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=-21.4 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,MENTIONS_GIT_HOSTING,SPF_HELO_NONE,SPF_PASS autolearn=unavailable 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 3B446C433EF for ; Fri, 3 Sep 2021 00:53:57 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 20F186108B for ; Fri, 3 Sep 2021 00:53:57 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231670AbhICAyz (ORCPT ); Thu, 2 Sep 2021 20:54:55 -0400 Received: from mail.kernel.org ([198.145.29.99]:55164 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231161AbhICAyy (ORCPT ); Thu, 2 Sep 2021 20:54:54 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id 5A7FB610A1; Fri, 3 Sep 2021 00:53:55 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1630630435; bh=ESjKUQjilvoa8yjcHYk5EoAu/HqzJrgOoao4t51tuiw=; h=References:In-Reply-To:From:Date:Subject:To:Cc:From; b=nsSWW2fkARm1CWQfjsfE++kELQD2ttwaVF9egcUeuuj9jVYLq36tV0rz6t8wFYtRP 2juWr+f/e1Ssr1R2giu7AnqFFxuQjkLVhSKy+2CcrNpSRx9iHohbtsILxhfWGYmBWx GcIvIJ4ww3t1ViFiHKBoRuJtyvt3v6UhiwYkWLByCDo/Rk5kmge/zDa7fOPn6fYso7 JoHLMD9B21ruCSO3aXpFVPWY2FNJS8EFTVtsxob8nAnMV9lUzH4N7UcO4Nl8dfdRqI AyST0OPRZhX4XtC/jazwJi/QciXL4oWdNdxyvRmi7x8Qi+RIPIj23xPXbfyoYOT+wL NriLUtk351bVw== Received: by mail-ej1-f53.google.com with SMTP id x11so8592405ejv.0; Thu, 02 Sep 2021 17:53:55 -0700 (PDT) X-Gm-Message-State: AOAM531nvtHlTY+4UNopt7eUytx3Z10UnhkNpj0nirBY4LjZIlRuJOD4 EZ8LGNrFC2Dr13vCQ3YAuwgMsa2Ke9L/imruMw== X-Google-Smtp-Source: ABdhPJzgXCEgW8AMIrdDuiVErt8Lcc+lHdjEl4dO9chPIYkQnJOqKI0bLvrmBj8SJrt1vZKVVzTI79Sk1om36yhSsd4= X-Received: by 2002:a17:906:8cd:: with SMTP id o13mr1086206eje.341.1630630433827; Thu, 02 Sep 2021 17:53:53 -0700 (PDT) MIME-Version: 1.0 References: <20210902025528.1017391-1-saravanak@google.com> <20210902025528.1017391-3-saravanak@google.com> In-Reply-To: From: Rob Herring Date: Thu, 2 Sep 2021 19:53:42 -0500 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [PATCH v1 2/2] of: platform: Mark bus devices nodes with FWNODE_FLAG_NEVER_PROBES To: Saravana Kannan Cc: Greg Kroah-Hartman , "Rafael J. Wysocki" , Frank Rowand , Len Brown , Ulf Hansson , Android Kernel Team , "linux-kernel@vger.kernel.org" , devicetree@vger.kernel.org, "open list:ACPI FOR ARM64 (ACPI/arm64)" Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-acpi@vger.kernel.org On Thu, Sep 2, 2021 at 2:29 PM Saravana Kannan wrote: > > On Thu, Sep 2, 2021 at 12:03 PM Rob Herring wrote: > > > > On Thu, Sep 2, 2021 at 11:57 AM Saravana Kannan wrote: > > > > > > On Thu, Sep 2, 2021 at 7:24 AM Rob Herring wrote: > > > > > > > > On Wed, Sep 1, 2021 at 9:55 PM Saravana Kannan wrote: > > > > > > > > > > We don't want fw_devlink creating device links for bus devices as > > > > > they'll never probe. So mark those device node with this flag. > > > > > > > > > > Signed-off-by: Saravana Kannan > > > > > --- > > > > > drivers/of/platform.c | 16 ++++++++++++++++ > > > > > 1 file changed, 16 insertions(+) > > > > > > > > > > diff --git a/drivers/of/platform.c b/drivers/of/platform.c > > > > > index 74afbb7a4f5e..42b3936d204a 100644 > > > > > --- a/drivers/of/platform.c > > > > > +++ b/drivers/of/platform.c > > > > > @@ -392,6 +392,22 @@ static int of_platform_bus_create(struct device_node *bus, > > > > > if (!dev || !of_match_node(matches, bus)) > > > > > return 0; > > > > > > > > > > + /* > > > > > + * If the bus node has only one compatible string value and it has > > > > > + * matched as a bus node, it's never going to get probed by a device > > > > > + * driver. So flag it as such so that fw_devlink knows not to create > > > > > + * device links with this device. > > > > > + * > > > > > + * This doesn't catch all devices that'll never probe, but this