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=-4.0 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS 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 7731AC433DF for ; Mon, 27 Jul 2020 15:41:13 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 5B48A206E7 for ; Mon, 27 Jul 2020 15:41:13 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730884AbgG0PlL (ORCPT ); Mon, 27 Jul 2020 11:41:11 -0400 Received: from relay9-d.mail.gandi.net ([217.70.183.199]:34315 "EHLO relay9-d.mail.gandi.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1730527AbgG0PlI (ORCPT ); Mon, 27 Jul 2020 11:41:08 -0400 X-Originating-IP: 90.66.108.79 Received: from localhost (lfbn-lyo-1-1932-79.w90-66.abo.wanadoo.fr [90.66.108.79]) (Authenticated sender: alexandre.belloni@bootlin.com) by relay9-d.mail.gandi.net (Postfix) with ESMTPSA id CA78DFF81B; Mon, 27 Jul 2020 15:41:04 +0000 (UTC) Date: Mon, 27 Jul 2020 17:41:04 +0200 From: Alexandre Belloni To: Russell King - ARM Linux admin Cc: Rob Herring , miguelborgesdefreitas@gmail.com, a.zummo@towertech.it, baruch@tkos.co.il, shawnguo@kernel.org, s.hauer@pengutronix.de, kernel@pengutronix.de, festevam@gmail.com, linux-imx@nxp.com, devicetree@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v2 1/3] dt-bindings: rtc: pcf8523: add DSM pm option for battery switch-over Message-ID: <20200727154104.GE239143@piout.net> References: <20200719145028.3370-3-miguelborgesdefreitas@gmail.com> <20200720112401.4620-1-miguelborgesdefreitas@gmail.com> <20200720112401.4620-2-miguelborgesdefreitas@gmail.com> <20200723174905.GA596242@bogus> <20200723195755.GV3428@piout.net> <20200727094553.GH1551@shell.armlinux.org.uk> <20200727144938.GC239143@piout.net> <20200727152439.GK1551@shell.armlinux.org.uk> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200727152439.GK1551@shell.armlinux.org.uk> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 27/07/2020 16:24:39+0100, Russell King - ARM Linux admin wrote: > On Mon, Jul 27, 2020 at 04:49:38PM +0200, Alexandre Belloni wrote: > > On 27/07/2020 10:45:53+0100, Russell King - ARM Linux admin wrote: > > > > This is but this shouldn't be a DT property as it has to be changed > > > > dynamically. I'm working on an ioctl interface to change this > > > > configuration. > > > > > > Why does it need to be changed dynamically? If the hardware components > > > are not fitted to allow the RTC to be safely used without DSM, then > > > why should userspace be able to disable DSM? > > > > For RTCs with a standby mode, you want to be able to return to standby > > mode. > > > > That would happen for example after factory flashing in that common use > > case: > > - the board is manufactured > > - Vbackup is installed, the RTC switches to standby mode > > - the board is then booted to flash a system, Vprimary is now present, > > the RTC switches to DSM. > > > > At this point, if the board is simply shut down, the RTC will start > > draining Vbackup before leaving the factory. Instead, we want to be able > > to return to standby mode until the final user switches the product on > > for the first time. > > I don't think you're understanding what's going on with this proposed > patch. The cubox-i does work today, and the RTC does survive most > power-downs. There are situations where it doesn't. > > So, let's take your process above. > > - the board is manufactured > - Vbackup is installed, the RTC switches to standby mode > - the board is then booted to flash a system, Vprimary is now present > - the board is powered down. the RTC _might_ switch over to battery > if it notices the power failure in time, or it might not. A random > sample of units leaving the factory have the RTC in standby mode. > Others are draining the battery. > > I'm not saying what you propose isn't a good idea. I'm questioning > why we should expose this in the generic kernel on platforms where > it's likely to end up with the RTC being corrupted. > Note that I didn't say we should expose settings that are not working but it is a different discussion. I was explaining why we need to be able to change it dynamically. > Now, I question your idea that units should leave the factory without > the RTC being programmed. We know that lovely systemd goes utterly > bonkers if the system time is beyond INT_MAX. If the RTC leaves > standby mode containing a date which we translate beyond INT_MAX, > systemd will refuse to boot the system, and the user will have no > way to set the correct time. The user returns the device to the > supplier as faulty... This is doesn't happen since v4.17. -- Alexandre Belloni, Bootlin Embedded Linux and Kernel engineering https://bootlin.com 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=-4.0 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS 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 45D80C433E4 for ; Mon, 27 Jul 2020 15:42:57 +0000 (UTC) Received: from merlin.infradead.org (merlin.infradead.org [205.233.59.134]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 1421F20729 for ; Mon, 27 Jul 2020 15:42:56 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="eXerD3MA" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 1421F20729 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=bootlin.