From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753190Ab3FZVeX (ORCPT ); Wed, 26 Jun 2013 17:34:23 -0400 Received: from mail-wi0-f173.google.com ([209.85.212.173]:38775 "EHLO mail-wi0-f173.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753053Ab3FZVeW (ORCPT ); Wed, 26 Jun 2013 17:34:22 -0400 Date: Wed, 26 Jun 2013 23:34:10 +0200 From: Leif Lindholm To: Arnd Bergmann Cc: linux-arm-kernel@lists.infradead.org, nico@linaro.org, patches@linaro.org, linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org, Russell King - ARM Linux Subject: Re: [PATCH 0/2] arm: add early_ioremap() support Message-ID: <20130626213409.GA18151@rocoto.smurfnet.nu> References: <1372182401-11029-1-git-send-email-leif.lindholm@linaro.org> <201306262052.09640.arnd@arndb.de> <20130626192352.GE9078@rocoto.smurfnet.nu> <201306262323.50691.arnd@arndb.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <201306262323.50691.arnd@arndb.de> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Jun 26, 2013 at 11:23:50PM +0200, Arnd Bergmann wrote: > > Is this an issue here, since (unlike x86) this early_ioremap only works > > before paging_init()? > > The main problem is that the total fixmap size is only around 900kb, > and we want to reserve at least 64kb per cpu for kmap_atomic. > If you want to fit multiple 128kb mappings in there, you run out of > space really fast. Sorry, I still don't get it. Are you saying that kmap_atomic is available before kmap_init() (in paging_init())? If not, all of my mappings are discarded (well, abandoned to be more correct), so I don't see how it affects kmap. > > > Extending the iotable mechanism on ARM would be the convenient > > > solution for us I think. > > > > Could that easily be extended to give similar semantics sufficiently > > that we can progress with merging more of the UEFI and ACPI support > > together as common code with x86/ia64? > > I don't know what the requirements are, but the idea with iotable > is that the mappings stay around at run time, while it seems you want > to discard them at some point. Indeed - almost immediately. x86 early_ioremap can coexist with kmap; the intent of my implementation is to use the kmap region only before kmap is available. / Leif