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Message-ID: <2678403.roXOZuBH3e@aspire.rjw.lan>
Date: Tue, 19 Feb 2019 11:25:30 +0100
From: "Rafael J. Wysocki" <rjw@...ysocki.net>
To: Viresh Kumar <viresh.kumar@...aro.org>
Cc: linux-pm@...r.kernel.org,
Vincent Guittot <vincent.guittot@...aro.org>,
Sudeep Holla <sudeep.holla@....com>,
Marek Szyprowski <m.szyprowski@...sung.com>,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH V4 1/2] cpufreq: Allow light-weight tear down and bring up of CPUs
On Tuesday, February 12, 2019 12:06:04 PM CET Viresh Kumar wrote:
> The cpufreq core doesn't remove the cpufreq policy anymore on CPU
> offline operation, rather that happens when the CPU device gets
> unregistered from the kernel. This allows faster recovery when the CPU
> comes back online. This is also very useful during system wide
> suspend/resume where we offline all non-boot CPUs during suspend and
> then bring them back on resume.
>
> This commit takes the same idea a step ahead to allow drivers to do
> light weight tear-down and bring-up during CPU offline and online
> operations.
>
> A new set of callbacks is introduced, online/offline(). online() gets
> called when the first CPU of an inactive policy is brought up and
> offline() gets called when all the CPUs of a policy are offlined.
>
> The existing init/exit() callback get called on policy
> creation/destruction. They also get called instead of online/offline()
> callbacks if the online/offline() callbacks aren't provided.
>
> This also moves around some code to get executed only for the new-policy
> case going forward.
>
> Signed-off-by: Viresh Kumar <viresh.kumar@...aro.org>
> ---
> V3->V4:
> - Use != instead of ^
>
> drivers/cpufreq/cpufreq.c | 58 +++++++++++++++++++++++++--------------
> include/linux/cpufreq.h | 2 ++
> 2 files changed, 40 insertions(+), 20 deletions(-)
>
> diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
> index 96a69c67a545..55e9795801a4 100644
> --- a/drivers/cpufreq/cpufreq.c
> +++ b/drivers/cpufreq/cpufreq.c
> @@ -1201,28 +1201,39 @@ static int cpufreq_online(unsigned int cpu)
> return -ENOMEM;
> }
>
> - cpumask_copy(policy->cpus, cpumask_of(cpu));
> + if (!new_policy && cpufreq_driver->online) {
> + ret = cpufreq_driver->online(policy);
> + if (ret) {
> + pr_debug("%s: %d: initialization failed\n", __func__,
> + __LINE__);
> + goto out_exit_policy;
> + }
>
> - /* call driver. From then on the cpufreq must be able
> - * to accept all calls to ->verify and ->setpolicy for this CPU
> - */
> - ret = cpufreq_driver->init(policy);
> - if (ret) {
> - pr_debug("initialization failed\n");
> - goto out_free_policy;
> - }
> + /* Recover policy->cpus using related_cpus */
> + cpumask_copy(policy->cpus, policy->related_cpus);
> + } else {
> + cpumask_copy(policy->cpus, cpumask_of(cpu));
>
> - ret = cpufreq_table_validate_and_sort(policy);
> - if (ret)
> - goto out_exit_policy;
> + /*
> + * Call driver. From then on the cpufreq must be able
> + * to accept all calls to ->verify and ->setpolicy for this CPU.
> + */
> + ret = cpufreq_driver->init(policy);
> + if (ret) {
> + pr_debug("%s: %d: initialization failed\n", __func__,
> + __LINE__);
> + goto out_free_policy;
> + }
>
> - down_write(&policy->rwsem);
> + ret = cpufreq_table_validate_and_sort(policy);
> + if (ret)
> + goto out_exit_policy;
>
> - if (new_policy) {
> /* related_cpus should at least include policy->cpus. */
> cpumask_copy(policy->related_cpus, policy->cpus);
> }
>
> + down_write(&policy->rwsem);
> /*
> * affected cpus must always be the one, which are online. We aren't
> * managing offline cpus here.
> @@ -1421,11 +1432,12 @@ static int cpufreq_offline(unsigned int cpu)
> cpufreq_exit_governor(policy);
>
> /*
> - * Perform the ->exit() even during light-weight tear-down,
> - * since this is a core component, and is essential for the
> - * subsequent light-weight ->init() to succeed.
> + * Perform the ->offline() during light-weight tear-down, as
> + * that allows fast recovery when the CPU comes back.
> */
> - if (cpufreq_driver->exit) {
> + if (cpufreq_driver->offline) {
> + cpufreq_driver->offline(policy);
> + } else if (cpufreq_driver->exit) {
> cpufreq_driver->exit(policy);
> policy->freq_table = NULL;
> }
> @@ -1454,8 +1466,13 @@ static void cpufreq_remove_dev(struct device *dev, struct subsys_interface *sif)
> cpumask_clear_cpu(cpu, policy->real_cpus);
> remove_cpu_dev_symlink(policy, dev);
>
> - if (cpumask_empty(policy->real_cpus))
> + if (cpumask_empty(policy->real_cpus)) {
> + /* We did light-weight exit earlier, do full tear down now */
> + if (cpufreq_driver->offline)
> + cpufreq_driver->exit(policy);
> +
> cpufreq_policy_free(policy);
> + }
> }
>
> /**
> @@ -2488,7 +2505,8 @@ int cpufreq_register_driver(struct cpufreq_driver *driver_data)
> driver_data->target) ||
> (driver_data->setpolicy && (driver_data->target_index ||
> driver_data->target)) ||
> - (!!driver_data->get_intermediate != !!driver_data->target_intermediate))
> + (!!driver_data->get_intermediate != !!driver_data->target_intermediate) ||
> + (!driver_data->online != !driver_data->offline))
> return -EINVAL;
>
> pr_debug("trying to register driver %s\n", driver_data->name);
> diff --git a/include/linux/cpufreq.h b/include/linux/cpufreq.h
> index 9db074ecbbd7..b160e98076e3 100644
> --- a/include/linux/cpufreq.h
> +++ b/include/linux/cpufreq.h
> @@ -325,6 +325,8 @@ struct cpufreq_driver {
> /* optional */
> int (*bios_limit)(int cpu, unsigned int *limit);
>
> + int (*online)(struct cpufreq_policy *policy);
> + int (*offline)(struct cpufreq_policy *policy);
> int (*exit)(struct cpufreq_policy *policy);
> void (*stop_cpu)(struct cpufreq_policy *policy);
> int (*suspend)(struct cpufreq_policy *policy);
>
Applied along with the [2/2], thanks!
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