linux-kernel - Re: [PATCH v3 2/3] drivers: bus: simple-pm-bus: Use clocks

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Date:   Fri, 12 Aug 2022 20:25:20 +0800
From:   Liu Ying <victor.liu@....com>
To:     Geert Uytterhoeven <geert@...ux-m68k.org>
Cc:     "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
        <devicetree@...r.kernel.org>,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Shawn Guo <shawnguo@...nel.org>,
        Sascha Hauer <s.hauer@...gutronix.de>,
        Sascha Hauer <kernel@...gutronix.de>,
        Fabio Estevam <festevam@...il.com>,
        NXP Linux Team <linux-imx@....com>,
        Saravana Kannan <saravanak@...gle.com>,
        Greg KH <gregkh@...uxfoundation.org>,
        Geert Uytterhoeven <geert+renesas@...der.be>,
        Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>,
        Rob Herring <robh@...nel.org>
Subject: Re: [PATCH v3 2/3] drivers: bus: simple-pm-bus: Use clocks

Hi Geert,

On Fri, 2022-08-12 at 11:49 +0200, Geert Uytterhoeven wrote:
> On Thu, Aug 4, 2022 at 8:10 AM Liu Ying <victor.liu@....com> wrote:
> > Simple Power-Managed bus controller may need functional clock(s)
> > to be enabled before child devices connected to the bus can be
> > accessed.  Get the clock(s) as a bulk and enable/disable the
> > clock(s) when the bus is being power managed.
> > 
> > One example is that Freescale i.MX8qxp pixel link MSI bus
> > controller
> > needs MSI clock and AHB clock to be enabled before accessing child
> > devices.
> > 
> > Signed-off-by: Liu Ying <victor.liu@....com>
> > ---
> > v1->v3:
> > * No change.
> 
> Thanks for your patch!
> 
> > --- a/drivers/bus/simple-pm-bus.c
> > +++ b/drivers/bus/simple-pm-bus.c
> > @@ -72,6 +89,42 @@ static int simple_pm_bus_remove(struct
> > platform_device *pdev)
> >         return 0;
> >  }
> > 
> > +static int simple_pm_bus_runtime_suspend(struct device *dev)
> > +{
> > +       struct simple_pm_bus *bus = dev_get_drvdata(dev);
> > +
> > +       if (!bus)
> > +               return 0;
> 
> Can this really happen?

Good question. Should not happen in any cases. pm_runtime_init() sets 
runtime_status to RPM_SUSPENDED and needs_force_resume to 0, so
simple_pm_bus_runtime_{suspend,resume} are only called for
simple-pm-bus, not the others. Unless I miss something, I would remove
the check here and ...

> 
> > +
> > +       clk_bulk_disable_unprepare(bus->num_clks, bus->clks);
> > +
> > +       return 0;
> > +}
> > +
> > +static int simple_pm_bus_runtime_resume(struct device *dev)
> > +{
> > +       struct simple_pm_bus *bus = dev_get_drvdata(dev);
> > +       int ret;
> > +
> > +       if (!bus)
> > +               return 0;
> 
> Likewise.

... here.

> 
> > +
> > +       ret = clk_bulk_prepare_enable(bus->num_clks, bus->clks);
> > +       if (ret) {
> > +               dev_err(dev, "failed to enable clocks: %d\n", ret);
> > +               return ret;
> > +       }
> > +
> > +       return 0;
> > +}
> 
> The rest LGTM, so
> Reviewed-by: Geert Uytterhoeven <geert+renesas@...der.be>

Thanks,
Liu Ying