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=-28.3 required=3.0 tests=BAYES_00,DKIMWL_WL_MED, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,MENTIONS_GIT_HOSTING, SPF_HELO_NONE,SPF_PASS,USER_IN_DEF_DKIM_WL autolearn=ham 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 7C952C433EF for ; Fri, 3 Sep 2021 17:07:32 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 6476761051 for ; Fri, 3 Sep 2021 17:07:32 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1350051AbhICRIb (ORCPT ); Fri, 3 Sep 2021 13:08:31 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:47180 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229692AbhICRIa (ORCPT ); Fri, 3 Sep 2021 13:08:30 -0400 Received: from mail-yb1-xb2e.google.com (mail-yb1-xb2e.google.com [IPv6:2607:f8b0:4864:20::b2e]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 62FC9C061575 for ; Fri, 3 Sep 2021 10:07:30 -0700 (PDT) Received: by mail-yb1-xb2e.google.com with SMTP id k65so11248573yba.13 for ; Fri, 03 Sep 2021 10:07:30 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20210112; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=OV40EXpTRGlRVM1HoPC5Gu3Cw4EBrvOw2+MtPkVXoMk=; b=kzB7fYGbg7lHk+8igESN9SzbBkbtc9t4KWWVzqK8v1bE6TTVDWG0KGTBwRCYRJKsnk qAQ7THYtMYifo7ZOtcsf3uLKKdFLDPT5+OO++Cdy6XTb4K8XlfPtoo+lMU/25pRAIH6l gQ2FF2iYW9An55R7NxSyWAkViTp86Ab9dEpkDtDIQpE13zaFHp6wBxxmA+2AiX5Aa44P w0qySPUoSpArySH3AfafHGmdNB/nAPyuh1OT/xTivtgq0hrbF1XchauwVCIz96m8W2SE +iR6BpfDTQHhNeC5B6J+HjwkYZAk9HINaiTFR4FH72e5CnZsXwnb+ED8++Y9OmKB4iLB vfGg== 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=OV40EXpTRGlRVM1HoPC5Gu3Cw4EBrvOw2+MtPkVXoMk=; b=AORPaW5OaiVDO5r2I64SMa9MyM2890Mg26eKM1vYHjHyz3CuAmq8N0fsAfFEEvgxN5 5ks/0aD+h/5wpshKu9mQy1s0Vcz9VP4E62mU4z8j0eJ4FDV6eoaoSAQYqDLjkFAfbM6f keQueRs1kiZgmClAO1ptO+nqffnlDdmYpFRczy04nwXQkiWf2c00YIdLRP7ZT429qAJ6 33XW9jIObtnUE6wd0u4u725+hJ0h2HlMWD0h+3slA2rE7SA9+810m9eyd9PWFBq+3MxF 9Puf3iHE8dDJSa9oOQBU1xX47/nNrSgORpd2K8CEmKUH4wLodLTzJlcvCM0L2N4ylwyX 1s8Q== X-Gm-Message-State: AOAM5315K8n3RlPFPcLjg8p0Swt95sMnLOKQDl5UxCDaSI1te1B8qXsm UgVCXv1AUNwgXuRcPQ55gjwbomfHoysQKQZCeUg3Tw== X-Google-Smtp-Source: ABdhPJw7D2SeKKJo7n4PeaYN1YXIepjqdR+w6aTnzKZaocQBhgW+SY0tCRPVRXXQ54cpML9/8SqzosEF3KUNZqtd1CM= X-Received: by 2002:a5b:783:: with SMTP id b3mr103810ybq.328.1630688849334; Fri, 03 Sep 2021 10:07:29 -0700 (PDT) MIME-Version: 1.0 References: <20210902025528.1017391-1-saravanak@google.com> <20210902025528.1017391-3-saravanak@google.com> In-Reply-To: From: Saravana Kannan Date: Fri, 3 Sep 2021 10:06:53 -0700 Message-ID: Subject: Re: [PATCH v1 2/2] of: platform: Mark bus devices nodes with FWNODE_FLAG_NEVER_PROBES To: Rob Herring 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 Fri, Sep 3, 2021 at 7:58 AM Rob Herring wrote: > > On Thu, Sep 2, 2021 at 8:16 PM Saravana Kannan wrote: > > > > On Thu, Sep 2, 2021 at 5:53 PM Rob Herring wrote: > > > > > > 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: > > > > __driver_attach() is called over every device already in a bus. It's > > called only when a new driver is registered. So it makes sense that > > one ignores the error returned from probe(). You don't want to fail > > driver registration because one specific device needs to defer probe. > > The behavior should be the same no matter whether the device or driver > is registered first. > > Deferred probe errors are handled differently AFAICT. > > > > > The comment is actually from __device_attach_driver() > > > > > > > > /* > > > * Ignore errors returned by ->probe so that the next driver can try > > > * its luck. > > > */ > > > > I saw that comment too, but isn't the comment wrong/stale? > > I don't know... > > > > > bus_probe_device() -> device_initial_probe() -> __device_attach(). > > > > In __device_attach() we have: > > ret = bus_for_each_drv(dev->bus, NULL, &data, __device_attach_driver); > > > > If you look at bus_for_each_drv()'s comment: > > * ...... If @fn returns anything but 0, we break out > > * and return it. If @start is not NULL, we use it as the head > > * of the list. > > > > Inside __device_attach_driver() we see: > > /* > > * Ignore errors returned by ->probe so that the next driver can try > > * its luck. > > */ > > ret = driver_probe_device(drv, dev); > > if (ret < 0) > > return ret; > > > > So if probe() returned an error, we'd return it right back out. And > > then bus_for_each_drv() will stop searching for more drivers that > > match. > > With the exception of deferred probe, probe errors are made positive > and then ignored. Oh I totally missed this! > > > So I don't think one driver can give up after a match and have another > > driver give a device a shot. > > I think it just needs to be tried out... Oh yeah, it would definitely work and would be a lot nicer. I'll rework this. -Saravana