linux-kernel - Re: [PATCH v4 8/8] clk: Mark fwnodes when their clock provider is added/removed

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Date:   Mon, 8 Feb 2021 15:34:57 -0800
From:   Saravana Kannan <saravanak@...gle.com>
To:     Rob Herring <robh+dt@...nel.org>
Cc:     Jonathan Corbet <corbet@....net>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        Kevin Hilman <khilman@...nel.org>,
        Ulf Hansson <ulf.hansson@...aro.org>,
        Len Brown <len.brown@...el.com>, Len Brown <lenb@...nel.org>,
        Pavel Machek <pavel@....cz>,
        Michael Turquette <mturquette@...libre.com>,
        Stephen Boyd <sboyd@...nel.org>,
        Frank Rowand <frowand.list@...il.com>,
        Marc Zyngier <maz@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Linux Doc Mailing List <linux-doc@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "open list:THERMAL" <linux-pm@...r.kernel.org>,
        linux-clk <linux-clk@...r.kernel.org>,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
        <devicetree@...r.kernel.org>,
        "open list:ACPI FOR ARM64 (ACPI/arm64)" <linux-acpi@...r.kernel.org>,
        Marek Szyprowski <m.szyprowski@...sung.com>,
        Geert Uytterhoeven <geert@...ux-m68k.org>,
        Android Kernel Team <kernel-team@...roid.com>
Subject: Re: [PATCH v4 8/8] clk: Mark fwnodes when their clock provider is added/removed

On Mon, Feb 8, 2021 at 7:39 AM Rob Herring <robh+dt@...nel.org> wrote:
>
> On Fri, Feb 5, 2021 at 4:27 PM Saravana Kannan <saravanak@...gle.com> wrote:
> >
> > This allows fw_devlink to recognize clock provider drivers that don't
> > use the device-driver model to initialize the device. fw_devlink will
> > use this information to make sure consumers of such clock providers
> > aren't indefinitely blocked from probing, waiting for the power domain
> > device to appear and bind to a driver.
>
> Don't we have cases that are a mixture? IOW, a subset of the clock
> provider is initialized early, then the full driver takes over. You'd
> want consumers that are not a driver to succeed, but drivers to defer
> until the full driver is up.

You probably just made a typo, but to clarify, this is about ignoring
suppliers that never bind. So, in your case the clock device is the
supplier.

To answer your question, consumer devices added after the full
supplier driver takes over will still have device links created to the
supplier clock device. But consumers added before the full driver
takes over won't. So, nothing is worse off with fw_devlink=on and we
get way more dependency tracking (device links) created than what we
have today.

-Saravana