From mboxrd@z Thu Jan 1 00:00:00 1970 From: David Jander Subject: Re: [PATCH 1/3] can: flexcan.c: Correctly initialize mailboxes Date: Tue, 2 Sep 2014 12:37:25 +0200 Message-ID: <20140902123725.01808f36@archvile> References: <1409133487-23367-1-git-send-email-david@protonic.nl> <1409133487-23367-2-git-send-email-david@protonic.nl> <54059ADC.60309@pengutronix.de> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Return-path: Received: from protonic.xs4all.nl ([83.163.252.89]:5124 "EHLO protonic.xs4all.nl" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751180AbaIBKhN (ORCPT ); Tue, 2 Sep 2014 06:37:13 -0400 In-Reply-To: <54059ADC.60309@pengutronix.de> Sender: linux-can-owner@vger.kernel.org List-ID: To: Marc Kleine-Budde Cc: wg@grandegger.com, linux-can@vger.kernel.org On Tue, 02 Sep 2014 12:24:28 +0200 Marc Kleine-Budde wrote: > On 08/27/2014 11:58 AM, David Jander wrote: > > Apparently mailboxes may contain random data at startup, causing some of > > them being prepared for message reception. This causes overruns being > > missed or even confusing the IRQ check for trasmitted messages, increasing > > the transmit counter instead of the error counter. > > > > Signed-off-by: David Jander > > Before patch > > 0d1862e can: flexcan: fix flexcan_chip_start() on imx6 > > there was a loop clearing the whole cantxfg register space. But this > turned out to be bogus, as message buffers 1...7 are reserved by the > FIFO engine and we're not allowed to tough them. This lead to some kind > of abort on imx6. > > You may need this patch once you don't make use of the FIFO engine any more. You will need this patch in either case, but indeed, if you use the FIFO, you should skip the MB's that are shadowed by the FIFO. If you don't clear the rest of the MB's they may still contain random data and the problem remains. IMHO 0d1862e is wrong, since buffers are not in reset default values. There is no indication of that in the reference manual, and I have observed that they are indeed not cleared after reset. Best regards, -- David Jander Protonic Holland.