Re: [linux-pm] [RFC PATCH 2/5] thermal: cpu_cooling: Add notifications support for the clients

[amit daniel kachhap]

On Fri, May 16, 2014 at 12:15 AM, Eduardo Valentin <edubezval@xxxxxxxxx> wrote:
> Hello Amit,
>
>
> On Thu, May 08, 2014 at 08:07:57PM +0530, Amit Daniel Kachhap wrote:
>> This patch adds notification support for those clients of cpu_cooling
>> APIs which may want to do something interesting after receiving these
>> cpu_cooling events. The notifier structure passed is of both Set/Get type.
>> The notfications events can be of type,
>> 1. CPU_COOLING_SET_STATE_PRE
>> 2. CPU_COOLING_SET_STATE_POST
>> 3. CPU_COOLING_GET_CUR_STATE
>> 4. CPU_COOLING_GET_MAX_STATE
>
> What do you think about expanding this feature to all cooling devices?
>
> I mean, why should we restrict to cpu(freq) cooling?
nice suggestion. Sure will check its feasibility.
>
> The clock cooling device I posted (and that I plan to merge soon) should
> also benefit of this infrastructure. The clock cooling is for the
> context of other processing units, that do not benefit of cpufreq.
ok let me check them.
>
>
>>
>> The advantages of these notfications is to differentiate between different
>> P states in the cpufreq table and the cooling states. The clients of these
>> events may group few P states into 1 cooling states. Also some more cooling
>> states can be enabled when the maximum of P state is reached. Post notifications
>> can be used for those cases.
>>
>> Signed-off-by: Amit Daniel Kachhap <amit.daniel@xxxxxxxxxxx>
>> ---
>>  drivers/thermal/cpu_cooling.c |   99 +++++++++++++++++++++++++++++++++++++++-
>>  include/linux/cpu_cooling.h   |   55 +++++++++++++++++++++++
>>  2 files changed, 151 insertions(+), 3 deletions(-)
>>
>> diff --git a/drivers/thermal/cpu_cooling.c b/drivers/thermal/cpu_cooling.c
>> index 21f44d4..e2aeb36 100644
>> --- a/drivers/thermal/cpu_cooling.c
>> +++ b/drivers/thermal/cpu_cooling.c
>> @@ -50,6 +50,7 @@ struct cpufreq_cooling_device {
>>       unsigned int cpufreq_state;
>>       unsigned int cpufreq_val;
>>       struct cpumask allowed_cpus;
>> +     struct cpufreq_cooling_status request_status;
>>       struct list_head node;
>>  };
>>  static DEFINE_IDR(cpufreq_idr);
>> @@ -59,6 +60,8 @@ static DEFINE_MUTEX(cooling_cpufreq_lock);
>>  #define NOTIFY_INVALID NULL
>>  static struct cpufreq_cooling_device *notify_device;
>>
>> +/* Notfier list to validates/updates the cpufreq cooling states */
>> +static BLOCKING_NOTIFIER_HEAD(cpufreq_cooling_state_notifier_list);
>>  /* A list to hold all the cpufreq cooling devices registered */
>>  static LIST_HEAD(cpufreq_cooling_list);
>>
>> @@ -266,6 +269,21 @@ static unsigned int get_cpu_frequency(unsigned int cpu, unsigned long level)
>>       return freq;
>>  }
>>
>> +static int
>> +cpufreq_cooling_notify_states(struct cpufreq_cooling_status *request,
>> +                     enum cpu_cooling_state_ops op)
>> +{
>> +     /* Invoke the notifiers which have registered for this state change */
>> +     if (op == CPU_COOLING_SET_STATE_PRE ||
>> +             op == CPU_COOLING_SET_STATE_POST ||
>> +             op == CPU_COOLING_GET_MAX_STATE ||
>> +             op == CPU_COOLING_GET_CUR_STATE) {
>> +             blocking_notifier_call_chain(
>> +                     &cpufreq_cooling_state_notifier_list, op, request);
>> +     }
>> +     return 0;
>> +}
>> +
>>  /**
>>   * cpufreq_apply_cooling - function to apply frequency clipping.
>>   * @cpufreq_device: cpufreq_cooling_device pointer containing frequency
>> @@ -285,9 +303,18 @@ static int cpufreq_apply_cooling(struct cpufreq_cooling_device *cpufreq_device,
>>       struct cpumask *mask = &cpufreq_device->allowed_cpus;
>>       unsigned int cpu = cpumask_any(mask);
>>
>> +     cpufreq_device->request_status.cur_state =
>> +                                             cpufreq_device->cpufreq_state;
>> +     cpufreq_device->request_status.new_state = cooling_state;
>> +
>> +     cpufreq_cooling_notify_states(&cpufreq_device->request_status,
>> +                                     CPU_COOLING_SET_STATE_PRE);
>> +
>
> Can a listener block/abort/postpone a state transition?
