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Date: Thu, 06 Nov 2014 16:26:27 +0530
From: Yadwinder Singh Brar <yadi.brar@...sung.com>
To: 'Eduardo Valentin' <edubezval@...il.com>
Cc: linux-pm@...r.kernel.org, linux-kernel@...r.kernel.org,
rui.zhang@...el.com, amit.daniel@...sung.com,
viresh.kumar@...aro.org, linux-samsung-soc@...r.kernel.org,
yadi.brar01@...il.com
Subject: RE: [PATCH] thermal: cpu_cooling: Update always cpufreq policy with
thermal constraints
Hello Eduardo Valentin,
On Thursday, November 06, 2014 2:17 AM, Eduardo Valentin wrote:
> Hello Yadwinder,
>
> On Wed, Nov 05, 2014 at 05:46:25PM +0530, Yadwinder Singh Brar wrote:
> > Existing code updates cupfreq policy only while executing
> > cpufreq_apply_cooling() function (i.e. when notify_device !=
> NOTIFY_INVALID).
>
> Correct. The case you mention is when we receive a notification from
> cpufreq. But also, updates the cpufreq policy when the cooling device
> changes state, a call from thermal framework.
I mentioned thermal framework case only, existing code updates
cupfreq policy only when (notify_device != NOTIFY_INVALID),
which happens only when notification comes from cpufreq_update_policy
while changing cooling device's state(i.e. cpufreq_apply_cooling()).
In case of other notifications notify_device is always NOTIFY_INVALID.
>
> > It doesn't apply constraints when cpufreq policy update happens from
> > any other place but it should update the cpufreq policy with thermal
> > constraints every time when there is a cpufreq policy update, to keep
> > state of cpufreq_cooling_device and max_feq of cpufreq policy in
> sync.
>
> I am not sure I follow you here. Can you please elaborate on 'any other
> places'? Could you please mention (also in the commit log) what are the
> case the current code does not cover? For instance, the
> cpufreq_apply_cooling gets called on notification coming from thermal
> subsystem, and for changes in cpufreq subsystem,
> cpufreq_thermal_notifier is called.
>
"Other places" mean possible places from where cpufreq_update_policy()
can be called at runtime, an instance in present kernel is cpufreq_resume().
But since cpufreq_update_policy() is an exposed API, I think
for robustness, generic cpu cooling should be able to take care of any
possible case(in future as well).
> >
> > This patch modifies code to maintain a global cpufreq_dev_list and
> get
> > corresponding cpufreq_cooling_device for policy's cpu from
> > cpufreq_dev_list when there is any policy update.
>
> OK. Please give real examples of when the current code fails to catch
> the event.
>
While resuming cpufreq updates cpufreq_policy for boot cpu and it
restores default policy->usr_policy irrespective of cooling device's
cpufreq_state since notification gets missed because (notify_device ==
NOTIFY_INVALID).
Another thing, Rather I would say an issue, I observed is that
Userspace is able to change max_freq irrespective of cooling
device's state, as notification gets missed.
>
> BR,
>
> Eduardo Valentin
>
> >
> > Signed-off-by: Yadwinder Singh Brar <yadi.brar@...sung.com>
> > ---
> > drivers/thermal/cpu_cooling.c | 37 ++++++++++++++++++++-----------
> ------
> > 1 files changed, 20 insertions(+), 17 deletions(-)
> >
> > diff --git a/drivers/thermal/cpu_cooling.c
> > b/drivers/thermal/cpu_cooling.c index 1ab0018..5546278 100644
> > --- a/drivers/thermal/cpu_cooling.c
> > +++ b/drivers/thermal/cpu_cooling.c
> > @@ -50,15 +50,14 @@ struct cpufreq_cooling_device {
> > unsigned int cpufreq_state;
> > unsigned int cpufreq_val;
> > struct cpumask allowed_cpus;
> > + struct list_head node;
> > };
> > static DEFINE_IDR(cpufreq_idr);
> > static DEFINE_MUTEX(cooling_cpufreq_lock);
> >
> > static unsigned int cpufreq_dev_count;
> >
> > -/* notify_table passes value to the CPUFREQ_ADJUST callback
> function.
