From mboxrd@z Thu Jan 1 00:00:00 1970 From: LW@KARO-electronics.de (=?utf-8?Q?Lothar_Wa=C3=9Fmann?=) Date: Mon, 30 Sep 2013 13:06:34 +0200 Subject: imprecise external abort using the flexcan driver on i.MX6Q In-Reply-To: <5245E2C5.1030705@pengutronix.de> References: <21060.15934.600859.167074@ipc1.ka-ro> <524455FD.7070808@pengutronix.de> <20130926155422.GQ12758@n2100.arm.linux.org.uk> <21061.21191.197931.54061@ipc1.ka-ro> <5245E2C5.1030705@pengutronix.de> Message-ID: <21065.23354.418805.871480@ipc1.ka-ro> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org Hi, Marc Kleine-Budde writes: > On 09/27/2013 07:24 PM, Matt Sealey wrote: > > Marc - I don't think FLEXCAN has changed layout at all in these areas. > > The hardware always worked this way.. > > All flexcan cores support the RX FIFO, the mx6 supports an additional > mode for different acceptance filters. > > > The only difference here is that the i.MX53 is doing something weird > > on the bus. The i.MX6Q is giving the absolutely correct BRESP for the > > transfer to the peripheral (in effect, a "go away, this is my data" > > failure, which the CPU turns into an imprecise abort since it no idea > > which transaction it committed aeons ago caused it). > > > > Writes to 0x90 to 0xDF while MCR[FEN] is set *should* cause a data > > abort.. because it's not even a read-only region, it *should* be > > totally inaccessible to the CPU. > > > > The question I have is, when MCR[FEN] is set on i.MX53, does reading > > from those reserved registers give anything but 0's or garbage? I'm > > curious, that's all, it doesn't really matter ;) > > The driver only read from message buffer 0, and uses buffer 8 for tx. > The others are not accessed, unless in that chip start routine. We don't > need this loop, it comes from the original driver. I think no one has > ever noticed that bug, because all other CPUs have not complained. > > The driver without the loop is working on mx6 and Lothar is testing it > on mx53. > I can confirm, that the driver still works on i.MX53 as before the patch. Is someone going to prepare a patch, or should I do it, as I was the one who first brought up this issue? Lothar Wa?mann -- ___________________________________________________________ Ka-Ro electronics GmbH | Pascalstra?e 22 | D - 52076 Aachen Phone: +49 2408 1402-0 | Fax: +49 2408 1402-10 Gesch?ftsf?hrer: Matthias Kaussen Handelsregistereintrag: Amtsgericht Aachen, HRB 4996 www.karo-electronics.de | info at karo-electronics.de ___________________________________________________________