From: "Rafael J. Wysocki" <rjw@rjwysocki.net>
To: Ulf Hansson <ulf.hansson@linaro.org>
Cc: Sudeep Holla <sudeep.holla@arm.com>,
Lorenzo Pieralisi <Lorenzo.Pieralisi@arm.com>,
Mark Rutland <mark.rutland@arm.com>,
linux-pm@vger.kernel.org, Kevin Hilman <khilman@kernel.org>,
Lina Iyer <ilina@codeaurora.org>,
Lina Iyer <lina.iyer@linaro.org>,
Rob Herring <robh+dt@kernel.org>,
Daniel Lezcano <daniel.lezcano@linaro.org>,
Thomas Gleixner <tglx@linutronix.de>,
Vincent Guittot <vincent.guittot@linaro.org>,
Stephen Boyd <sboyd@kernel.org>, Juri Lelli <juri.lelli@arm.com>,
Geert Uytterhoeven <geert+renesas@glider.be>,
linux-arm-kernel@lists.infradead.org,
linux-arm-msm@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH v8 09/26] kernel/cpu_pm: Manage runtime PM in the idle path for CPUs
Date: Wed, 18 Jul 2018 12:11:06 +0200 [thread overview]
Message-ID: <2056372.NMt4aPaF4h@aspire.rjw.lan> (raw)
In-Reply-To: <20180620172226.15012-10-ulf.hansson@linaro.org>
On Wednesday, June 20, 2018 7:22:09 PM CEST Ulf Hansson wrote:
> To allow CPUs being power managed by PM domains, let's deploy support for
> runtime PM for the CPU's corresponding struct device.
>
> More precisely, at the point when the CPU is about to enter an idle state,
> decrease the runtime PM usage count for its corresponding struct device,
> via calling pm_runtime_put_sync_suspend(). Then, at the point when the CPU
> resumes from idle, let's increase the runtime PM usage count, via calling
> pm_runtime_get_sync().
>
> Cc: Lina Iyer <ilina@codeaurora.org>
> Co-developed-by: Lina Iyer <lina.iyer@linaro.org>
> Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
I finally got to this one, sorry for the huge delay.
Let me confirm that I understand the code flow correctly.
> ---
> kernel/cpu_pm.c | 11 +++++++++++
> 1 file changed, 11 insertions(+)
>
> diff --git a/kernel/cpu_pm.c b/kernel/cpu_pm.c
> index 67b02e138a47..492d4a83dca0 100644
> --- a/kernel/cpu_pm.c
> +++ b/kernel/cpu_pm.c
> @@ -16,9 +16,11 @@
> */
>
> #include <linux/kernel.h>
> +#include <linux/cpu.h>
> #include <linux/cpu_pm.h>
> #include <linux/module.h>
> #include <linux/notifier.h>
> +#include <linux/pm_runtime.h>
> #include <linux/spinlock.h>
> #include <linux/syscore_ops.h>
>
> @@ -91,6 +93,7 @@ int cpu_pm_enter(void)
This is called from a cpuidle driver's ->enter callback for the target state
selected by the idle governor ->
> {
> int nr_calls;
> int ret = 0;
> + struct device *dev = get_cpu_device(smp_processor_id());
>
> ret = cpu_pm_notify(CPU_PM_ENTER, -1, &nr_calls);
> if (ret)
> @@ -100,6 +103,9 @@ int cpu_pm_enter(void)
> */
> cpu_pm_notify(CPU_PM_ENTER_FAILED, nr_calls - 1, NULL);
>
> + if (!ret && dev && dev->pm_domain)
> + pm_runtime_put_sync_suspend(dev);
-> so this is going to invoke genpd_runtime_suspend() if the usage
counter of dev is 0.
That will cause cpu_power_down_ok() to be called (because this is
a CPU domain) and that will walk the domain cpumask and compute the
estimated idle duration as the minimum of tick_nohz_get_next_wakeup()
values over the CPUs in that cpumask. [Note that the weight of the
cpumask must be seriously limited for that to actually work, as this
happens in the idle path.] Next, it will return "true" if it can
find a domain state with residency within the estimated idle
duration. [Note that this sort of overlaps with the idle governor's
job.]
Next, __genpd_runtime_suspend() will be invoked to run the device-specific
callback if any [Note that this has to be suitable for the idle path if
present.] and genpd_stop_dev() runs (which, again, may invoke a callback)
and genpd_power_off() runs under the domain lock (which must be a spinlock
then).
> +
> return ret;
> }
> EXPORT_SYMBOL_GPL(cpu_pm_enter);
> @@ -118,6 +124,11 @@ EXPORT_SYMBOL_GPL(cpu_pm_enter);
> */
> int cpu_pm_exit(void)
> {
> + struct device *dev = get_cpu_device(smp_processor_id());
> +
> + if (dev && dev->pm_domain)
> + pm_runtime_get_sync(dev);
> +
> return cpu_pm_notify(CPU_PM_EXIT, -1, NULL);
> }
> EXPORT_SYMBOL_GPL(cpu_pm_exit);
>
And this is called on wakeup when the cpuidle driver's ->enter callback
is about to return and it reverses the suspend flow (except that the
governor doesn't need to be called now).
Have I got that right?
next prev parent reply other threads:[~2018-07-18 10:12 UTC|newest]
Thread overview: 74+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-06-20 17:22 [PATCH v8 00/26] PM / Domains: Support hierarchical CPU arrangement (PSCI/ARM) Ulf Hansson
2018-06-20 17:22 ` [PATCH v8 01/26] PM / Domains: Don't treat zero found compatible idle states as an error Ulf Hansson
2018-06-20 17:22 ` [PATCH v8 02/26] PM / Domains: Deal with multiple states but no governor in genpd Ulf Hansson
2018-06-20 17:22 ` [PATCH v8 03/26] PM / Domains: Add generic data pointer to genpd_power_state struct Ulf Hansson
2018-06-24 21:09 ` Rafael J. Wysocki
2018-06-25 8:34 ` Ulf Hansson
2018-06-20 17:22 ` [PATCH v8 04/26] PM / Domains: Add support for CPU devices to genpd Ulf Hansson
2018-07-19 10:25 ` Rafael J. Wysocki
2018-08-03 11:43 ` Ulf Hansson
2018-08-06 9:36 ` Rafael J. Wysocki
2018-08-24 6:47 ` Ulf Hansson
2018-09-14 9:26 ` Rafael J. Wysocki
2018-06-20 17:22 ` [PATCH v8 05/26] PM / Domains: Add helper functions to attach/detach CPUs to/from genpd Ulf Hansson
2018-07-19 10:22 ` Rafael J. Wysocki
2018-08-03 11:44 ` Ulf Hansson
2018-06-20 17:22 ` [PATCH v8 06/26] timer: Export next wakeup time of a CPU Ulf Hansson
2018-07-19 10:15 ` Rafael J. Wysocki
2018-06-20 17:22 ` [PATCH v8 07/26] PM / Domains: Add genpd governor for CPUs Ulf Hansson
2018-07-19 10:32 ` Rafael J. Wysocki
2018-07-26 9:14 ` Rafael J. Wysocki
2018-08-03 14:28 ` Ulf Hansson
2018-08-06 9:20 ` Rafael J. Wysocki
2018-08-09 15:39 ` Lorenzo Pieralisi
2018-08-24 9:26 ` Ulf Hansson
2018-08-24 10:38 ` Lorenzo Pieralisi
2018-08-30 13:36 ` Ulf Hansson
2018-09-13 15:37 ` Lorenzo Pieralisi
2018-09-14 9:50 ` Rafael J. Wysocki
2018-09-14 10:44 ` Lorenzo Pieralisi
2018-09-14 11:34 ` Rafael J. Wysocki
2018-09-14 12:30 ` Lorenzo Pieralisi
2018-08-24 8:29 ` Ulf Hansson
2018-06-20 17:22 ` [PATCH v8 08/26] PM / Domains: Extend genpd CPU governor to cope with QoS constraints Ulf Hansson
2018-07-19 10:35 ` Rafael J. Wysocki
