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_2 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 947C0C32792 for ; Thu, 3 Oct 2019 13:14:59 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 74D26215EA for ; Thu, 3 Oct 2019 13:14:59 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730337AbfJCNO6 (ORCPT ); Thu, 3 Oct 2019 09:14:58 -0400 Received: from mail-out.m-online.net ([212.18.0.10]:40089 "EHLO mail-out.m-online.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726508AbfJCNO6 (ORCPT ); Thu, 3 Oct 2019 09:14:58 -0400 Received: from frontend01.mail.m-online.net (unknown [192.168.8.182]) by mail-out.m-online.net (Postfix) with ESMTP id 46kYQ73LN2z1rpSZ; Thu, 3 Oct 2019 15:14:55 +0200 (CEST) Received: from localhost (dynscan1.mnet-online.de [192.168.6.70]) by mail.m-online.net (Postfix) with ESMTP id 46kYQ72G6Nz1qqkM; Thu, 3 Oct 2019 15:14:55 +0200 (CEST) X-Virus-Scanned: amavisd-new at mnet-online.de Received: from mail.mnet-online.de ([192.168.8.182]) by localhost (dynscan1.mail.m-online.net [192.168.6.70]) (amavisd-new, port 10024) with ESMTP id qyrIp-v7WbMQ; Thu, 3 Oct 2019 15:14:54 +0200 (CEST) X-Auth-Info: xiZETJUVqfKpf2L5V7ri6d768Sag1oWyEMv8K/uuf50= Received: from jawa (85-222-111-42.dynamic.chello.pl [85.222.111.42]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.mnet-online.de (Postfix) with ESMTPSA; Thu, 3 Oct 2019 15:14:54 +0200 (CEST) Date: Thu, 3 Oct 2019 15:14:34 +0200 From: Lukasz Majewski To: Alexandre Belloni Cc: Alessandro Zummo , linux-rtc@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] rtc: Add support for century bits to m41t62 (rv4162) RTC devices Message-ID: <20191003151434.49762715@jawa> In-Reply-To: <20191003123538.GS4106@piout.net> References: <20190911154803.15969-1-lukma@denx.de> <20191003114831.GR4106@piout.net> <20191003142150.3d73a9d7@jawa> <20191003123538.GS4106@piout.net> Organization: denx.de X-Mailer: Claws Mail 3.17.4 (GTK+ 2.24.32; x86_64-pc-linux-gnu) MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha512; boundary="Sig_/j/.C7KS_WRAAcH/i3tvI2vT"; protocol="application/pgp-signature" Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org --Sig_/j/.C7KS_WRAAcH/i3tvI2vT Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: quoted-printable Hi Alexandre, > On 03/10/2019 14:21:50+0200, Lukasz Majewski wrote: > > >=20 > > > See the datasheet: > > >=20 > > > "During any year which is a multiple of 4, the RV-4162 RTC will > > > automatically insert leap day, February 29. Therefore, the > > > application software must correct for this during the exception > > > years (2100, 2200, etc.) as noted above." =20 > >=20 > > I'm wondering what the phrase "application software" means here? > >=20 > > If it is the userland SW, then we shall at least be able to set > > 2099 in this device and then count on software correction. > >=20 > > If the "application software" is the kernel driver - the date > > correction shall be done there (maybe some lookup table?). > >=20 > > Personally, I do prefer the first option - this means that with this > > patch we can set the time to e.g. 2234 year and then rely on > > userland software (or libc) to do the correction. > > =20 >=20 > It is not possible to ensure this correction is properly done in > software, there is no point in letting the user set those bits. >=20 >=20 I see your point. However, could you share your idea on testing setting RTC time to year 2100 on this particular IC (by using hctosys and friends)? Best regards, Lukasz Majewski -- DENX Software Engineering GmbH, Managing Director: Wolfgang Denk HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany Phone: (+49)-8142-66989-59 Fax: (+49)-8142-66989-80 Email: lukma@denx.de --Sig_/j/.C7KS_WRAAcH/i3tvI2vT Content-Type: application/pgp-signature Content-Description: OpenPGP digital signature -----BEGIN PGP SIGNATURE----- iQEzBAEBCgAdFiEEgAyFJ+N6uu6+XupJAR8vZIA0zr0FAl2V9DoACgkQAR8vZIA0 zr3BIQgAlkA+YDvGJVBeIvlyQeEpjCBRSOKg1njJc/zbo+dyLX04exb85bLdZaZa /qdn/Haxk7CAh6I+vL8X57hcmdJSLBtev42HWSnIYlL8jabaU0SMm0s8kPFln3Bw LpDaAaS8q5VM7dCmhtu8jzYOFyDvAZrmT5s1fLHu/FegEgMQAvHVR+ePLhebGRwl IqAdmnmTV8kwVXz7RdhrxF61/0SgVqNqf4+IUszFInpHErdCIZZYRc7kw9GNtdYK AQKB8Qw3/9gWIc9vsd1ZxLjQ1RJxDEMBvAVUM9Jc40m6ML4lRpmDGRDnIAlha2Uc FkEVn2RQ6l+w58s4bhb6h8NBXVkLTg== =9hH2 -----END PGP SIGNATURE----- --Sig_/j/.C7KS_WRAAcH/i3tvI2vT--