Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932866AbbLHMtk (ORCPT ); Tue, 8 Dec 2015 07:49:40 -0500 Received: from mail-wm0-f49.google.com ([74.125.82.49]:37073 "EHLO mail-wm0-f49.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933489AbbLHMs5 (ORCPT ); Tue, 8 Dec 2015 07:48:57 -0500 Date: Tue, 8 Dec 2015 12:48:54 +0000 From: Matt Fleming To: Ard Biesheuvel Cc: linux-efi@vger.kernel.org, Alexandre Belloni , linux-kernel@vger.kernel.org, Thomas Gleixner , rtc-linux@googlegroups.com Subject: Re: [PATCH v2 6/7] efi: runtime-wrapper: get rid of the rtc_lock spinlock Message-ID: <20151208124854.GC2518@codeblueprint.co.uk> References: <1448967020-20190-1-git-send-email-ard.biesheuvel@linaro.org> <1448967020-20190-7-git-send-email-ard.biesheuvel@linaro.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1448967020-20190-7-git-send-email-ard.biesheuvel@linaro.org> User-Agent: Mutt/1.5.24 (2015-08-30) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1165 Lines: 24 On Tue, 01 Dec, at 11:50:19AM, Ard Biesheuvel wrote: > The rtc_lock spinlock aims to serialize access to the CMOS RTC between > the UEFI firmware and the kernel drivers that use it directly. However, > x86 is the only arch that performs such direct accesses, and that never > uses the time related UEFI runtime services. Since no other UEFI enlightened > architectures have a legcay CMOS RTC anyway, we can remove the rtc_lock > spinlock entirely. > > Signed-off-by: Ard Biesheuvel > --- > drivers/firmware/efi/runtime-wrappers.c | 32 +++++--------------- > 1 file changed, 8 insertions(+), 24 deletions(-) Is this really true? It's not possible, for instance, for 32-bit ARM systems to use the rtc-cmos driver which would access the same physical device that UEFI would with the GetTime() service? With the pending 32-bit ARM UEFI support coming, this needs to be considered carefully. -- 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/