Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758820Ab3DYQCD (ORCPT ); Thu, 25 Apr 2013 12:02:03 -0400 Received: from mail-wg0-f54.google.com ([74.125.82.54]:52591 "EHLO mail-wg0-f54.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757164Ab3DYQCB (ORCPT ); Thu, 25 Apr 2013 12:02:01 -0400 MIME-Version: 1.0 In-Reply-To: <5178D719.2060405@ahsoftware.de> References: <517746E4.908@linaro.org> <51774F44.2060704@linaro.org> <517769A9.5060308@ahsoftware.de> <51780348.6090202@linaro.org> <5178D719.2060405@ahsoftware.de> From: Kay Sievers Date: Thu, 25 Apr 2013 18:01:39 +0200 Message-ID: Subject: Re: CONFIG_RTC_HCTOSYS lost on x86 with ALWAYS_USE_PERSISTENT_CLOCK changes? To: Alexander Holler Cc: John Stultz , LKML , Feng Tang , Jason Gunthorpe Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1185 Lines: 32 On Thu, Apr 25, 2013 at 9:11 AM, Alexander Holler wrote: > Hmm, I thought RTC_SYSTOHC was there to update the used RTC clock with the > time from NTP (and liked that). That seems to have the nice self-explaining name CONFIG_GENERIC_CMOS_UPDATE. :) > Therefor I don't understand why it is > redundant and unnecessary on x86. Because the x86 native RTC/cmos is updated with platform code, not generic rtc code: arch/x86/kernel/rtc.c > Of course, most systems do have something > in userspace to set the RTC on shutdown, so it isn't really needed. That is gone on most systems today. Systems without NTP or something else running have no clue about the time, and should not touch the hardware clock with a boot cycle. Only if a reliable time source like NTP is available, it should update the hardware clock accordingly. > Anyway, thanks a lot for the great overview. Yeah, thanks John, from my side too. Kay -- 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/