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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 9451CC433EF for ; Tue, 26 Apr 2022 21:38:45 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1355443AbiDZVlw (ORCPT ); Tue, 26 Apr 2022 17:41:52 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:43626 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1346480AbiDZVlt (ORCPT ); Tue, 26 Apr 2022 17:41:49 -0400 Received: from mail-oa1-f44.google.com (mail-oa1-f44.google.com [209.85.160.44]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id A260A63BC4 for ; Tue, 26 Apr 2022 14:38:40 -0700 (PDT) Received: by mail-oa1-f44.google.com with SMTP id 586e51a60fabf-e2fa360f6dso51758fac.2 for ; Tue, 26 Apr 2022 14:38:40 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to; bh=zhyNtTRWKpgiVoHNVp/CiGMxHi3Y9XR1OWQf9/EqURQ=; b=hK1b9xtu92GWprnrtxyib1Rj14X4Y59I6aKnKTTaw1Sq9N3sys0bT3Pctry/qEIbmb dfo+8m7rbu4TEHEcQRecbjbCZjDcQiF56VRG4EADieoRuzdZq3ZluxK3c0eQLhwE9OeO J8NE3yalyEbNJoB2xU6wBpMajKZOkYr/h8oZD7xg5oNYo6rcALxkB7qNhgrEqmfJpLJU Lp/0rfUd24OkpW9FaB734o33seTihve4ULWzB6FbIakplDpPdmP92wnEbLjHx5Igu6W7 DyeFjnMO4F4LHgI/bv7Nb+61WbAKeK8Jch3uL0AhYNy8xOrGenvc6UoJTrbPbMlvPUDL jyeQ== X-Gm-Message-State: AOAM531yTTuagzZVsFpLtOkXCtFaa6KGDggWDoWSrjbmfSe1UZKqv6BC owjZe+rllOPZ7y6joPXz1w== X-Google-Smtp-Source: ABdhPJydqYRqWI0cp4kXY25TEM4qbC2jQJOu+ISl9HwJMZmr7tsR1Tjj0vCRAPwtiK15Bcd2ft593Q== X-Received: by 2002:a05:6870:d210:b0:e2:c10b:a7b with SMTP id g16-20020a056870d21000b000e2c10b0a7bmr10187521oac.181.1651009119901; Tue, 26 Apr 2022 14:38:39 -0700 (PDT) Received: from robh.at.kernel.org (66-90-144-107.dyn.grandenetworks.net. [66.90.144.107]) by smtp.gmail.com with ESMTPSA id y22-20020a056870389600b000e93d386d97sm1252404oan.31.2022.04.26.14.38.39 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 26 Apr 2022 14:38:39 -0700 (PDT) Received: (nullmailer pid 2577401 invoked by uid 1000); Tue, 26 Apr 2022 21:38:38 -0000 Date: Tue, 26 Apr 2022 16:38:38 -0500 From: Rob Herring To: Arnd Bergmann Cc: Linus Walleij , "Hawkins, Nick" , "Verdun, Jean-Marie" , Joel Stanley , OpenBMC Maillist , Daniel Lezcano , Thomas Gleixner , Linux Kernel Mailing List Subject: Re: [PATCH v5 04/11] clocksource/drivers: Add HPE GXP timer Message-ID: References: <20220421192132.109954-1-nick.hawkins@hpe.com> <20220421192132.109954-5-nick.hawkins@hpe.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Apr 26, 2022 at 08:00:20AM +0200, Arnd Bergmann wrote: > On Mon, Apr 25, 2022 at 10:38 PM Linus Walleij wrote: > > On Fri, Apr 22, 2022 at 3:16 PM Arnd Bergmann wrote: > > > On Thu, Apr 21, 2022 at 9:21 PM wrote: > > > > > > > + > > > > +static struct platform_device gxp_watchdog_device = { > > > > + .name = "gxp-wdt", > > > > + .id = -1, > > > > +}; > > > > +/* > > > > + * This probe gets called after the timer is already up and running. This will create > > > > + * the watchdog device as a child since the registers are shared. > > > > + */ > > > > + > > > > +static int gxp_timer_probe(struct platform_device *pdev) > > > > +{ > > > > + struct device *dev = &pdev->dev; > > > > + > > > > + /* Pass the base address (counter) as platform data and nothing else */ > > > > + gxp_watchdog_device.dev.platform_data = local_gxp_timer->counter; > > > > + gxp_watchdog_device.dev.parent = dev; > > > > + return platform_device_register(&gxp_watchdog_device); > > > > +} > > > > > > I don't understand what this is about: the device should be created from > > > DT, not defined statically in the code. There are multiple ways of creating > > > a platform_device from a DT node, or you can allocate one here, but static > > > definitions are generally a mistake. > > > > > > I see that you copied this from the ixp4xx driver, so I think we should fix this > > > there as well. > > > > The ixp4xx driver looks like that because the register range used for > > the timer and the watchdog is combined, i.e. it is a single IP block: > > > > timer@c8005000 { > > compatible = "intel,ixp4xx-timer"; > > reg = <0xc8005000 0x100>; > > interrupts = <5 IRQ_TYPE_LEVEL_HIGH>; > > }; > > > > Device tree probing does not allow two devices to probe from the same > > DT node, so this was solved by letting the (less important) watchdog > > be spawn as a platform device from the timer. > > > > I don't know if double-probing for the same register range can be fixed, > > but I was assuming that the one-compatible-to-one-driver assumption > > was pretty hard-coded into the abstractions. Maybe it isn't? > > Having a child device is fine, my objection was about the way > the device is created from a 'static platform_device ...' definition > rather than having the device structure allocated at probe time. > > > Another way is of course to introduce an MFD. That becomes > > problematic in another way: MFD abstractions are supposed to > > be inbetween the resource and the devices it spawns, and with > > timers/clocksources this creates a horrible special-casing since the > > MFD bus (the parent may be providing e.g. an MMIO regmap) > > then need to be early-populated and searched by the timer core > > from TIMER_OF_DECLARE() early in boot. > > > > So this solution was the lesser evil that I could think about. > > There are multiple ways of doing this that we already discussed > in the thread. The easiest is probably to have a child node without > custom registers in the DT and then use the DT helpers to > populate the linux devices with the correct data. I think that's what the wdt binding is doing, but I don't like that. Maybe it's not a child node, I can't tell. Bindings should not be decided on the *current* driver split on one particular OS. This looks like 1 block, so 1 node. If that doesn't work well or easy for Linux, then we should fix Linux. Rob