linux-kernel - Re: [PATCH] PM: domains: Don't attach a device to genpd that corresponds to a provider

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Date:   Fri, 9 Jul 2021 15:22:27 +0200
From:   Ulf Hansson <ulf.hansson@...aro.org>
To:     Geert Uytterhoeven <geert@...ux-m68k.org>
Cc:     "Rafael J . Wysocki" <rjw@...ysocki.net>,
        Linux PM list <linux-pm@...r.kernel.org>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        Stephen Boyd <sboyd@...nel.org>,
        Saravana Kannan <saravanak@...gle.com>,
        Dmitry Baryshkov <dmitry.baryshkov@...aro.org>,
        Kevin Hilman <khilman@...nel.org>,
        Geert Uytterhoeven <geert+renesas@...der.be>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] PM: domains: Don't attach a device to genpd that
 corresponds to a provider

On Fri, 9 Jul 2021 at 15:07, Geert Uytterhoeven <geert@...ux-m68k.org> wrote:
>
> Hi Ulf,
>
> Thanks for your patch!
>
> On Fri, Jul 9, 2021 at 2:56 PM Ulf Hansson <ulf.hansson@...aro.org> wrote:
> > According to the common power domain DT bindings, a power domain provider
> > must have a "#power-domain-cells" property in its OF node. Additionally, if
> > a provider has a "power-domains" property, it means that it has a parent
> > domain.
>
> OK.
>
> > It has turned out that some OF nodes that represents a genpd provider may
> > also be compatible with a regular platform device. This leads to, during
> > probe, genpd_dev_pm_attach(), genpd_dev_pm_attach_by_name() and
> > genpd_dev_pm_attach_by_id() tries to attach the corresponding struct device
> > to the genpd provider's parent domain, which is wrong. Instead the genpd
>
> Why is that wrong?

It may lead to that the struct device that corresponds to a genpd
provider may be attached to the parent domain. In other words, the
parent domain will not only be controlled by a child domain
(corresponding to the provider), but also through the provider's
struct device. As far as I can tell, this has never been the intent
for how things should work in genpd.

So wrong or not, I guess it depends on what you expect to happen.

Do you see an issue with changing this?

>
> > provider should only assign a parent domain, through
> > pm_genpd_add_subdomain() or of_genpd_add_subdomain().

Kind regards
Uffe