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=-0.8 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,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 43EBFC433DF for ; Mon, 8 Jun 2020 18:20:26 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 1A9E7206D5 for ; Mon, 8 Jun 2020 18:20:26 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=linaro.org header.i=@linaro.org header.b="FvaaSm5t" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726027AbgFHSUZ (ORCPT ); Mon, 8 Jun 2020 14:20:25 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:49780 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725927AbgFHSUX (ORCPT ); Mon, 8 Jun 2020 14:20:23 -0400 Received: from mail-wr1-x442.google.com (mail-wr1-x442.google.com [IPv6:2a00:1450:4864:20::442]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 6BBC3C08C5C5 for ; Mon, 8 Jun 2020 11:20:22 -0700 (PDT) Received: by mail-wr1-x442.google.com with SMTP id r7so18494613wro.1 for ; Mon, 08 Jun 2020 11:20:22 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linaro.org; s=google; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:content-transfer-encoding:in-reply-to; bh=2CJM5g0VuqYFNIM+dUzodFUTj18WAdux3/u8z24zvRA=; b=FvaaSm5tyr6RBgjbPNfvrJLlZcAn3DmzQGeyoQrQ5NJotNGMRI+S/WTL4cZGcvbeKQ OeiYno6xBUEcQi5WgLfPg1nv7oOkxmoaBpZ6QtIPDVlQPQdk8Xg1KETQTvd/QbsmmRZg rKCAizdiGMf2yjrMRJkrYUJTQ8RhPDKv4CF4YBH4XvdeaNYdcf0hTu/38GolQI/FykDN 4Wtn17IHKjfImnRlO7XuYIJCSylUrNpYSAcVJ0FF2ljUmpkm69oK59PmBzzl1uzp468r sdFV0WqzFhOkNZXY3HflI0dAEsSOqMmu2UtExqdHiQfNrXygDGlFgbgtHXGR4oIhwsQF uzWw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:content-transfer-encoding :in-reply-to; bh=2CJM5g0VuqYFNIM+dUzodFUTj18WAdux3/u8z24zvRA=; b=bW6xiI9HOUPKDBRniGVuFosKfpBIcMd/+CqGr+JgVeZQjmAp4MSvaB8rN8nHOhkyuH wvFQPzM8/yfErO28P6hRTYHRZNd4jongmYx8HxKIvUNdp4x1iw4By69egbVM//bIH/1r znqRiyqJOCQ9DkfTZhnL7viW+mUdhd+EQpgaA0hUOnDu5LIXeFLV5+tfHtjWfM8i9zAd BE/lg1h8bSinYIHAB6zC5khOLX6TfNJZUoN9Dif7FBkl8TqQ9KVLtA4AfZm+AJPmORNG 036iq0LTmur4DMJ/J2iHK4MM3Sh4LEHInzNo518Jv2sxVIM0cSGMdQ/Fav9GCjpLudgt RoEg== X-Gm-Message-State: AOAM532BNEWFGS/1VLn+94HMVtsf2OgEGPsXTrK6Kj3BZMbju3bU8Uu9 TGgvNOsewBPqpN5rLusI2ZP+Jg== X-Google-Smtp-Source: ABdhPJxumzJA4nkmctYgB3lMSJVUnSMTyEhafMZJYxSm51uV/tmOYuDxGF7eIqOVSIVmr0U8Lef0xg== X-Received: by 2002:a05:6000:11cd:: with SMTP id i13mr86707wrx.141.1591640420821; Mon, 08 Jun 2020 11:20:20 -0700 (PDT) Received: from dell ([95.147.198.92]) by smtp.gmail.com with ESMTPSA id a7sm358274wmh.14.2020.06.08.11.20.19 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 08 Jun 2020 11:20:20 -0700 (PDT) Date: Mon, 8 Jun 2020 19:20:18 +0100 From: Lee Jones To: Andy Shevchenko Cc: Ranjani Sridharan , david.m.ertman@intel.com, shiraz.saleem@intel.com, 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 , Uwe =?iso-8859-1?Q?Kleine-K=F6nig?= , Wim Van Sebroeck , Shawn Guo , Li Yang , Thomas Gleixner , Jason Cooper , Marc Zyngier , Greg Kroah-Hartman , Andy Shevchenko Subject: Re: [PATCH v4 02/11] mfd: Add support for Kontron sl28cpld management controller Message-ID: <20200608182018.GB4106@dell> 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> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: Sender: devicetree-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: devicetree@vger.kernel.org On Mon, 08 Jun 2020, Andy Shevchenko wrote: > +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. Exactly. Because of the reasons in the paragraph above: "complex shared and sometimes intertwined batches of register sets to be consumed by multiple (sub-)devices spanning different subsystems" > > 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. > -- Lee Jones [李琼斯] Senior Technical Lead - Developer Services Linaro.org │ Open source software for Arm SoCs Follow Linaro: Facebook | Twitter | Blog