>
>> +     cooling_state = cpufreq_device->request_status.new_state;
>>
>
> So you are proposing listeners can have control on target cpufreq state,
> right? Or did I get it wrong?
>
> I think we should have this better documented. Besides, if that is the
> case, what happens if we have several listeners?
>
>>       /* Check if the old cooling action is same as new cooling action */
>> -     if (cpufreq_device->cpufreq_state == cooling_state)
>> +     if (cpufreq_device->cpufreq_state ==
>> +                             cpufreq_device->request_status.new_state)
>>               return 0;
>>
>>       clip_freq = get_cpu_frequency(cpu, cooling_state);
>> @@ -304,7 +331,8 @@ static int cpufreq_apply_cooling(struct cpufreq_cooling_device *cpufreq_device,
>>       }
>>
>>       notify_device = NOTIFY_INVALID;
>> -
>> +     cpufreq_cooling_notify_states(&cpufreq_device->request_status,
>> +                                     CPU_COOLING_SET_STATE_POST);
>>       return 0;
>>  }
>>
>> @@ -383,6 +411,11 @@ static int cpufreq_get_max_state(struct thermal_cooling_device *cdev,
>>       if (count > 0)
>>               *state = count;
>>
>> +     cpufreq_device->request_status.max_state = count;
>> +     cpufreq_cooling_notify_states(&cpufreq_device->request_status,
>> +                                     CPU_COOLING_GET_MAX_STATE);
>> +     *state = cpufreq_device->request_status.max_state;
>> +
>
> same question here, who determines the priorities when several listeners
> are present in the system?
>
>>       return ret;
>>  }
>>
>> @@ -410,8 +443,12 @@ static int cpufreq_get_cur_state(struct thermal_cooling_device *cdev,
>>               /* Cooling device pointer not found */
>>               return -EINVAL;
>>       }
>> +     cpufreq_device->request_status.cur_state =
>> +                                             cpufreq_device->cpufreq_state;
>> +     cpufreq_cooling_notify_states(&cpufreq_device->request_status,
>> +                                     CPU_COOLING_GET_CUR_STATE);
>>
>
> ditto.
>
>> -     *state = cpufreq_device->cpufreq_state;
>> +     *state = cpufreq_device->request_status.cur_state;
>>
>>       return 0;
>>  }
>> @@ -520,6 +557,7 @@ __cpufreq_cooling_register(struct device_node *np,
>>       }
>>       cpufreq_dev->cool_dev = cool_dev;
>>       cpufreq_dev->cpufreq_state = 0;
>> +     cpufreq_dev->request_status.devdata = devdata;
>>       mutex_lock(&cooling_cpufreq_lock);
>>
>>       /* Register the notifier for first cpufreq cooling device */
>> @@ -614,3 +652,58 @@ void cpufreq_cooling_unregister(struct thermal_cooling_device *cdev)
>>       kfree(cpufreq_dev);
>>  }
>>  EXPORT_SYMBOL_GPL(cpufreq_cooling_unregister);
>> +
>> +/**
>> + * cpufreq_cooling_register_notifier - register a driver with cpufreq cooling.
>> + * @nb:      notifier function to register.
>> + * @list: CPU_COOLING_STATE_NOTIFIER type.
>> + *
>> + * Add a driver to receive cpufreq cooling notifications like current state,
>> + * max state and set state. The drivers after reading the events can perform
>> + * some mapping between the P states and cooling states like grouping some P
>> + * states into 1 cooling state.
>> + *
>> + * Return: 0 (success)
>> + */
>> +int cpufreq_cooling_register_notifier(struct notifier_block *nb,
>> +                                     unsigned int list)
>> +{
>> +     int ret = 0;
>> +     switch (list) {
>> +     case CPU_COOLING_STATE_NOTIFIER:
>> +             ret = blocking_notifier_chain_register(
>> +                             &cpufreq_cooling_state_notifier_list, nb);
>> +             break;
>> +     default:
>> +             ret = -EINVAL;
>> +     }
>> +     return ret;
>> +}
>> +EXPORT_SYMBOL_GPL(cpufreq_cooling_register_notifier);
>> +
>> +/**
>> + * cpufreq_cooling_unregister_notifier - unregisters a driver with cpufreq
>> + * cooling.
>> + * @nb:      notifier function to unregister.
>> + * @list: CPU_COOLING_STATE_NOTIFIER type.
