kernel.org List-ID: To: Marc Kleine-Budde Cc: Viktor Babrian , Andri Yngvason , Tom Evans , linux-can@vger.kernel.org > NACK. The transitions are important for some applications. I've an not > yet mainlined series that limits the bus errors. I'm going to port them > to the current kernel tomorrow. Can you test it? This controller simply does not have a warn->pass state transition interrupt. The only way to accurately (right on time) report this transition is to switch on all error interrupts (ie the status interrupt) that cause interrupt flood in some scenarios e.g. when frame is not acked by other parties. If we don't turn on the status interrupt, the warn->pass state transition can be detected later on a successful rx/tx event (or when entering bus off etc). I have learned that the warn->pass transition interrupt is also missing from other controllers as well (like Flexcan). Interrupt flood caused by enabling error interrupts regardless of the berr-reporting state is an issue there too. Also note that when the system is flooded by these error interrupts, system performace degrades so much that serial terminal echo becomes annoyingly long. When this happens, I wonder how usable the "accurate" state transition reports are anyway. Regards, Viktor