Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753309AbaA2S1K (ORCPT ); Wed, 29 Jan 2014 13:27:10 -0500 Received: from mail-wg0-f50.google.com ([74.125.82.50]:38861 "EHLO mail-wg0-f50.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752369AbaA2S1I (ORCPT ); Wed, 29 Jan 2014 13:27:08 -0500 Date: Wed, 29 Jan 2014 18:28:05 +0000 From: Leif Lindholm To: Will Deacon Cc: "linux-kernel@vger.kernel.org" , "grant.likely@secretlab.ca" , "linux-efi@vger.kernel.org" , "linux@arm.linux.org.uk" , "patches@linaro.org" , "roy.franz@linaro.org" , "matt.fleming@intel.com" , "msalter@redhat.com" , "linux-arm-kernel@lists.infradead.org" Subject: Re: [PATCH v4 2/5] arm: add new asm macro update_sctlr Message-ID: <20140129182805.GF11329@bivouac.eciton.net> References: <1389445524-30623-1-git-send-email-leif.lindholm@linaro.org> <1389445524-30623-3-git-send-email-leif.lindholm@linaro.org> <20140122112055.GF1621@mudshark.cambridge.arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20140122112055.GF1621@mudshark.cambridge.arm.com> 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, Jan 22, 2014 at 11:20:55AM +0000, Will Deacon wrote: > > +#ifdef CONFIG_CPU_CP15 > > +/* Macro for setting/clearing bits in sctlr */ > > + .macro update_sctlr, set:req, clear:req, tmp:req, tmp2:req > > + mrc p15, 0, \tmp, c1, c0, 0 > > + ldr \tmp2, =\set > > + orr \tmp, \tmp, \tmp2 > > + ldr \tmp2, =\clear > > + mvn \tmp2, \tmp2 > > + and \tmp, \tmp, \tmp2 > > + mcr p15, 0, \tmp, c1, c0, 0 > > I think this would be cleaner if you force the caller to put set and clear > into registers beforehand, rather than have to do the literal load every > time. Also, I don't think set and clear should be required (and then you can > lose tmp2 as well). I can't figure out how to make register-parameters non-required (i.e. conditionalise on whether an optional parameter was provided), so my attempt of refactoring actually ends up using an additional register: #ifdef CONFIG_CPU_CP15 /* Macro for setting/clearing bits in sctlr */ .macro update_sctlr, set:req, clear:req, tmp:req mrc p15, 0, \tmp, c1, c0, 0 orr \tmp, \set mvn \clear, \clear and \tmp, \tmp, \clear mcr p15, 0, \tmp, c1, c0, 0 .endm #endif If you think that's an improvement I can do that, and I have (just) enough registers to spare. If I'm being daft with my macro issues, do point it out. / Leif -- 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/