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 A6DEEC433E1 for ; Tue, 9 Jun 2020 14:38:37 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 834A1207ED for ; Tue, 9 Jun 2020 14:38:37 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=walle.cc header.i=@walle.cc header.b="cEH2mdWX" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730004AbgFIOih (ORCPT ); Tue, 9 Jun 2020 10:38:37 -0400 Received: from ssl.serverraum.org ([176.9.125.105]:36211 "EHLO ssl.serverraum.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726395AbgFIOig (ORCPT ); Tue, 9 Jun 2020 10:38:36 -0400 Received: from ssl.serverraum.org (web.serverraum.org [172.16.0.2]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ssl.serverraum.org (Postfix) with ESMTPSA id 1B4C422F2D; Tue, 9 Jun 2020 16:38:31 +0200 (CEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=walle.cc; s=mail2016061301; t=1591713512; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=3ZPJRQPjyIuPfU5SHFsD+L8Q03R3+eZsQvqJ5K0dqDQ=; b=cEH2mdWXJgiXk5AYmdHK2ORPPLW0kmX5gHUPbeGjN4COswBGwClKjt2xvIVY37IpTQHWrV 5w99q1qD+cl6dn+sw3zbCeKnqavpkSE/lERuAHNegK905kSkxRCahqrr4BxkdtV93EcvCO sDDLQ2q+b/rGGOqSyyduIDIYa9RDBo8= MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII; format=flowed Content-Transfer-Encoding: 7bit Date: Tue, 09 Jun 2020 16:38:31 +0200 From: Michael Walle To: Lee Jones Cc: Andy Shevchenko , Ranjani Sridharan , david.m.ertman@intel.com, shiraz.saleem@intel.com, 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-K?= =?UTF-8?Q?=C3=B6nig?= , 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 In-Reply-To: <20200609064735.GH4106@dell> References: <20200605065709.GD3714@dell> <20200605105026.GC5413@sirena.org.uk> <20200606114645.GB2055@sirena.org.uk> <20200608082827.GB3567@dell> <7d7feb374cbf5a587dc1ce65fc3ad672@walle.cc> <20200608185651.GD4106@dell> <32231f26f7028d62aeda8fdb3364faf1@walle.cc> <20200609064735.GH4106@dell> User-Agent: Roundcube Webmail/1.4.4 Message-ID: <32287ac0488f7cbd5a7d1259c284e554@walle.cc> X-Sender: michael@walle.cc Sender: devicetree-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: devicetree@vger.kernel.org Am 2020-06-09 08:47, schrieb Lee Jones: > On Mon, 08 Jun 2020, Michael Walle wrote: > >> Am 2020-06-08 20:56, schrieb Lee Jones: >> > On Mon, 08 Jun 2020, Michael Walle wrote: >> > >> > > Am 2020-06-08 12:02, schrieb Andy Shevchenko: >> > > > +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? >> > > >> > > No they don't overlap, expect for maybe the version register, which is >> > > just there once and not per function block. >> > >> > Then what's stopping you having each device Regmap their own space? >> >> Because its just one I2C device, AFAIK thats not possible, right? > > Not sure what (if any) the restrictions are. You can only have one device per I2C address. Therefore, I need one device which is enumerated by the I2C bus, which then enumerates its sub-devices. I thought this was one of the use cases for MFD. (Regardless of how a sub-device access its registers). So even in the "simple-regmap" case this would need to be an i2c device. E.g. &i2cbus { mfd-device@10 { compatible = "simple-regmap", "simple-mfd"; reg = <10>; regmap,reg-bits = <8>; regmap,val-bits = <8>; sub-device@0 { compatible = "vendor,sub-device0"; reg = <0>; }; ... }; Or if you just want the regmap: &soc { regmap: regmap@fff0000 { compatible = "simple-regmap"; reg = <0xfff0000>; regmap,reg-bits = <16>; regmap,val-bits = <32>; }; enet-which-needs-syscon-too@1000000 { vendor,ctrl-regmap = <®map>; }; }; Similar to the current syscon (which is MMIO only..). -michael > > I can't think of any reasons why not, off the top of my head. > > Does Regmap only deal with shared accesses from multiple devices > accessing a single register map, or can it also handle multiple > devices communicating over a single I2C channel? > > One for Mark perhaps. > >> > The issues I wish to resolve using 'simple-mfd' are when sub-devices >> > register maps overlap and intertwine. > > [...] > >> > > > > What do these bits configure? >> > > >> > > - hardware strappings which have to be there before the board powers >> > > up, >> > > like clocking mode for different SerDes settings >> > > - "keep-in-reset" bits for onboard peripherals if you want to save >> > > power >> > > - disable watchdog bits (there is a watchdog which is active right >> > > from >> > > the start and supervises the bootloader start and switches to >> > > failsafe >> > > mode if it wasn't successfully started) >> > > - special boot modes, like eMMC, etc. >> > > >> > > Think of it as a 16bit configuration word. >> > >> > And you wish for users to be able to view these at run-time? >> >> And esp. change them. >> >> > Can they adapt any of them on-the-fly or will the be RO? >> >> They are R/W but only will only affect the board behavior after a >> reset. > > I see. Makes sense. This is board controller territory. Perhaps > suitable for inclusion into drivers/soc or drivers/platform.