From patchwork Fri May 24 15:43:56 2013 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Javi Merino X-Patchwork-Id: 2611931 Return-Path: X-Original-To: patchwork-linux-arm@patchwork.kernel.org Delivered-To: patchwork-process-083081@patchwork1.kernel.org Received: from casper.infradead.org (casper.infradead.org [85.118.1.10]) by patchwork1.kernel.org (Postfix) with ESMTP id EDB423FD4E for ; Fri, 24 May 2013 16:13:06 +0000 (UTC) Received: from merlin.infradead.org ([2001:4978:20e::2]) by casper.infradead.org with esmtps (Exim 4.80.1 #2 (Red Hat Linux)) id 1UfuCo-0006Yr-Rq; Fri, 24 May 2013 15:46:59 +0000 Received: from localhost ([::1] helo=merlin.infradead.org) by merlin.infradead.org with esmtp (Exim 4.80.1 #2 (Red Hat Linux)) id 1UfuBI-0002AP-1t; Fri, 24 May 2013 15:45:24 +0000 Received: from service87.mimecast.com ([91.220.42.44]) by merlin.infradead.org with esmtp (Exim 4.80.1 #2 (Red Hat Linux)) id 1UfuBA-00029P-S7 for linux-arm-kernel@lists.infradead.org; Fri, 24 May 2013 15:45:18 +0000 Received: from cam-owa2.Emea.Arm.com (fw-tnat.cambridge.arm.com [217.140.96.21]) by service87.mimecast.com; Fri, 24 May 2013 16:44:52 +0100 Received: from e102654-lin.cambridge.arm.com ([10.1.255.212]) by cam-owa2.Emea.Arm.com with Microsoft SMTPSVC(6.0.3790.3959); Fri, 24 May 2013 16:44:50 +0100 Received: by e102654-lin.cambridge.arm.com (sSMTP sendmail emulation); Fri, 24 May 2013 16:44:50 +0100 From: Javi Merino To: linux-arm-kernel@lists.infradead.org, linux-doc@vger.kernel.org Subject: [PATCH] ARM: document the bigger pagetables needed for LPAE Date: Fri, 24 May 2013 16:43:56 +0100 Message-Id: <1369410236-22398-1-git-send-email-javi.merino@arm.com> X-Mailer: git-send-email 1.7.9.5 X-OriginalArrivalTime: 24 May 2013 15:44:50.0584 (UTC) FILETIME=[A076E180:01CE5895] X-MC-Unique: 113052416445204501 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20130524_114517_101704_58251BDC X-CRM114-Status: GOOD ( 13.75 ) X-Spam-Score: -2.6 (--) X-Spam-Report: SpamAssassin version 3.3.2 on merlin.infradead.org summary: Content analysis details: (-2.6 points) pts rule name description ---- ---------------------- -------------------------------------------------- -0.7 RCVD_IN_DNSWL_LOW RBL: Sender listed at http://www.dnswl.org/, low trust [91.220.42.44 listed in list.dnswl.org] -0.0 SPF_PASS SPF: sender matches SPF record -1.9 BAYES_00 BODY: Bayes spam probability is 0 to 1% [score: 0.0000] Cc: Javi Merino , rob@landley.net X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , MIME-Version: 1.0 Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+patchwork-linux-arm=patchwork.kernel.org@lists.infradead.org The Booting documentation assumes that the initial pagetables are 16KiB but since 1b6ba46 (ARM: LPAE: MMU setup for the 3-level page table format) they are 20KiB for LPAE kernels. Thus, the recommendation to put atags or the dtb in the first 16KiB is wrong, there's only 12KiB of space there in LPAE kernels, so update the documentation accordingly. --- Documentation/arm/Booting | 9 +++++---- 1 file changed, 5 insertions(+), 4 deletions(-) diff --git a/Documentation/arm/Booting b/Documentation/arm/Booting index 0c1f475..f6f9cd8 100644 --- a/Documentation/arm/Booting +++ b/Documentation/arm/Booting @@ -105,7 +105,7 @@ The tagged list should be stored in system RAM. The tagged list must be placed in a region of memory where neither the kernel decompressor nor initrd 'bootp' program will overwrite -it. The recommended placement is in the first 16KiB of RAM. +it. The recommended placement is in the first 12KiB of RAM. 4b. Setup the device tree ------------------------- @@ -120,7 +120,7 @@ tagged list. The boot loader must pass at a minimum the size and location of the system memory, and the root filesystem location. The dtb must be placed in a region of memory where the kernel decompressor will not -overwrite it. The recommended placement is in the first 16KiB of RAM +overwrite it. The recommended placement is in the first 12KiB of RAM with the caveat that it may not be located at physical address 0 since the kernel interprets a value of 0 in r2 to mean neither a tagged list nor a dtb were passed. @@ -137,8 +137,9 @@ then it is legal for the boot loader to call the zImage in flash directly. The zImage may also be placed in system RAM (at any location) and -called there. Note that the kernel uses 16K of RAM below the image -to store page tables. The recommended placement is 32KiB into RAM. +called there. Note that the kernel may use up to 20KiB of RAM below +the image to store page tables. The recommended placement is 32KiB +into RAM. In either case, the following conditions must be met: