From: khilman@kernel•org (Kevin Hilman)
To: linux-arm-kernel@lists•infradead.org
Subject: [PATCH RFC 0/3] PM / Domains: Generic PM domains for cpus
Date: Wed, 10 Jun 2015 10:24:51 -0700 [thread overview]
Message-ID: <7hwpzbo4rg.fsf@deeprootsystems.com> (raw)
In-Reply-To: <1433456946-53296-1-git-send-email-lina.iyer@linaro.org> (Lina Iyer's message of "Thu, 4 Jun 2015 16:29:03 -0600")
Lina Iyer <lina.iyer@linaro•org> writes:
> This is an attempt to provide a generic PM domain for cpus, so as to allow the
> cpu domain to be powered off, when all the cpus are in power down state during
> cpuidle.
You don't use the word "cluster" here, but it might be helpful to
summarize this as using a genpd to model a cluster. A cluster contains
CPUs, but also additional devices/logic like L2$, GIC, PMUs, floating
point units, CoreSight, etc. etc.
> The rationale behind the change is that newer SoCs can power down the
> cpus for very short sleep times to save on leakage power. The domain which
> usually has the cpus, a second level cache and some peripheral hardware is
> powered by a rail that can also be turned off when the cpus are not in
> use.
This last sentence doesn't read well. I think you meant something like:
In the domain which has the CPUs, a second level cache and some
peripheral hardware might share the power rail with the CPUs so could
also be turned off when the cpus are not in use.
> Devices for each cpu, L2 and other related blocks could be attached to the
> domain and when there are no uses of these devices (device idle) the domain
> could also be powered off. Generic PM domains provides all the backend needed
> for such an organization.
>
> In the first 2 patches, I make genpd usable in atomic context as well. CPUIdle
s/as well//
> runs with irqs disabled and therefore use of mutexes in the current genpd
> implementation is a limitation. But, not all PM domains need to operate in irq
> safe context, those that need to can specify explicitly the irq safe
> requirement of the genpd at init. Devices and sub-domains that attach to an irq
> safe genpd also have to be irq safe.
>
> The third patch, adds a generic PM domain for the cpus. GenPD provider can be
drop the ','
A GenPD provider...
> specified in the DT and individual cpus that are part of the domain would be
> the domain consumers. A new API pm_cpu_domain_init() has been introduced that
> would initialize the genpd and attach cpus specified as consumers in the DT to
> the domain.
Hmm, doesn't the of_genpd_* stuff already handle this?
What about non-CPU consumers in the same domain?
> When the cpus enter their idle state cpu_pm notifications are sent
> out for that cpu. The last cpu to send cpu_pm notification would trigger the
> domain power_off callback and the first cpu to come up would trigger the genpd
> power_on callback. Generally, the power_off callback is where the caches are
> flushed in preparation for a power down and the domain hardware configured to
> power down when the cpu finishes execution. In the power_on callback, the
> domain hardware is reset to a state to allow cpus to be active or entire idle
> states individually.
>
> A future addition to this feature, could be a new genpd governor for the
> specific case of the cpu domain. The governor may look up the time available
> to sleep between the last cpu down and the first cpu up, in determining if it
> would be more efficient to just keep the domain powered on.
>
> This patch is based on Ulf's patch for simplifying domain power down states
> [1], which removes a bunch of complexity in genpd, simplifying atomic genpd.
Kevin
prev parent reply other threads:[~2015-06-10 17:24 UTC|newest]
Thread overview: 28+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-06-04 22:29 [PATCH RFC 0/3] PM / Domains: Generic PM domains for cpus Lina Iyer
2015-06-04 22:29 ` [PATCH RFC 1/3] PM / Domains: Allocate memory outside domain locks Lina Iyer
2015-06-07 8:35 ` Krzysztof Kozlowski
2015-06-09 22:45 ` Lina Iyer
2015-06-10 17:33 ` Kevin Hilman
2015-06-04 22:29 ` [PATCH RFC 2/3] PM / Domains: Support atomic PM domains Lina Iyer
2015-06-07 9:21 ` Krzysztof Kozlowski
2015-06-10 16:13 ` Lina Iyer
2015-06-11 0:13 ` Krzysztof Kozlowski
2015-06-11 14:33 ` Lina Iyer
2015-06-10 18:04 ` Kevin Hilman
2015-06-10 20:35 ` Lina Iyer
2015-06-11 9:41 ` Ulf Hansson
2015-06-11 19:47 ` Lina Iyer
2015-06-11 21:13 ` Ulf Hansson
2015-06-04 22:29 ` [PATCH RFC 3/3] PM / Domains: Introduce generic PM domain for cpu domain Lina Iyer
2015-06-07 9:42 ` Krzysztof Kozlowski
2015-06-10 16:57 ` Lina Iyer
2015-06-11 0:27 ` Krzysztof Kozlowski
2015-06-11 14:42 ` Lina Iyer
2015-06-10 17:01 ` Kevin Hilman
2015-06-11 0:35 ` Krzysztof Kozlowski
2015-06-10 21:37 ` Kevin Hilman
2015-06-11 14:56 ` Lina Iyer
2015-06-15 18:43 ` Kevin Hilman
2015-06-15 19:14 ` Lina Iyer
2015-06-16 15:50 ` Kevin Hilman
2015-06-10 17:24 ` Kevin Hilman [this message]
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