LKML Archive on
help / color / mirror / Atom feed
From: Geert Uytterhoeven <>
To: Kevin Hilman <>
Cc: "Rafael J. Wysocki" <>,
	Eric Anholt <>,
	Ulf Hansson <>,
	"" <>,
	Tomasz Figa <>,
	Greg Kroah-Hartman <>,
	Linux PM list <>
Subject: Re: [PATCH] PM / Domains: If an OF node is found but no device probed yet, defer.
Date: Mon, 16 Mar 2015 09:44:22 +0100	[thread overview]
Message-ID: <> (raw)
In-Reply-To: <>

Hi Kevin,

On Fri, Mar 13, 2015 at 7:01 PM, Kevin Hilman <> wrote:
> Geert Uytterhoeven <> writes:
>> On Wed, Mar 11, 2015 at 11:08 PM, Rafael J. Wysocki <> wrote:
>>> More CCes.
>>> On Wednesday, March 11, 2015 08:27:28 AM Eric Anholt wrote:
>>>> If we've declared a power domain in the OF, and the OF node is found
>>>> but the requested domain hasn't been registered on it yet, then we
>>>> probably have just tried to probe before the power domain driver has.
>>>> Defer our device's probe until it shows up.
>>>> Signed-off-by: Eric Anholt <>
>>> Kevin, Ulf, any chance to have a look at this, please?
>>>> ---
>>>> I ran into this when turning my ad-hoc code for BCM2835 (Raspberry Pi)
>>>> USB poweron support in the DWC2 controller to an OF-based power domain
>>>> declaration.
>> I guess you are initializing the PM domains from module_init()?
>> I use core_initcall() in arch/arm/mach-shmobile/pm-rmobile.c to make sure it's
>> initialized earlier, as e.g. the interrupt controller uses postcore_initcall().
> Yeah, I think most existing users are initizling PM domains early, but IMO
> we should be working towards supporting PM domains that are created
> later as well (as this patch does.)

Sure. When interrupt controllers are involved (yes, they can be in a PM (Clock)
Domain too), there are definitely some complex issues to resolve in the core OF
probing code first. Cfr. the bug mentioned in

>>>> diff --git a/drivers/base/power/domain.c b/drivers/base/power/domain.c
>>>> index ba4abbe..2b93c98 100644
>>>> --- a/drivers/base/power/domain.c
>>>> +++ b/drivers/base/power/domain.c
>>>> @@ -2064,7 +2064,7 @@ EXPORT_SYMBOL_GPL(of_genpd_del_provider);
>>>>  struct generic_pm_domain *of_genpd_get_from_provider(
>>>>                                       struct of_phandle_args *genpdspec)
>>>>  {
>>>> -     struct generic_pm_domain *genpd = ERR_PTR(-ENOENT);
>>>> +     struct generic_pm_domain *genpd = ERR_PTR(-EPROBE_DEFER);
>> Currently platform_drv_probe() just continues if dev_pm_domain_attach() returns
>> a different error than -EPROBE_DEFER, which is what you are seeing.
>> Your change does have the side effect that a new DT with PM domains won't
>> work on an older kernel that doesn't have the PM domain driver yet.
> Is that a real problem though?  Using newer DTs on older kernels can
> cause many types of problems.

It means we cannot describe everything in (stable) DT before all support code
has been implemented. Ignoring that, it enforces strict merge order.



Geert Uytterhoeven -- There's lots of Linux beyond ia32 --

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

  reply	other threads:[~2015-03-16  8:44 UTC|newest]

Thread overview: 9+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2015-03-11 15:27 [PATCH] PM / Domains: If an OF node is found but no device probed yet, defer Eric Anholt
2015-03-11 22:08 ` Rafael J. Wysocki
2015-03-11 22:14   ` Geert Uytterhoeven
2015-03-12 19:31     ` Eric Anholt
2015-03-13 18:01     ` Kevin Hilman
2015-03-16  8:44       ` Geert Uytterhoeven [this message]
2015-03-16 10:12       ` Ulf Hansson
2015-03-18 22:55         ` Eric Anholt
2015-03-12  8:39 ` Ulf Hansson

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \ \ \ \ \ \ \ \ \ \ \

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).