linux-kernel - Re: [PATCH v3 1/2] drivers: bus: simple-pm-bus: Add support for probing simple bus only devices

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Date:   Wed, 8 Sep 2021 15:02:21 -0700
From:   Saravana Kannan <saravanak@...gle.com>
To:     Ulf Hansson <ulf.hansson@...aro.org>
Cc:     Russell King <linux@...linux.org.uk>,
        Neil Armstrong <narmstrong@...libre.com>,
        Geert Uytterhoeven <geert+renesas@...der.be>,
        Magnus Damm <magnus.damm@...il.com>,
        Tony Lindgren <tony@...mide.com>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>,
        Damien Le Moal <damien.lemoal@....com>,
        Rob Herring <robh+dt@...nel.org>,
        Android Kernel Team <kernel-team@...roid.com>,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linux-oxnas@...ups.io,
        Linux-Renesas <linux-renesas-soc@...r.kernel.org>,
        linux-omap <linux-omap@...r.kernel.org>,
        linux-riscv <linux-riscv@...ts.infradead.org>
Subject: Re: [PATCH v3 1/2] drivers: bus: simple-pm-bus: Add support for
 probing simple bus only devices

On Tue, Sep 7, 2021 at 3:41 AM Ulf Hansson <ulf.hansson@...aro.org> wrote:
>
> On Sat, 4 Sept 2021 at 02:05, Saravana Kannan <saravanak@...gle.com> wrote:
> >
> > fw_devlink could end up creating device links for bus only devices.
> > However, bus only devices don't get probed and can block probe() or
> > sync_state() [1] call backs of other devices. To avoid this, probe these
> > devices using the simple-pm-bus driver.
> >
> > However, there are instances of devices that are not simple buses (they
> > get probed by their specific drivers) that also list the "simple-bus"
> > (or other bus only compatible strings) in their compatible property to
> > automatically populate their child devices. We still want these devices
> > to get probed by their specific drivers. So, we make sure this driver
> > only probes devices that are only buses.
> >
> > [1] - https://lore.kernel.org/lkml/CAPDyKFo9Bxremkb1dDrr4OcXSpE0keVze94Cm=zrkOVxHHxBmQ@mail.gmail.com/
> > Signed-off-by: Saravana Kannan <saravanak@...gle.com>
> > Tested-by: Saravana Kannan <saravanak@...gle.com>
>
> Reviewed-by: Ulf Hansson <ulf.hansson@...aro.org>
>
> I will run some tests as soon as I can and let you know the results.

Thanks.

-Saravana

>
> Kind regards
> Uffe
>
> > ---
> >  drivers/bus/simple-pm-bus.c | 32 +++++++++++++++++++++++++++++---
> >  1 file changed, 29 insertions(+), 3 deletions(-)
> >
> > diff --git a/drivers/bus/simple-pm-bus.c b/drivers/bus/simple-pm-bus.c
> > index 01a3d0cd08ed..3e086a9f34cb 100644
> > --- a/drivers/bus/simple-pm-bus.c
> > +++ b/drivers/bus/simple-pm-bus.c
> > @@ -13,11 +13,26 @@
> >  #include <linux/platform_device.h>
> >  #include <linux/pm_runtime.h>
> >
> > -
> >  static int simple_pm_bus_probe(struct platform_device *pdev)
> >  {
> > -       const struct of_dev_auxdata *lookup = dev_get_platdata(&pdev->dev);
> > -       struct device_node *np = pdev->dev.of_node;
> > +       const struct device *dev = &pdev->dev;
> > +       const struct of_dev_auxdata *lookup = dev_get_platdata(dev);
> > +       struct device_node *np = dev->of_node;
> > +       const struct of_device_id *match;
> > +
> > +       match = of_match_device(dev->driver->of_match_table, dev);
> > +
> > +       /*
> > +        * These are transparent bus devices (not simple-pm-bus matches) that
> > +        * have their child nodes populated automatically.  So, don't need to
> > +        * do anything more.
> > +        */
> > +       if (match && match->data) {
> > +               if (of_property_match_string(np, "compatible", match->compatible) == 0)
> > +                       return 0;
> > +               else
> > +                       return -ENODEV;
> > +       }
> >
> >         dev_dbg(&pdev->dev, "%s\n", __func__);
> >
> > @@ -31,14 +46,25 @@ static int simple_pm_bus_probe(struct platform_device *pdev)
> >
> >  static int simple_pm_bus_remove(struct platform_device *pdev)
> >  {
> > +       const void *data = of_device_get_match_data(&pdev->dev);
> > +
> > +       if (data)
> > +               return 0;
> > +
> >         dev_dbg(&pdev->dev, "%s\n", __func__);
> >
> >         pm_runtime_disable(&pdev->dev);
> >         return 0;
> >  }
> >
> > +#define ONLY_BUS       ((void *) 1) /* Match if the device is only a bus. */
> > +
> >  static const struct of_device_id simple_pm_bus_of_match[] = {
> >         { .compatible = "simple-pm-bus", },
> > +       { .compatible = "simple-bus",   .data = ONLY_BUS },
> > +       { .compatible = "simple-mfd",   .data = ONLY_BUS },
> > +       { .compatible = "isa",          .data = ONLY_BUS },
> > +       { .compatible = "arm,amba-bus", .data = ONLY_BUS },
> >         { /* sentinel */ }
> >  };
> >  MODULE_DEVICE_TABLE(of, simple_pm_bus_of_match);
> > --
> > 2.33.0.153.gba50c8fa24-goog
> >