From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1761063Ab1D3Ah2 (ORCPT ); Fri, 29 Apr 2011 20:37:28 -0400 Received: from mail-vx0-f174.google.com ([209.85.220.174]:51540 "EHLO mail-vx0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1761042Ab1D3Ah1 (ORCPT ); Fri, 29 Apr 2011 20:37:27 -0400 Date: Fri, 29 Apr 2011 20:37:24 -0400 (EDT) From: Nicolas Pitre X-X-Sender: nico@xanadu.home To: Grant Likely cc: devicetree-discuss@lists.ozlabs.org, linux-arm-kernel@lists.infradead.org, Russell King , lkml Subject: Re: [PATCH v5 8/8] dt: add documentation of ARM dt boot interface In-Reply-To: <20110429071608.12522.7764.stgit@ponder> Message-ID: References: <20110429070135.12522.35745.stgit@ponder> <20110429071608.12522.7764.stgit@ponder> User-Agent: Alpine 2.00 (LFD 1167 2008-08-23) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, 29 Apr 2011, Grant Likely wrote: > diff --git a/Documentation/devicetree/booting-without-of.txt b/Documentation/devicetree/booting-without-of.txt > index 50619a0..31d7e8a 100644 > --- a/Documentation/devicetree/booting-without-of.txt > +++ b/Documentation/devicetree/booting-without-of.txt [...] > +1) Entry point for arch/arm > +--------------------------- > + > + There is one single entry point to the kernel, at the start > + of the kernel image. That entry point supports two calling > + conventions. A summary of the interface is described here. A full > + description of the boot requirements is documented in > + Documentation/arm/Booting > + > + a) ATAGS interface. Minimal information is passed from firmware > + to the kernel with a tagged list of predefined parameters. > + > + r0 : 0 > + > + r1 : Machine type number > + > + r2 : Physical address of tagged list in system RAM > + > + b) Entry with a flattened device-tree block. Firmware loads the > + physical address of the flattened device tree block (dtb) into r2, > + r1 is not used, but it is considered good practise to use a valid > + machine number as described in Documentation/arm/Booting. > + > + r0 : 0 > + > + r1 : Valid machine type number. When using a device tree, > + a single machine type number will often be assigned to > + represent a class or family of SoCs. > + > + r2 : physical pointer to the device-tree block > + (defined in chapter II) in RAM. Device tree can be located > + anywhere in system RAM, but it should be aligned on a 64 bit > + boundary. > + > + The kernel will differentiate between ATAGS and device tree booting by > + reading the memory pointed to by r1 and looking for either the flattened s/r1/r2/ Nicolas