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

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Message-ID: <CAMuHMdX7OxTjwQmdP8xDbVkjtZ5442qFao8K6bNpDQ5S3GPSgQ@mail.gmail.com>
Date:   Tue, 30 Mar 2021 08:58:23 +0200
From:   Geert Uytterhoeven <geert@...ux-m68k.org>
To:     Stephen Boyd <sboyd@...nel.org>
Cc:     Saravana Kannan <saravanak@...gle.com>,
        Marek Szyprowski <m.szyprowski@...sung.com>,
        Nicolas Saenz Julienne <nsaenzjulienne@...e.de>,
        Tudor Ambarus <tudor.ambarus@...rochip.com>,
        Jonathan Corbet <corbet@....net>,
        Frank Rowand <frowand.list@...il.com>,
        Greg KH <gregkh@...uxfoundation.org>,
        Kevin Hilman <khilman@...nel.org>,
        Len Brown <len.brown@...el.com>, Len Brown <lenb@...nel.org>,
        Marc Zyngier <maz@...nel.org>,
        Michael Turquette <mturquette@...libre.com>,
        Pavel Machek <pavel@....cz>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        Rob Herring <robh+dt@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ulf Hansson <ulf.hansson@...aro.org>,
        Nicolas Ferre <nicolas.ferre@...rochip.com>,
        Claudiu Beznea <claudiu.beznea@...rochip.com>,
        DOCUMENTATION <linux-doc@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Linux PM list <linux-pm@...r.kernel.org>,
        linux-clk <linux-clk@...r.kernel.org>,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS <devicetre
        e@...r.kernel.org>, ACPI Devel Maling List <linux-acpi@...r.kernel.org>,
        Android Kernel Team <kernel-team@...roid.com>, linux-rpi-kernel" 
        <linux-rpi-kernel@...ts.infradead.org>
Subject: Re: [PATCH] clk: Mark fwnodes when their clock provider is added

Hi Stephen,

On Tue, Mar 30, 2021 at 3:53 AM Stephen Boyd <sboyd@...nel.org> wrote:
> Quoting Saravana Kannan (2021-03-29 16:28:20)
> > On Mon, Mar 29, 2021 at 2:25 PM Stephen Boyd <sboyd@...nel.org> wrote:
> > > Quoting Geert Uytterhoeven (2021-03-26 11:29:55)
> > > > On Fri, Mar 26, 2021 at 7:13 PM Stephen Boyd <sboyd@...nel.org> wrote:
> > > > > Quoting Nicolas Saenz Julienne (2021-03-25 11:25:24)
> > > > > > >
> > > > > > > This patch mainly revealed that clk/bcm/clk-raspberrypi.c driver calls
> > > > > > > devm_of_clk_add_hw_provider(), with a device pointer, which has a NULL
> > > > > > > dev->of_node. I'm not sure if adding a check for a NULL np in
> > > > > > > of_clk_add_hw_provider() is a right fix, though.
> > > > > >
> > > > > > I believe the right fix is not to call 'devm_of_clk_add_hw_provider()' if
> > > > > > 'pdev->dev.of_node == NULL'. In such case, which is RPi3's, only the CPU clock
> > > > > > is used, and it's defined and queried later through
> > > > > > devm_clk_hw_register_clkdev().
> > > > > >
> > > > > > @Marek, I don't mind taking care of it if it's OK with you.
> > > > > >
> > > > >
> > > > > Ah I see this is related to the patch I just reviewed. Can you reference
> > > > > this in the commit text? And instead of putting the change into the clk
> > > > > provider let's check for NULL 'np' in of_clk_add_hw_provider() instead
> > > > > and return 0 if there's nothing to do. That way we don't visit this
> > > > > problem over and over again.
> > > >
> > > > I'm not sure the latter is what we reall want: shouldn't calling
> > > > *of*_clk_add_hw_provider() with a NULL np be a bug in the provider?
> > > >
> > >
> > > I don't have a strong opinion either way. Would it be useful if the
> > > function returned an error when 'np' is NULL?
> >
> > I lean towards returning an error. Not a strong opinion either.
>
> Does it have any use?

of_clk_del_provider() removes the first provider found with node == NULL.
If there are two drivers calling of_clk_add_hw_provider(), and one of
hem calls of_clk_del_provider() later, the wrong provider may be
removed from the list.

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds