From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756151Ab2GXTYe (ORCPT ); Tue, 24 Jul 2012 15:24:34 -0400 Received: from moutng.kundenserver.de ([212.227.17.9]:57141 "EHLO moutng.kundenserver.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755995Ab2GXTYb (ORCPT ); Tue, 24 Jul 2012 15:24:31 -0400 From: Arnd Bergmann To: Catalin Marinas Subject: Re: [08/36] AArch64: Kernel booting and initialisation Date: Tue, 24 Jul 2012 18:53:16 +0000 User-Agent: KMail/1.12.2 (Linux/3.5.0-rc1+; KDE/4.3.2; x86_64; ; ) Cc: Christopher Covington , Stephen Warren , "linux-kernel@vger.kernel.org" , Will Deacon , Domenico Andreoli References: <1341608777-12982-9-git-send-email-catalin.marinas@arm.com> <500DB986.7090309@codeaurora.org> <20120724162404.GB29519@arm.com> In-Reply-To: <20120724162404.GB29519@arm.com> MIME-Version: 1.0 Content-Type: Text/Plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit Message-Id: <201207241853.16625.arnd@arndb.de> X-Provags-ID: V02:K0:Y7Uog3QdL34VpCiL955gokT5gSHJCOxGjHYvtvgv1C2 p05ThIiKVqrWlc5iVC7WdBSqxTdJxqMuwLMdjiudYRiITFpTun t4KihJwpaoD2aaZJ0tFC//fIRObpyeJJIjWnFIojwplMJqtaYy LLp1B2oZdqZ1gwckbHP8ELBQKFIn/uvPl4lxZxYJhoTvqOjXOx nmd1yc2Pyz8T1QAsle8n0ucF5Y4yTPNP5R3SxBEdfjYV6KF6fG Bp6fFqipUSohD6jlAEsebfflq/nxQW0Mkcq32D65Z+IOU6fQYD E4m9SYAlSRz3DMBVS20hpvJ3n2oMv16XegaJXktwowfKcl0Uv0 L1Q7LD2SLqYFuTDovRUA= Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tuesday 24 July 2012, Catalin Marinas wrote: > On Mon, Jul 23, 2012 at 09:52:22PM +0100, Christopher Covington wrote: > > Hi Catalin and Stephen, > > > > Catalin Marinas - July 8, 2012, 9:18 a.m. > > > On Fri, Jul 06, 2012 at 10:32:54PM +0100, Stephen Warren wrote: > > > > > >> Also, on Tegra at least and perhaps OMAP too, there are a few parts > > >> of earlyprintk serial port setup (i.e. port selection) which happen > > >> as part of the decompressor rather than the main kernel image, so > > >> we'd have to re-jig that too. > > > > > > Whatever we did on AArch32, if it was useful and we want to follow a > > > similar model it needs porting given that the code cannot be shared. So > > > there is nothing to re-jig but rather implement. > > > > > > As for earlyprintk, you can initialise it in the decompressed kernel > > > anyway. But even though it's a useful debugging tool, it goes against > > > the single Image aim (at least the current printascii/addruart > > > implementation). I don't have a proper implementation yet. > > > > Would DCC [1] be a reasonably commonly available early printk mechanism > > for the single image to provide? > > Yes, this can be implemented but I think it has its own restrictions, > requiring a JTAG connection. Right, which means that it's not generic and we still need to make a decision for a how we want to solve the underlying problem. The options I see are: 1. Have no earlyprintk before loading the console drivers 2. Make the series from Domenico architecture independent code 3. Reimplement a layer like that, differently 4. Make it a compile-time option and allow this only for low level debugging purposes but disable it in distro kernels. Arnd