Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753443Ab3CUVQT (ORCPT ); Thu, 21 Mar 2013 17:16:19 -0400 Received: from mail.free-electrons.com ([94.23.35.102]:56559 "EHLO mail.free-electrons.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753152Ab3CUVQS (ORCPT ); Thu, 21 Mar 2013 17:16:18 -0400 Date: Thu, 21 Mar 2013 22:16:13 +0100 From: Thomas Petazzoni To: Andrew Lunn Cc: Gregory CLEMENT , Jason Cooper , Grant Likely , Rob Herring , Ezequiel Garcia , linux-arm-kernel@lists.infradead.org, devicetree-discuss@lists.ozlabs.org, linux-kernel@vger.kernel.org, Arnd Bergmann , Olof Johansson , Nicolas Pitre , Lior Amsalem , Maen Suleiman , Tawfik Bayouk , Shadi Ammouri , Eran Ben-Avi , Yehuda Yitschak , Nadav Haklai , Ike Pan , Chris Van Hoof , Dan Frazier , Leif Lindholm , Jon Masters , David Marlin , Sebastian Hesselbarth Subject: Re: [PATCH 5/5] arm: dts: Convert mvebu device tree files to 64 bits Message-ID: <20130321221613.53a48845@skate> In-Reply-To: <20130321203751.GP21478@lunn.ch> References: <1363883179-1361-1-git-send-email-gregory.clement@free-electrons.com> <1363883179-1361-6-git-send-email-gregory.clement@free-electrons.com> <20130321201533.GN21478@lunn.ch> <20130321212236.1015295d@skate> <20130321203751.GP21478@lunn.ch> Organization: Free Electrons X-Mailer: Claws Mail 3.9.0 (GTK+ 2.24.10; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1029 Lines: 28 Dear Andrew Lunn, On Thu, 21 Mar 2013 21:37:51 +0100, Andrew Lunn wrote: > > And I'm not sure the SDRAM address decoding windows allows to split the > > first 4 GB of RAM into two areas, one that would be mapped starting at > > physical address 0x0, and another area that would be mapped at a > > different address (above 4 GB). > > So why not map the whole SDRAM above 4GB physical address? As Lior rightly pointed out to me, this would prevent any device from DMA-ing to or from the RAM. Devices can only access the first 32 bits of the physical address space. So there must be some RAM below 4 GB. Best regards, Thomas -- Thomas Petazzoni, Free Electrons Kernel, drivers, real-time and embedded Linux development, consulting, training and support. http://free-electrons.com -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/