From mboxrd@z Thu Jan 1 00:00:00 1970 Return-path: Received: from metis.ext.pengutronix.de ([2001:6f8:1178:4:290:27ff:fe1d:cc33]) by bombadil.infradead.org with esmtps (Exim 4.80.1 #2 (Red Hat Linux)) id 1YH8Lj-0002k8-D4 for barebox@lists.infradead.org; Fri, 30 Jan 2015 09:58:52 +0000 Received: from kiwi.hi.pengutronix.de ([2001:67c:670:100:1d::c3] helo=kiwi) by metis.ext.pengutronix.de with esmtp (Exim 4.72) (envelope-from ) id 1YH8LM-00085H-8U for barebox@lists.infradead.org; Fri, 30 Jan 2015 10:58:28 +0100 Received: from jlu by kiwi with local (Exim 4.84) (envelope-from ) id 1YH8LM-0004Z1-06 for barebox@lists.infradead.org; Fri, 30 Jan 2015 10:58:28 +0100 Message-ID: <1422611907.12367.12.camel@pengutronix.de> From: Jan =?ISO-8859-1?Q?L=FCbbe?= Date: Fri, 30 Jan 2015 10:58:27 +0100 In-Reply-To: <20150130074017.GP12209@pengutronix.de> References: <20150129091229.GA424@gmail.com> <20150129092151.GE12209@pengutronix.de> <87k305o0cd.fsf@free.fr> <20150130074017.GP12209@pengutronix.de> Mime-Version: 1.0 List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "barebox" Errors-To: barebox-bounces+u.kleine-koenig=pengutronix.de@lists.infradead.org Subject: Re: Access to first 0x1000 byte on imx53/imx6 To: barebox@lists.infradead.org On Fr, 2015-01-30 at 08:40 +0100, Sascha Hauer wrote: > On Thu, Jan 29, 2015 at 08:25:54PM +0100, Robert Jarzmik wrote: > > Sascha Hauer writes: > > > > > On Thu, Jan 29, 2015 at 10:12:46AM +0100, Wjatscheslaw Stoljarski > wrote: > > >> Hello, > > >> > > >> If I try to read from first 4k RAM on imx53/imx6, with md or from > code, > > >> barebox show stacktrace with mesage: > > >> "unable to handle NULL pointer dereference at address 0x...". > > >> Is it possible in some way do that? > > > > > > The only way I know is to disable CONFIG_MMU in the config. > > I think the solution in arch/arm/boards/mioa701/board.c (remapping > the 0x0 > > address) should work here : > > docg3_iospace = map_io_sections(0x0, (void *)0xe0000000, > 0x2000); > > We could create a /dev/zeropage with the code above. That would make > the zero page generally available. I don't know if this is worth the > effort though. Couldn't we special-case the zero page in /dev/mem instead? Regards, Jan -- Pengutronix e.K. | | Industrial Linux Solutions | http://www.pengutronix.de/ | Peiner Str. 6-8, 31137 Hildesheim, Germany | Phone: +49-5121-206917-0 | Amtsgericht Hildesheim, HRA 2686 | Fax: +49-5121-206917-5555 | _______________________________________________ barebox mailing list barebox@lists.infradead.org http://lists.infradead.org/mailman/listinfo/barebox