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SubjectRe: [PATCH 2/3] cpufreq: Implement freq-constraint callback
On Thu, Jan 17, 2019 at 05:46:32PM -0800, Matthias Kaehlcke wrote:
> On Fri, Jan 11, 2019 at 02:48:35PM +0530, Viresh Kumar wrote:
> > This implements the frequency constraint callback and registers it with
> > the freq-constraint framework whenever a policy is created. On policy
> > removal the callback is unregistered.
> >
> > The constraints are also taken into consideration in
> > cpufreq_set_policy().
> >
> > No constraints are added until now though.
>
> nit: 'for now'?
>
> > Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
> > ---
> > drivers/cpufreq/Kconfig | 1 +
> > drivers/cpufreq/cpufreq.c | 44 ++++++++++++++++++++++++++++++++++++++++++++
> > 2 files changed, 45 insertions(+)
> >
> > diff --git a/drivers/cpufreq/Kconfig b/drivers/cpufreq/Kconfig
> > index 608af20a3494..2c2842cf2734 100644
> > --- a/drivers/cpufreq/Kconfig
> > +++ b/drivers/cpufreq/Kconfig
> > @@ -2,6 +2,7 @@ menu "CPU Frequency scaling"
> >
> > config CPU_FREQ
> > bool "CPU Frequency scaling"
> > + select DEVICE_FREQ_CONSTRAINT
> > select SRCU
> > help
> > CPU Frequency scaling allows you to change the clock speed of
> > diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
> > index a8fa684f5f90..63028612d011 100644
> > --- a/drivers/cpufreq/cpufreq.c
> > +++ b/drivers/cpufreq/cpufreq.c
> > @@ -21,6 +21,7 @@
> > #include <linux/cpufreq.h>
> > #include <linux/delay.h>
> > #include <linux/device.h>
> > +#include <linux/freq_constraint.h>
> > #include <linux/init.h>
> > #include <linux/kernel_stat.h>
> > #include <linux/module.h>
> > @@ -1163,6 +1164,7 @@ static void cpufreq_policy_free(struct cpufreq_policy *policy)
> > per_cpu(cpufreq_cpu_data, cpu) = NULL;
> > write_unlock_irqrestore(&cpufreq_driver_lock, flags);
> >
> > + freq_constraint_remove_cpumask_callback(policy->related_cpus);
> > cpufreq_policy_put_kobj(policy);
> > free_cpumask_var(policy->real_cpus);
> > free_cpumask_var(policy->related_cpus);
> > @@ -1170,6 +1172,24 @@ static void cpufreq_policy_free(struct cpufreq_policy *policy)
> > kfree(policy);
> > }
> >
> > +static void freq_constraint_callback(void *param)
> > +{
> > + struct cpufreq_policy *policy = param;
> > + struct cpufreq_policy new_policy = *policy;
> > +
> > + new_policy.min = policy->user_policy.min;
> > + new_policy.max = policy->user_policy.max;
> > +
> > + down_write(&policy->rwsem);
> > + if (policy_is_inactive(policy))
> > + goto unlock;
> > +
> > + cpufreq_set_policy(policy, &new_policy);
> > +
> > +unlock:
> > + up_write(&policy->rwsem);
> > +}
> > +
> > static int cpufreq_online(unsigned int cpu)
> > {
> > struct cpufreq_policy *policy;
> > @@ -1236,6 +1256,14 @@ static int cpufreq_online(unsigned int cpu)
> > per_cpu(cpufreq_cpu_data, j) = policy;
> > add_cpu_dev_symlink(policy, j);
> > }
> > +
> > + ret = freq_constraint_set_cpumask_callback(policy->related_cpus,
> > + freq_constraint_callback, policy);
> > + if (ret) {
> > + pr_err("Failed to set freq-constraints: %d (%*pbl)\n",
> > + ret, cpumask_pr_args(policy->cpus));
> > + goto out_destroy_policy;
> > + }
> > } else {
> > policy->min = policy->user_policy.min;
> > policy->max = policy->user_policy.max;
> > @@ -2198,6 +2226,8 @@ static int cpufreq_set_policy(struct cpufreq_policy *policy,
> > struct cpufreq_policy *new_policy)
> > {
> > struct cpufreq_governor *old_gov;
> > + struct device *cpu_dev = get_cpu_device(policy->cpu);
> > + unsigned long fc_min, fc_max;
> > int ret;
> >
> > pr_debug("setting new policy for CPU %u: %u - %u kHz\n",
> > @@ -2217,6 +2247,20 @@ static int cpufreq_set_policy(struct cpufreq_policy *policy,
> > if (ret)
> > return ret;
> >
> > + ret = freq_constraints_get(cpu_dev, &fc_min, &fc_max);
> > + if (ret) {
> > + dev_err(cpu_dev, "cpufreq: Failed to get freq-constraints\n");
> > + } else {
> > + if (fc_min > new_policy->min)
> > + new_policy->min = fc_min;
> > + if (fc_max < new_policy->max)
> > + new_policy->max = fc_max;
> > + }
>
> nit: for if/else constructs with a typical and an 'exception' case
> IMO it is usually more readable when the normal case is handled in the
> 'if' branch (first) and the exception in 'else'.

Forgot to add this:

Reviewed-by: Matthias Kaehlcke <mka@chromium.org>

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