is good > > > > > + * enough for now. > > > > > + * > > > > > + * This doesn't really work for PPC because of how it uses > > > > > + * of_platform_bus_probe() to add normal devices. So ignore PPC cases. > > > > > + */ > > > > > + if (!IS_ENABLED(CONFIG_PPC) && > > > > > + of_property_count_strings(bus, "compatible") == 1) > > > > > + bus->fwnode.flags |= FWNODE_FLAG_NOT_DEVICE; > > > > > > > > This looks fragile relying on 1 compatible string, and the DT flags in > > > > this code have been fragile too. I'm pretty sure we have cases of > > > > simple-bus or simple-mfd that also have another compatible. > > > > > > > > Couldn't we solve this with a simple driver? > > > > > > Oh, I didn't think you'd like that. I'd lean towards that option too > > > if we can address some of the other concerns below. > > > > > > > Make 'simple-pm-bus' > > > > driver work for other cases? > > > > > > > BTW, this patch doesn't even work for > > > > simple-pm-bus. > > > > > > How do you mean? Because simple-pm-bus already has a driver and > > > doesn't set "matches" param when it calls of_platform_populate() and > > > this flag won't be set. So at least for simple-pm-bus I don't see any > > > issue. > > > > You're right. > > > > > I was trying to reuse of_default_bus_match_table without explicitly > > > referring to it, but if it's confusing I can add a separate list of > > > compatible strings and use those here instead of using "matches". > > > > What happens with a non-default table? I'm not sure we can assume the > > same behavior. > > > > > > A driver for simple-bus may cause issues if there's a > > > > more specific driver to bind to as we don't handle that. It's simply > > > > whichever matches first. > > > > > > Right, this is my worry. Especially for devices like this (there are > > > plenty of cases like this) which have a driver that probes them but > > > also lists simple-bus > > > https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/arch/arm/boot/dts/arm-realview-pb11mp.dts?id=73f3af7b4611d77bdaea303fb639333eb28e37d7#n299 > > > > Uhh, that one is certainly a leakage of wanting an soc_device in the > > hierarchy, not any real bus structure reflecting the h/w. I'm not a > > fan of the soc_device stuff and its optional nature. Everything is an > > SoC, so it should always be there? Or your device hierarchy should > > change when you decide to add a soc_device? > > > > > So as long as there's a compatible string that's not one of the > > > "transparent" busses, this driver shouldn't match. So, I don't think I > > > can get away from checking the compatible strings. > > > > > > How about I check here to make sure all the "compatible" strings are > > > from an approved transparent bus list, and if it's true, I use > > > driver_override to force match it to a transparent bus driver? Would > > > you be okay with that? > > > > Can't we do that within a driver? We check this and fail probe if > > there's a more specific compatible. Then another driver can match and > > probe. > > I was thinking that initially, but if we fail a probe, the driver core > will permanently give up (won't search further) or might end up > retrying with the same driver and never get to the other driver. I'll > send out a v2 with what I described above. It's not too bad and it > will also allow us to handle the PPC cases (we'll just need to keep > adding the simple-bus equivalent entries to a table). I wasn't sure, but I traced the calls and it looks like based on __driver_attach() that if a driver fails probe another one matching should get to probe: /* * Ignore errors returned by ->probe so that the next driver can try * its luck. */ The PPC case is about descending nodes without a compatible string. Rob