> > */ -#define NOTIFY_INVALID NULL -static struct cpufreq_cooling_device
> > *notify_device;
> > +static LIST_HEAD(cpufreq_dev_list);
> >
> > /**
> > * get_idr - function to get a unique id.
> > @@ -287,15 +286,12 @@ static int cpufreq_apply_cooling(struct
> > cpufreq_cooling_device *cpufreq_device,
> >
> > cpufreq_device->cpufreq_state = cooling_state;
> > cpufreq_device->cpufreq_val = clip_freq;
> > - notify_device = cpufreq_device;
> >
> > for_each_cpu(cpuid, mask) {
> > if (is_cpufreq_valid(cpuid))
> > cpufreq_update_policy(cpuid);
> > }
> >
> > - notify_device = NOTIFY_INVALID;
> > -
> > return 0;
> > }
> >
> > @@ -316,21 +312,27 @@ static int cpufreq_thermal_notifier(struct
> > notifier_block *nb, {
> > struct cpufreq_policy *policy = data;
> > unsigned long max_freq = 0;
> > + struct cpufreq_cooling_device *cpufreq_dev;
> >
> > - if (event != CPUFREQ_ADJUST || notify_device == NOTIFY_INVALID)
> > + if (event != CPUFREQ_ADJUST)
> > return 0;
> >
> > - if (cpumask_test_cpu(policy->cpu, ¬ify_device->allowed_cpus))
> > - max_freq = notify_device->cpufreq_val;
> > - else
> > - return 0;
> > + mutex_lock(&cooling_cpufreq_lock);
> > + list_for_each_entry(cpufreq_dev, &cpufreq_dev_list, node) {
> > + if (!cpumask_test_cpu(policy->cpu,
> > + &cpufreq_dev->allowed_cpus))
> > + continue;
> >
> > - /* Never exceed user_policy.max */
> > - if (max_freq > policy->user_policy.max)
> > - max_freq = policy->user_policy.max;
> > + max_freq = cpufreq_dev->cpufreq_val;
> >
I think I missed to post updated patch,
Actually it should be :
+ if (!cpufreq_dev->cpufreq_val)
+ cpufreq_dev->cpufreq_val = get_cpu_frequency(
+
cpumask_any(&cpufreq_dev->allowed_cpus),
+ cpufreq_dev->state);
+ max_freq = cpufreq_dev->cpufreq_val;
I will send another version of patch.
> > - if (policy->max != max_freq)
> > - cpufreq_verify_within_limits(policy, 0, max_freq);
> > + /* Never exceed user_policy.max */
> > + if (max_freq > policy->user_policy.max)
> > + max_freq = policy->user_policy.max;
> > +
> > + if (policy->max != max_freq)
> > + cpufreq_verify_within_limits(policy, 0, max_freq);
> > + }
> > + mutex_unlock(&cooling_cpufreq_lock);
>
> So, the problem is when we have several cpu cooling devices and you
> want to search for the real max among the existing cpu cooling devices?
>
Sorry I didn't get your question completely I think.
No, above code doesn't find max among existing cooling devices.
It simply finds cooling device corresponding to policy's cpu
and applies updates policy accordingly.
Regards,
Yadwinder
> > return 0;
> > }
> > @@ -486,7 +488,7 @@ __cpufreq_cooling_register(struct device_node
> *np,
> > cpufreq_register_notifier(&thermal_cpufreq_notifier_block,
> > CPUFREQ_POLICY_NOTIFIER);
> > cpufreq_dev_count++;
> > -
> > + list_add(&cpufreq_dev->node, &cpufreq_dev_list);
> > mutex_unlock(&cooling_cpufreq_lock);
> >
> > return cool_dev;
> > @@ -549,6 +551,7 @@ void cpufreq_cooling_unregister(struct
> > thermal_cooling_device *cdev)
> >
> > cpufreq_dev = cdev->devdata;
> > mutex_lock(&cooling_cpufreq_lock);
> > + list_del(&cpufreq_dev->node);
> > cpufreq_dev_count--;
> >
> > /* Unregister the notifier for the last cpufreq cooling device */
> > --
> > 1.7.0.4
> >
--
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