From: Nicholas Piggin <npiggin@gmail.com>
To: "Rafael J. Wysocki" <rjw@rjwysocki.net>
Cc: Daniel Lezcano <daniel.lezcano@linaro.org>,
Vaidyanathan Srinivasan <svaidy@linux.vnet.ibm.com>,
linux-pm@vger.kernel.org
Subject: Re: [RFC] cpuidle: menu: nearby timer use lightest state; allow state 0 to be disabled
Date: Mon, 5 Jun 2017 17:40:03 +1000 [thread overview]
Message-ID: <20170605174003.18266685@roar.ozlabs.ibm.com> (raw)
In-Reply-To: <20170530162631.9073-1-npiggin@gmail.com>
On Wed, 31 May 2017 02:26:31 +1000
Nicholas Piggin <npiggin@gmail.com> wrote:
> I've found the menu driver does not allow state0 to properly be disabled
> because of all this poll logic selecting the first state and then trying
> to iterate over subsequent states. Ripping most of that out and simplifying
> it solved that issue but raised more questions about polling logic.
>
> Firstly polling logic is there only on architectures which define
> ARCH_HAS_CPU_RELAX, which is only x86. Seems like if we think a
> timer is so close that no powersave should be done, then surely just
> picking the lightest mode (whether that is polling or something else)
> would be best.
>
> But looking further into it, it seems maybe like some x86 hack (as
> the comments and changelog in 7884084f3bcc and subsequent attempts to
> work around Atom and broken firmware suggests). I would have thought
> such broken hard/firmware should get workarounds applied to fix the
> state values rather than add such logic?
>
> On the other hand, if (CPUIDLE_DRIVER_STATE_START > 0) is shorthand for
> if (x86 hacks), that's fine I'm happy to leave that alone and just work
> with the else parts...
>
> This is just a draft, but it does what I want at least with regard to
> disabling state0 for testing.
Ping, any thoughts on these issues?
Thanks,
Nick
next prev parent reply other threads:[~2017-06-05 7:40 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-05-30 16:26 [RFC] cpuidle: menu: nearby timer use lightest state; allow state 0 to be disabled Nicholas Piggin
2017-06-05 7:40 ` Nicholas Piggin [this message]
2017-06-05 12:58 ` Rafael J. Wysocki
2017-06-05 15:19 ` Gautham R Shenoy
2017-06-06 1:15 ` Nicholas Piggin
2017-06-06 10:04 ` Gautham R Shenoy
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