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From:   Marcin Wojtas <mw@semihalf.com>
Date:   Thu, 28 Jul 2022 08:47:58 +0200
Message-ID: <CAPv3WKcc2i6HsraP3OSrFY0YiBOAHwBPxJUErg_0p7mpGjn3Ug@mail.gmail.com>
Subject: Re: [net-next: PATCH v3 6/8] net: core: switch to fwnode_find_net_device_by_node()
To:     Vladimir Oltean <olteanv@gmail.com>
Cc:     Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        ACPI Devel Maling List <linux-acpi@vger.kernel.org>,
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        Landen Chao <Landen.Chao@mediatek.com>,
        Linus Walleij <linus.walleij@linaro.org>,
        Andrew Lunn <andrew@lunn.ch>,
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=C5=9Br., 27 lip 2022 o 23:11 Vladimir Oltean <olteanv@gmail.com> napisa=C5=
=82(a):
>
> On Wed, Jul 27, 2022 at 07:40:00PM +0200, Marcin Wojtas wrote:
> > SET_NETDEV_DEV() fills net_device->dev.parent with &pdev->dev
> > and in most cases it is sufficient apparently it is sufficient for
> > fwnode_find_parent_dev_match (at least tests with mvneta case proves
> > it's fine).
>
> Indeed, mvneta works, which is a plain old platform device that hasn't
> even been converted to fwnode, so why don't the others?
>
> Well, as it turns out, it's one of the cases where I spoke to soon,
> thinking I knew what was the problem why probing failed, before actually
> debugging.
>
> I thought there was no dmesg output from DSA at all, which would have
> indicated an eternal -EPROBE_DEFER situation. But there's one tiny line
> I had overlooked:
>
> [    5.094013] mscc_felix 0000:00:00.5: error -EINVAL: Failed to register=
 DSA switch
>
> This comes from here:
>
> static int dsa_port_parse_fw(struct dsa_port *dp, struct fwnode_handle *f=
wnode)
> {
>         struct fwnode_handle *ethernet =3D fwnode_find_reference(fwnode, =
"ethernet", 0);
>         bool link =3D fwnode_property_present(fwnode, "link");
>         const char *name =3D NULL;
>         int ret;
>
>         ret =3D fwnode_property_read_string(fwnode, "label", &name);
> //      if (ret)
> //              return ret;
>
>         dp->fwnode =3D fwnode;
>
> The 'label' property of a port was optional, you've made it mandatory by =
accident.
> It is used only by DSA drivers that register using platform data.

Thanks for spotting that, I will make it optional again.

>
> (side note, I can't believe you actually have a 'label' property for the
> CPU port and how many people are in the same situation as you; you know
> it isn't used for anything, right? how do we stop the cargo cult?)
>

Well, given these results:
~/git/linux : git grep 'label =3D \"cpu\"' arch/arm/boot/dts/ | wc -l
79
~/git/linux : git grep 'label =3D \"cpu\"' arch/arm64/boot/dts/ | wc -l
14

It's not a surprise I also have it defined in the platforms I test. I
agree it doesn't serve any purpose in terms of creating the devices in
DSA with DT, but it IMO increases readability of the description at
least.

> > Can you please check applying following diff:
> >
> > --- a/drivers/base/property.c
> > +++ b/drivers/base/property.c
> > @@ -695,20 +695,22 @@ EXPORT_SYMBOL_GPL(fwnode_get_nth_parent);
> >   * The routine can be used e.g. as a callback for class_find_device().
> >   *
> >   * Returns: %1 - match is found
> >   *          %0 - match not found
> >   */
> >  int fwnode_find_parent_dev_match(struct device *dev, const void *data)
> >  {
> >         for (; dev; dev =3D dev->parent) {
> >                 if (device_match_fwnode(dev, data))
> >                         return 1;
> > +               else if (device_match_of_node(dev, to_of_node(data))
> > +                       return 1;
> >         }
> >
> >         return 0;
> >  }
> >  EXPORT_SYMBOL_GPL(fwnode_find_parent_dev_match);
>
> So, nothing to do with device_match_fwnode() failing, that would have
> been strange, come to think about it. Sorry for the noise here.
>

Great, thank you for confirmation.

> But looking at the deeper implementation of dev_fwnode() as:
>
> struct fwnode_handle *dev_fwnode(struct device *dev)
> {
>         return IS_ENABLED(CONFIG_OF) && dev->of_node ?
>                 of_fwnode_handle(dev->of_node) : dev->fwnode;
> }
>
> I wonder, why did you have to modify mvpp2? It looks at dev->of_node
> prior to returning dev->fwnode. It should work.

When I boot with ACPI, the dev->of_node becomes NULL. With DT it's fine as-=
is.

Best regards,
Marcin