2018-08-03 11:42 ` Ulf Hansson
2018-06-20 17:22 ` [PATCH v8 09/26] kernel/cpu_pm: Manage runtime PM in the idle path for CPUs Ulf Hansson
2018-07-18 10:11 ` Rafael J. Wysocki [this message]
2018-07-19 10:12 ` Rafael J. Wysocki
2018-07-19 10:39 ` Rafael J. Wysocki
2018-08-03 11:42 ` Ulf Hansson
2018-08-06 9:37 ` Rafael J. Wysocki
2018-08-08 10:56 ` Lorenzo Pieralisi
2018-08-08 18:02 ` Lina Iyer
2018-08-09 8:16 ` Rafael J. Wysocki
2018-08-10 20:36 ` Lina Iyer
2018-08-12 9:53 ` Rafael J. Wysocki
2018-08-09 9:58 ` Sudeep Holla
2018-08-09 10:25 ` Lorenzo Pieralisi
2018-08-10 20:18 ` Lina Iyer
2018-08-15 10:44 ` Lorenzo Pieralisi
2018-08-24 12:24 ` Ulf Hansson
2018-06-20 17:22 ` [PATCH v8 10/26] dt: psci: Update DT bindings to support hierarchical PSCI states Ulf Hansson
2018-06-20 17:22 ` [PATCH v8 11/26] of: base: Add of_get_cpu_state_node() to get idle states for a CPU node Ulf Hansson
2018-06-20 17:22 ` [PATCH v8 12/26] cpuidle: dt: Support hierarchical CPU idle states Ulf Hansson
2018-06-20 17:22 ` [PATCH v8 13/26] drivers: firmware: psci: Move psci to separate directory Ulf Hansson
2018-06-20 17:22 ` [PATCH v8 14/26] MAINTAINERS: Update files for PSCI Ulf Hansson
2018-06-20 17:22 ` [PATCH v8 15/26] drivers: firmware: psci: Split psci_dt_cpu_init_idle() Ulf Hansson
2018-06-20 17:22 ` [PATCH v8 16/26] drivers: firmware: psci: Support hierarchical CPU idle states Ulf Hansson
2018-06-20 17:22 ` [PATCH v8 17/26] drivers: firmware: psci: Simplify error path of psci_dt_init() Ulf Hansson
2018-06-20 17:22 ` [PATCH v8 18/26] drivers: firmware: psci: Announce support for OS initiated suspend mode Ulf Hansson
2018-06-20 17:22 ` [PATCH v8 19/26] drivers: firmware: psci: Prepare to use " Ulf Hansson
2018-06-20 17:22 ` [PATCH v8 20/26] drivers: firmware: psci: Share a few internal PSCI functions Ulf Hansson
2018-06-20 17:22 ` [PATCH v8 21/26] drivers: firmware: psci: Add support for PM domains using genpd Ulf Hansson
2018-06-20 17:22 ` [PATCH v8 22/26] drivers: firmware: psci: Introduce psci_dt_topology_init() Ulf Hansson
2018-06-20 17:22 ` [PATCH v8 23/26] drivers: firmware: psci: Try to attach CPU devices to their PM domains Ulf Hansson
2018-06-20 17:22 ` [PATCH v8 24/26] drivers: firmware: psci: Deal with CPU hotplug when using OSI mode Ulf Hansson
2018-11-19 19:50 ` Raju P L S S S N
2018-11-20 9:50 ` Ulf Hansson
2018-11-20 10:47 ` Raju P L S S S N
2018-06-20 17:22 ` [PATCH v8 25/26] arm64: kernel: Respect the hierarchical CPU topology in DT for PSCI Ulf Hansson
2018-06-20 17:22 ` [PATCH v8 26/26] arm64: dts: Convert to the hierarchical CPU topology layout for MSM8916 Ulf Hansson
2018-07-03 5:44 ` [PATCH v8 00/26] PM / Domains: Support hierarchical CPU arrangement (PSCI/ARM) Ulf Hansson
2018-07-03 7:54 ` Rafael J. Wysocki
2018-07-09 11:42 ` Ulf Hansson
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