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=-0.6 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, 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 67892C433E1 for ; Mon, 8 Jun 2020 10:02:40 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 381C2206A4 for ; Mon, 8 Jun 2020 10:02:40 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="up0PRyxO" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729330AbgFHKCf (ORCPT ); Mon, 8 Jun 2020 06:02:35 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:57560 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729240AbgFHKCe (ORCPT ); Mon, 8 Jun 2020 06:02:34 -0400 Received: from mail-pg1-x542.google.com (mail-pg1-x542.google.com [IPv6:2607:f8b0:4864:20::542]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id EF17DC08C5C3; Mon, 8 Jun 2020 03:02:33 -0700 (PDT) Received: by mail-pg1-x542.google.com with SMTP id s10so8571438pgm.0; Mon, 08 Jun 2020 03:02:33 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=2zoo0ERaliX/JjKEGnYqTQZHfKutQDjXGBUR6MxE50E=; b=up0PRyxOK9NsFIv2bsBl0byvSjs9TKlq7122/ilkRkEttg+3QL6Te0gWz3TYNBv0vi IE21MrMkSmBoOM0mY4Ym6dD4h0fHd8PJqbmjpqRLAoD8EgiLZJlztmdayzlMxvl64uad DTmDDiOoifJ+qZNcLaLd2QSV/HmYZnGjko8DYlFAtHLeNrU6eLEN23fhJDEXcZO9k6su 5btG1FU90NfVPGLZPU9H4xy++nNO22Mb48r9L7eryuGK6DS+fMUjxg5jPDGiU2+oNHCp xKXJVPkjQbjd51oijoYnbZKVI1lUIdfoc2nsSSfQ/4wyGgwYugHqOswiCBWgOn9shtpA CEbg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=2zoo0ERaliX/JjKEGnYqTQZHfKutQDjXGBUR6MxE50E=; b=g+UrNPb+COB2G9HXzGNpVv8bK2+XNK7NVTe7ZrgsXB0MpkLh5baLopiGaSe05kLUc5 2oImWxAnKyh6dMEHOELibjZk6aDSEiBXCnN0ldjjmcZYoBnERto5hInNOpH24o0rwiX7 IdjzgubCAKzsLFb5JP4eTMpwAs+iNdVOZAixwelfZmbWXBzBJn0YlN/aPvbQCv0tXYLT 1zS2tEqhDOl4BgniqlnEbxDY13piiSSf8QO2jWWDdEYmuQBHv3Czyhw16QHGV06i5UOg es1YTLlthzxaR2yJj3B3LiiUzbKmxUeSpWHk5Z83c6B2yY7urQj1y+vwZfApL+su+F4U ez8g== X-Gm-Message-State: AOAM530UZqQ/k2LOEI+e4z8ksSnyG7jN5oQUlqwM2BxhETuCr4ymCLnY HAOIxbzfL7A+fyLCchobg5qZgG7oeQrj9RbKgVI= X-Google-Smtp-Source: ABdhPJx86tPKDhVhcYy12URCDzcRNhNuX2MCH50rKMBNeLvTYoOCyhjdRnZsCXkMUtFO7r9gOz6BiOXhGjPZOdlfhLw= X-Received: by 2002:a63:ff52:: with SMTP id s18mr20149238pgk.203.1591610553061; Mon, 08 Jun 2020 03:02:33 -0700 (PDT) MIME-Version: 1.0 References: <20200604211039.12689-1-michael@walle.cc> <20200604211039.12689-3-michael@walle.cc> <20200605065709.GD3714@dell> <20200605105026.GC5413@sirena.org.uk> <20200606114645.GB2055@sirena.org.uk> <20200608082827.GB3567@dell> In-Reply-To: <20200608082827.GB3567@dell> From: Andy Shevchenko Date: Mon, 8 Jun 2020 13:02:21 +0300 Message-ID: Subject: Re: [PATCH v4 02/11] mfd: Add support for Kontron sl28cpld management controller To: Lee Jones , Ranjani Sridharan , david.m.ertman@intel.com, shiraz.saleem@intel.com Cc: Michael Walle , Rob Herring , Mark Brown , "open list:GPIO SUBSYSTEM" , devicetree , Linux Kernel Mailing List , linux-hwmon@vger.kernel.org, linux-pwm@vger.kernel.org, linux-watchdog@vger.kernel.org, linux-arm Mailing List , Linus Walleij , Bartosz Golaszewski , Jean Delvare , Guenter Roeck , Thierry Reding , =?UTF-8?Q?Uwe_Kleine=2DK=C3=B6nig?= , Wim Van Sebroeck , Shawn Guo , Li Yang , Thomas Gleixner , Jason Cooper , Marc Zyngier , Greg Kroah-Hartman , Andy Shevchenko Content-Type: text/plain; charset="UTF-8" Sender: devicetree-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: devicetree@vger.kernel.org +Cc: some Intel people WRT our internal discussion about similar problem and solutions. On Mon, Jun 8, 2020 at 11:30 AM Lee Jones wrote: > On Sat, 06 Jun 2020, Michael Walle wrote: > > Am 2020-06-06 13:46, schrieb Mark Brown: > > > On Fri, Jun 05, 2020 at 10:07:36PM +0200, Michael Walle wrote: > > > > Am 2020-06-05 