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=-5.3 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,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 420AEC433E0 for ; Mon, 27 Jul 2020 17:31:03 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 276082073E for ; Mon, 27 Jul 2020 17:31:03 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=armlinux.org.uk header.i=@armlinux.org.uk header.b="gNMTf3a9" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730835AbgG0RbC (ORCPT ); Mon, 27 Jul 2020 13:31:02 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:38516 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1730662AbgG0RbC (ORCPT ); Mon, 27 Jul 2020 13:31:02 -0400 Received: from pandora.armlinux.org.uk (pandora.armlinux.org.uk [IPv6:2001:4d48:ad52:32c8:5054:ff:fe00:142]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 028CEC061794; Mon, 27 Jul 2020 10:31:02 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=armlinux.org.uk; s=pandora-2019; h=Sender:In-Reply-To:Content-Type: MIME-Version:References:Message-ID:Subject:Cc:To:From:Date:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Id: List-Help:List-Unsubscribe:List-Subscribe:List-Post:List-Owner:List-Archive; bh=OWoBvMBmWyDilWMUdxwiwp8BDkF9aBjJr3HcaF0ozXo=; b=gNMTf3a99kpRORweCKLBEzsKU iSe3KroPt7Iqtw/bTqtUJLI9vbLgXjhJlmVBffJQNmOwMpMP444Elz5KmXqbFFYSaohyNGYv4trFv kLXIAej49+UmDQL8ZkxwyYIytiTS6jYsMNbGzKLZXhqjRnzYO+298DuWWtJJ/3F7w24d2Or+d16Gv Mr4LBEDVQeIAInXJvWmh7F6sxHglSw/9CUoqxs2GKOo3YdDcpdYsJ5AktzS+SGXMUVkN6hIl8BwvK RznIj6+WwBcv3VOUHARDlkq5x9OqDNV5L3g0xmJh7xkl0hjixEhim6FZVOCJy3WEb3hRWOBKjsynO HR4yAjzmQ==; Received: from shell.armlinux.org.uk ([fd8f:7570:feb6:1:5054:ff:fe00:4ec]:44886) by pandora.armlinux.org.uk with esmtpsa (TLS1.3:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.92) (envelope-from ) id 1k06xh-00037t-BM; Mon, 27 Jul 2020 18:30:53 +0100 Received: from linux by shell.armlinux.org.uk with local (Exim 4.92) (envelope-from ) id 1k06xf-0003pn-Gq; Mon, 27 Jul 2020 18:30:51 +0100 Date: Mon, 27 Jul 2020 18:30:51 +0100 From: Russell King - ARM Linux admin To: Alexandre Belloni Cc: Jon Nettleton , Rob Herring , Miguel Borges de Freitas , a.zummo@towertech.it, Baruch Siach , Shawn Guo , Sascha Hauer , Sascha Hauer , Fabio Estevam , NXP Linux Team , devicetree , linux-arm-kernel , Linux Kernel Mailing List Subject: Re: [PATCH v2 1/3] dt-bindings: rtc: pcf8523: add DSM pm option for battery switch-over Message-ID: <20200727173051.GM1551@shell.armlinux.org.uk> References: <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> <20200727154104.GE239143@piout.net> <20200727154335.GL1551@shell.armlinux.org.uk> <20200727161632.GF239143@piout.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200727161632.GF239143@piout.net> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: devicetree-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: devicetree@vger.kernel.org On Mon, Jul 27, 2020 at 06:16:32PM +0200, Alexandre Belloni wrote: > On 27/07/2020 17:55:50+0200, Jon Nettleton wrote: > > > So, can we please have that discussion, it is pertinent to this patch. > > > > > > > Thinking about this some more, I believe whether or not an IOCTL > > interface is in the works or needed is irrelevant. This patch > > describes the hardware and how it is designed and the topic of > > discussion is if we need a simple boolean state, or if we need > > something that could be used to support dynamic configuration in the > > future. I would rather make this decision now rather than keep > > tacking on boolean config options, or revisit a bunch of device-tree > > changes. > > Something that would describe the hardware is a property telling whether > the filter is present on VDD, not a property selecting DSM. The driver > can then chose to avoid standard mode when needed. Whether DSM needs to be enabled or not is _not_ just a function of whether there is a filter present or not. The requirement in the data sheet is that when the VDD supply drops below 2.5V, it does not fall more than 0.7V/ms. That can be achieved many different ways, not only by adding a resistive filter to the VDD supply to the RTC. It could also be achieved via the design of the power supply - for example, having a large enough reservoir capacitor to ensure under all loads that the VDD supply will not fall faster than 0.7V/ms. There are many ways to meet this requirement. Adding a DT property to indicate whether the filter is present or not is definitely not the right approach. Should we also add properties for every possible solution to this problem. vdd-has-filter; psu-has-large-capacitors; ... etc ... -- RMK's Patch system: https://www.armlinux.org.uk/developer/patches/ FTTP is here! 40Mbps down 10Mbps up. Decent connectivity at last!