linux-kernel - Re: [PATCH 0/3] cpuidle: updates related to tick_broadcast

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Message-ID: <CAMAWPa_69wXtOAKkerLcXN3AcCMC7oBCH_K3MQ-A7A8nmXQzfQ@mail.gmail.com>
Date:	Wed, 13 May 2015 17:13:27 -0700
From:	Kevin Hilman <khilman@...nel.org>
To:	"Rafael J. Wysocki" <rjw@...ysocki.net>
Cc:	Kevin Hilman <khilman@...nel.org>,
	Daniel Lezcano <daniel.lezcano@...aro.org>,
	Preeti U Murthy <preeti@...ux.vnet.ibm.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	"Rafael J. Wysocki" <rafael.j.wysocki@...el.com>,
	rlippert@...gle.com,
	"linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>,
	Linus Walleij <linus.walleij@...aro.org>,
	lkml <linux-kernel@...r.kernel.org>,
	Ingo Molnar <mingo@...hat.com>,
	Sudeep Holla <sudeep.holla@....com>,
	linuxppc-dev@...ts.ozlabs.org, Lina Iyer <lina.iyer@...aro.org>,
	Ulf Hansson <ulf.hansson@...aro.org>
Subject: Re: [PATCH 0/3] cpuidle: updates related to tick_broadcast_enter() failures

On Wed, May 13, 2015 at 5:16 PM, Rafael J. Wysocki <rjw@...ysocki.net> wrote:
> On Wednesday, May 13, 2015 03:59:55 PM Kevin Hilman wrote:
>> "Rafael J. Wysocki" <rjw@...ysocki.net> writes:
>>
>> [...]
>>
>> > Second, quite honestly, I don't see a connection to genpd here.
>>
>> The connection with genpd is because the *reason* the timer was
>> shutdown/stopped is because it shares power with the CPU, which is why
>> the timer stops when the CPU hits ceratin low power states.  IOW, it's
>> in the same power domain as the CPU.
>
> Well, what if you don't have genpd on that system?  Is the problem at hand not
> relevant then magically?

Well, if you're not using genpd to model hardware power domain
dependencies, then yes you'll definitely need a different solution.

And, as we discussed on IRC.  If you only care about timers, and genpd
is not in use, then $SUBJECT series is a fine approach, and I have no
objections.  But for SoCs where there are several other things that
share power with CPU, we need a more generic, genpd based solution,
which it seems we're in agreement on.  And since the two approaches
are not mutually exclusive, then I have real objections to applying
this series.

Acked-by: Kevin Hilman <khilman@...aro.org>

Kevin
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