12:50, schrieb Mark Brown: ... > Right. I'm suggesting a means to extrapolate complex shared and > sometimes intertwined batches of register sets to be consumed by > multiple (sub-)devices spanning different subsystems. > > Actually scrap that. The most common case I see is a single Regmap > covering all child-devices. Yes, because often we need a synchronization across the entire address space of the (parent) device in question. > It would be great if there was a way in > which we could make an assumption that the entire register address > space for a 'tagged' (MFD) device is to be shared (via Regmap) between > each of the devices described by its child-nodes. Probably by picking > up on the 'simple-mfd' compatible string in the first instance. > > Rob, is the above something you would contemplate? > > Michael, do your register addresses overlap i.e. are they intermingled > with one another? Do multiple child devices need access to the same > registers i.e. are they shared? > > > > > But, there is more in my driver: > > > > (1) there is a version check > > If we can rid the Regmap dependency, then creating an entire driver to > conduct a version check is unjustifiable. This could become an inline > function which is called by each of the sub-devices instead, for > example. > > > > > (2) there is another function for which there is no suitable linux > > > > subsystem I'm aware of and thus which I'd like to us sysfs > > > > attributes for: This controller supports 16 non-volatile > > > > configuration bits. (this is still TBD) > > There is a place for everything in Linux. > > What do these bits configure? > > > > TBH I'd also say that the enumeration of the subdevices for this > > > device should be in the device rather than the DT, they don't > > > seem to be things that exist outside of this one device. > > > > We're going circles here, formerly they were enumerated in the MFD. > > Yes, they are devices which aren't likely be used outside a > > "sl28cpld", but there might there might be other versions of the > > sl28cpld with other components on different base addresses. I > > don't care if they are enumerated in DT or MFD, actually, I'd > > prefer the latter. _But_ I would like to have the device tree > > properties for its subdevices, e.g. the ones for the watchdog or > > whatever components there might be in the future. > > [...] > > > MFD core can > > match a device tree node today; but only one per unique compatible > > string. So what should I use to differentiate the different > > subdevices? > > Right. I have been aware of this issue. The only suitable solution > to this would be to match on 'reg'. > > FYI: I plan to fix this. > > If your register map needs to change, then I suggest that this is > either a new device or at least a different version of the device and > would also have to be represented as different (sub-)mfd_cell. > > > Rob suggested the internal offset, which I did here. > > FWIW, I don't like this idea. DTs should not have to be modified > (either in the first instance or subsequently) or specifically > designed to patch inadequacies in any given OS. > > > But then, there is less use in duplicating the offsets in the MFD > > just to have the MFD enumerate the subdevices and then match > > the device tree nodes against it. I can just use > > of_platform_populate() to enumerate the children and I won't > > have to duplicate the base addresses. > > Which is fine. However this causes a different issue for you. By > stripping out the MFD code you render the MFD portion seemingly > superfluous. Another issue driver authors commonly contend with. -- With Best Regards, Andy Shevchenko