linux-kernel - Re: [PATCH 2/5] memory: fsl_ifc: populate child devices without relying on simple-bus

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Date:   Fri, 8 Oct 2021 22:12:13 -0500
From:   Li Yang <leoyang.li@....com>
To:     Rob Herring <robh@...nel.org>
Cc:     "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
        <devicetree@...r.kernel.org>, Shawn Guo <shawnguo@...nel.org>,
        lkml <linux-kernel@...r.kernel.org>,
        Krzysztof Kozlowski <krzk@...nel.org>,
        linuxppc-dev <linuxppc-dev@...ts.ozlabs.org>,
        "moderated list:ARM/FREESCALE IMX / MXC ARM ARCHITECTURE" 
        <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH 2/5] memory: fsl_ifc: populate child devices without
 relying on simple-bus

On Mon, Oct 4, 2021 at 12:14 PM Rob Herring <robh@...nel.org> wrote:
>
> On Thu, Sep 30, 2021 at 07:09:21PM -0500, Li Yang wrote:
> > After we update the binding to not use simple-bus compatible for the
> > controller, we need the driver to populate the child devices explicitly.
> >
> > Signed-off-by: Li Yang <leoyang.li@....com>
> > ---
> >  drivers/memory/fsl_ifc.c | 9 +++++++++
> >  1 file changed, 9 insertions(+)
> >
> > diff --git a/drivers/memory/fsl_ifc.c b/drivers/memory/fsl_ifc.c
> > index d062c2f8250f..251d713cd50b 100644
> > --- a/drivers/memory/fsl_ifc.c
> > +++ b/drivers/memory/fsl_ifc.c
> > @@ -88,6 +88,7 @@ static int fsl_ifc_ctrl_remove(struct platform_device *dev)
> >  {
> >       struct fsl_ifc_ctrl *ctrl = dev_get_drvdata(&dev->dev);
> >
> > +     of_platform_depopulate(&dev->dev);
> >       free_irq(ctrl->nand_irq, ctrl);
> >       free_irq(ctrl->irq, ctrl);
> >
> > @@ -285,6 +286,14 @@ static int fsl_ifc_ctrl_probe(struct platform_device *dev)
> >               }
> >       }
> >
> > +     /* legacy dts may still use "simple-bus" compatible */
> > +     if (!of_device_is_compatible(dev->dev.of_node, "simple-bus")) {
> > +             ret = of_platform_populate(dev->dev.of_node, NULL, NULL,
> > +                                             &dev->dev);
>
> There's no need to make this conditional. of_platform_populate() is safe
> to call multiple times. If that doesn't work, it's a bug.

I think that it is probably an optimization to avoid re-populate the
bus for legacy device trees.  But it might be cleaner to just
re-populate anyway?

Regards,
Leo