From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-2.3 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id EDE1CC32751 for ; Wed, 7 Aug 2019 17:08:14 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id C499B2235C for ; Wed, 7 Aug 2019 17:08:14 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2388814AbfHGRIN (ORCPT ); Wed, 7 Aug 2019 13:08:13 -0400 Received: from foss.arm.com ([217.140.110.172]:52162 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729278AbfHGRIN (ORCPT ); Wed, 7 Aug 2019 13:08:13 -0400 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 3C10F344; Wed, 7 Aug 2019 10:08:12 -0700 (PDT) Received: from e107155-lin (e107155-lin.cambridge.arm.com [10.1.196.42]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 8AEBD3F575; Wed, 7 Aug 2019 10:08:11 -0700 (PDT) Date: Wed, 7 Aug 2019 18:08:09 +0100 From: Sudeep Holla To: David Laight Cc: "linux-arm-kernel@lists.infradead.org" , "linux-kernel@vger.kernel.org" , Philipp Zabel Subject: Re: [PATCH] firmware: arm_scmi: Use {get,put}_unaligned_le32 accessors Message-ID: <20190807170808.GD27278@e107155-lin> References: <20190807130038.26878-1-sudeep.holla@arm.com> <4102ce79ef7a4f5ba819663d072bccc8@AcuMS.aculab.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <4102ce79ef7a4f5ba819663d072bccc8@AcuMS.aculab.com> User-Agent: Mutt/1.9.4 (2018-02-28) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Aug 07, 2019 at 03:18:59PM +0000, David Laight wrote: > From: Sudeep Holla > > Sent: 07 August 2019 14:01 > > > > Instead of type-casting the {tx,rx}.buf all over the place while > > accessing them to read/write __le32 from/to the firmware, let's use > > the nice existing {get,put}_unaligned_le32 accessors to hide all the > > type cast ugliness. > > Why the 'unaligned' accessors? > Since the firmware run in LE, we do byte-swapping anyways. > > - *(__le32 *)t->tx.buf = cpu_to_le32(id); > > + put_unaligned_le32(id, t->tx.buf); > If you look at the generic definition for put_unaligned_le32, it's exactly the same as what I am replacing with the call. So nothing changes IIUC. In fact, I see that all the helper in unaligned/access_ok.h just do the byte-swapping. > These will be expensive if the cpu doesn't support them. The SCMI is currently used only on ARM platforms which have HAVE_EFFICIENT_UNALIGNED_ACCESS defined. -- Regards, Sudeep