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=merlin.20170209; h=Sender:Content-Transfer-Encoding: Content-Type:Cc:List-Subscribe:List-Help:List-Post:List-Archive: List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:References:Message-ID: Subject:To:From:Date:Reply-To:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=iRoW8e2bmbyLMMSmMat9e4T9Ut/AIA5dfU7205rW1I4=; b=eXerD3MAYSn22QZ/BOC9Th9oT oq7+dsiPPeCgFB3ZYfOGbqNRxf5lXbjPyTVq4DAWFt223uea7FHovuK0PsXcKqg4x19Qj1JmQqVuF JhVAep/LHNwSMOunxPgwrIMSizoh+jGvGCgxAw5s2RPNoRq+xkkcifmXXu7p8FYgFSexz+MkZca7E J7jeerIhG4chcm2te4Pron9r43FCI70jha5WbF7yvVAZuLwnE5BVk6BRxuYQz/GtGdqDHcOGOpK4l Pomn77ieHmjjV7P/dBXBu68G9Jf4d5N1+Dnm67djyXKsgLXTYMweHWJbeGxInxN1WFGbao0Z7TdGz Q7ylmb+PA==; Received: from localhost ([::1] helo=merlin.infradead.org) by merlin.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1k05FX-00005O-Os; Mon, 27 Jul 2020 15:41:11 +0000 Received: from relay9-d.mail.gandi.net ([217.70.183.199]) by merlin.infradead.org with esmtps (Exim 4.92.3 #3 (Red Hat Linux)) id 1k05FV-0008WD-Jm for linux-arm-kernel@lists.infradead.org; Mon, 27 Jul 2020 15:41:10 +0000 X-Originating-IP: 90.66.108.79 Received: from localhost (lfbn-lyo-1-1932-79.w90-66.abo.wanadoo.fr [90.66.108.79]) (Authenticated sender: alexandre.belloni@bootlin.com) by relay9-d.mail.gandi.net (Postfix) with ESMTPSA id CA78DFF81B; Mon, 27 Jul 2020 15:41:04 +0000 (UTC) Date: Mon, 27 Jul 2020 17:41:04 +0200 From: Alexandre Belloni To: Russell King - ARM Linux admin Subject: Re: [PATCH v2 1/3] dt-bindings: rtc: pcf8523: add DSM pm option for battery switch-over Message-ID: <20200727154104.GE239143@piout.net> References: <20200719145028.3370-3-miguelborgesdefreitas@gmail.com> <20200720112401.4620-1-miguelborgesdefreitas@gmail.com> <20200720112401.4620-2-miguelborgesdefreitas@gmail.com> <20200723174905.GA596242@bogus> <20200723195755.GV3428@piout.net> <20200727094553.GH1551@shell.armlinux.org.uk> <20200727144938.GC239143@piout.net> <20200727152439.GK1551@shell.armlinux.org.uk> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20200727152439.GK1551@shell.armlinux.org.uk> X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20200727_114109_837720_C1F2687B X-CRM114-Status: GOOD ( 32.46 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Rob Herring , baruch@tkos.co.il, kernel@pengutronix.de, a.zummo@towertech.it, festevam@gmail.com, s.hauer@pengutronix.de, linux-kernel@vger.kernel.org, devicetree@vger.kernel.org, linux-imx@nxp.com, miguelborgesdefreitas@gmail.com, shawnguo@kernel.org, linux-arm-kernel@lists.infradead.org Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On 27/07/2020 16:24:39+0100, Russell King - ARM Linux admin wrote: > On Mon, Jul 27, 2020 at 04:49:38PM +0200, Alexandre Belloni wrote: > > On 27/07/2020 10:45:53+0100, Russell King - ARM Linux admin wrote: > > > > This is but this shouldn't be a DT property as it has to be changed > > > > dynamically. I'm working on an ioctl interface to change this > > > > configuration. > > > > > > Why does it need to be changed dynamically? If the hardware components > > > are not fitted to allow the RTC to be safely used without DSM, then > > > why should userspace be able to disable DSM? > > > > For RTCs with a standby mode, you want to be able to return to standby > > mode. > > > > That would happen for example after factory flashing in that common use > > case: > > - the board is manufactured > > - Vbackup is installed, the RTC switches to standby mode > > - the board is then booted to flash a system, Vprimary is now present, > > the RTC switches to DSM. > > > > At this point, if the board is simply shut down, the RTC will start > > draining Vbackup before leaving the factory. Instead, we want to be able > > to return to standby mode until the final user switches the product on > > for the first time. > > I don't think you're understanding what's going on with this proposed > patch. The cubox-i does work today, and the RTC does survive most > power-downs. There are situations where it doesn't. > > So, let's take your process above. > > - the board is manufactured > - Vbackup is installed, the RTC switches to standby mode > - the board is then booted to flash a system, Vprimary is now present > - the board is powered down. the RTC _might_ switch over to battery > if it notices the power failure in time, or it might not. A random > sample of units leaving the factory have the RTC in standby mode. > Others are draining the battery. > > I'm not saying what you propose isn't a good idea. I'm questioning > why we should expose this in the generic kernel on platforms where > it's likely to end up with the RTC being corrupted. > Note that I didn't say we should expose settings that are not working but it is a different discussion. I was explaining why we need to be able to change it dynamically. > Now, I question your idea that units should leave the factory without > the RTC being programmed. We know that lovely systemd goes utterly > bonkers if the system time is beyond INT_MAX. If the RTC leaves > standby mode containing a date which we translate beyond INT_MAX, > systemd will refuse to boot the system, and the user will have no > way to set the correct time. The user returns the device to the > supplier as faulty... This is doesn't happen since v4.17. -- Alexandre Belloni, Bootlin Embedded Linux and Kernel engineering https://bootlin.com _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel