Messages in this thread | | | From | Geert Uytterhoeven <> | Date | Fri, 9 Jul 2021 15:57:56 +0200 | Subject | Re: [PATCH] PM: domains: Don't attach a device to genpd that corresponds to a provider |
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Hi Ulf,
On Fri, Jul 9, 2021 at 3:48 PM Ulf Hansson <ulf.hansson@linaro.org> wrote: > On Fri, 9 Jul 2021 at 15:35, Geert Uytterhoeven <geert@linux-m68k.org> wrote: > > On Fri, Jul 9, 2021 at 3:23 PM Ulf Hansson <ulf.hansson@linaro.org> wrote: > > > On Fri, 9 Jul 2021 at 15:07, Geert Uytterhoeven <geert@linux-m68k.org> wrote: > > > > On Fri, Jul 9, 2021 at 2:56 PM Ulf Hansson <ulf.hansson@linaro.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. > > > > Ah, you're worried about the case where the subdomain is a child of > > the parent domain, but the actual subdomain controller (represented > > by the platform device) isn't? > > Well, even if the platform device represents a subdomain controller, > should it really be attached to the parent domain?
That's what the presence of the "power-domains" property means, isn't it? If the subdomain controller itself is not part of the parent power domain, there should not be a "power-domains" property. So perhaps we need a new property ("power-domain-parent"?) to indicate what is the parent domain for the subdomains in this case?
> In any case, it means that the provider needs to manage runtime PM, > etc for its struct device to not prevent the parent domain from being > powered off.
Shouldn't all drivers for devices that can be somewhere in a PM Domain hierarchy do that anyway? :-) See e.g. commit 3a611e26e958b037 ("net/smsc911x: Add minimal runtime PM support").
If "simple-bus" would do that, we could get rid of "simple-pm-bus"...
Gr{oetje,eeting}s,
Geert
-- Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org
In personal conversations with technical people, I call myself a hacker. But when I'm talking to journalists I just say "programmer" or something like that. -- Linus Torvalds
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