>> + *
>> + * Removes a driver to receive further cpufreq cooling notifications.
>> + *
>> + * Return: 0 (success)
>> + */
>> +int cpufreq_cooling_unregister_notifier(struct notifier_block *nb,
>> +                                     unsigned int list)
>> +{
>> +     int ret = 0;
>> +     switch (list) {
>> +     case CPU_COOLING_STATE_NOTIFIER:
>> +             ret = blocking_notifier_chain_unregister(
>> +                             &cpufreq_cooling_state_notifier_list, nb);
>> +             break;
>> +     default:
>> +             ret = -EINVAL;
>> +     }
>> +
>> +     return ret;
>> +}
>> +EXPORT_SYMBOL_GPL(cpufreq_cooling_unregister_notifier);
>
> The exported symbols must be documented under Documentation/ too.
>
>> diff --git a/include/linux/cpu_cooling.h b/include/linux/cpu_cooling.h
>> index aaef7d8..f786935 100644
>> --- a/include/linux/cpu_cooling.h
>> +++ b/include/linux/cpu_cooling.h
>> @@ -28,6 +28,22 @@
>>  #include <linux/thermal.h>
>>  #include <linux/cpumask.h>
>>
>> +#define CPU_COOLING_STATE_NOTIFIER   (0)
>> +
>> +enum cpu_cooling_state_ops {
>> +     CPU_COOLING_SET_STATE_PRE,
>> +     CPU_COOLING_SET_STATE_POST,
>> +     CPU_COOLING_GET_CUR_STATE,
>> +     CPU_COOLING_GET_MAX_STATE,
>> +};
>> +
>> +struct cpufreq_cooling_status {
>> +     unsigned long cur_state;
>> +     unsigned long new_state;
>> +     unsigned long max_state;
>> +     void *devdata;
>> +};
>> +
>>  #ifdef CONFIG_CPU_THERMAL
>>  /**
>>   * cpufreq_cooling_register - function to create cpufreq cooling device.
>> @@ -62,6 +78,34 @@ of_cpufreq_cooling_register(struct device_node *np,
>>  void cpufreq_cooling_unregister(struct thermal_cooling_device *cdev);
>>
>>  unsigned long cpufreq_cooling_get_level(unsigned int cpu, unsigned int freq);
>> +
>> +/**
>> + * cpufreq_cooling_register_notifier - register a driver with cpufreq cooling.
>> + * @nb:      notifier function to register.
>> + * @list: CPU_COOLING_STATE_NOTIFIER type.
>> + *
>> + * Add a driver to receive cpufreq cooling notifications like current state,
>> + * max state and set state. The drivers after reading the events can perform
>> + * some mapping between the P states and cooling states like grouping some P
>> + * states into 1 cooling state.
>> + *
>> + * Return: 0 (success)
>> + */
>> +int cpufreq_cooling_register_notifier(struct notifier_block *nb,
>> +                                     unsigned int list);
>> +
>> +/**
>> + * cpufreq_cooling_unregister_notifier - unregisters a driver with cpufreq
>> + * cooling.
>> + * @nb:      notifier function to unregister.
>> + * @list: CPU_COOLING_STATE_NOTIFIER type.
>> + *
>> + * Removes a driver to receive further cpufreq cooling notifications.
>> + *
>> + * Return: 0 (success)
>> + */
>> +int cpufreq_cooling_unregister_notifier(struct notifier_block *nb,
>> +                                     unsigned int list);
>>  #else /* !CONFIG_CPU_THERMAL */
>>  static inline struct thermal_cooling_device *
>>  cpufreq_cooling_register(const struct cpumask *clip_cpus, void *devdata)
>> @@ -84,6 +128,17 @@ unsigned long cpufreq_cooling_get_level(unsigned int cpu, unsigned int freq)
>>  {
>>       return THERMAL_CSTATE_INVALID;
>>  }
>> +static inline int
>> +cpufreq_cooling_register_notifier(struct notifier_block *nb, unsigned int list)
>> +{
>> +     return 0;
>> +}
>> +static inline int
>> +cpufreq_cooling_unregister_notifier(struct notifier_block *nb,
>> +                                     unsigned int list)
>> +{
>> +     return 0;
>> +}
>>  #endif       /* CONFIG_CPU_THERMAL */
>>
>>  #endif /* __CPU_COOLING_H__ */
>> --
>> 1.7.1
>>
>> --
>> To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
>> the body of a message to majordomo@xxxxxxxxxxxxxxx
>> More majordomo info at  http://vger.kernel.org/majordomo-info.html
>> Please read the FAQ at  http://www.tux.org/lkml/
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/