linux-kernel - Re: [PATCH 1/3] dt-bindings: bus: simple-pm-bus: Make clocks and power-domains optional

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Message-ID: <YV85rKlB79nMC+nq@atomide.com>
Date:   Thu, 7 Oct 2021 21:17:16 +0300
From:   Tony Lindgren <tony@...mide.com>
To:     Geert Uytterhoeven <geert@...ux-m68k.org>
Cc:     Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Rob Herring <robh+dt@...nel.org>,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
        <devicetree@...r.kernel.org>,
        "open list:TI ETHERNET SWITCH DRIVER (CPSW)" 
        <linux-omap@...r.kernel.org>, Rob Herring <robh@...nel.org>,
        Simon Horman <horms+renesas@...ge.net.au>,
        Suman Anna <s-anna@...com>
Subject: Re: [PATCH 1/3] dt-bindings: bus: simple-pm-bus: Make clocks and
 power-domains optional

* Geert Uytterhoeven <geert@...ux-m68k.org> [211007 17:57]:
> Hi Tony,
> 
> On Thu, Oct 7, 2021 at 7:24 PM Tony Lindgren <tony@...mide.com> wrote:
> > * Geert Uytterhoeven <geert@...ux-m68k.org> [211007 13:27]:
> > > On Thu, Oct 7, 2021 at 2:49 PM Tony Lindgren <tony@...mide.com> wrote:
> > > > Even without clocks and power domains configured, simple-pm-bus is still
> > > > different from simple-bus as simple-pm-bus enables runtime PM for the bus
> > > > driver.
> > >
> > > Which you need to have working Runtime PM for child devices, right? ;-)
> >
> > Right. And based on what I remember we simply cannot do pm_runtime_enable()
> > for simple-bus without breaking tons of devices.
> 
> Why not? Do you have an example of what would break?
> The only reason I created simple-pm-bus was because the DT people
> objected to adding PM to simple-bus, as they considered it wrong
> conceptually.  AFAIK this wouldn't have caused any actual breakage.

Oh OK, then I just remember the reasons wrong for the need for
adding it as a driver.

Regards,

Tony