Re: [PATCH v2 1/4] thermal: power_allocator: relax the requirement of a sustainable_power in tzp

Punit Agrawal
2015-08-11T13:41:10Z

Hi Javi,

A few nitpicks and a comment below.

Javi Merino <javi.merino@arm.com> writes:

> The power allocator governor currently requires that a sustainable power
> is passed as part of the thermal zone's thermal zone parameters. If
> that parameter is not provided, it doesn't register with the thermal
> zone.
>
> While this parameter is strongly recommended for optimal performance, it
> doesn't need to be mandatory. Relax the requirement and allow the
> governor to bind to thermal zones that don't provide it by estimating it
> from the cooling devices' power model.
>
> Cc: Zhang Rui <rui.zhang@intel.com>
> Cc: Eduardo Valentin <edubezval@gmail.com>
> Signed-off-by: Javi Merino <javi.merino@arm.com>
> ---
> drivers/thermal/power_allocator.c | 62 +++++++++++++++++++++++++++++++++------
> drivers/thermal/thermal_core.c | 28 ++++++++++++++++++
> include/linux/thermal.h | 6 ++++
> 3 files changed, 87 insertions(+), 9 deletions(-)
>
> diff --git a/drivers/thermal/power_allocator.c b/drivers/thermal/power_allocator.c
> index 63a448f9d93b..f78836c2da26 100644
> --- a/drivers/thermal/power_allocator.c
> +++ b/drivers/thermal/power_allocator.c
> @@ -73,6 +73,39 @@ struct power_allocator_params {
> };
>
> /**
> + * estimate_sustainable_power() - Estimate the sustainable power of a thermal zone
> + * @tz: thermal zone we are operating in
> + *
> + * For thermal zones that don't provide a sustainable_power in their
> + * thermal_zone_params, estimate one. Calculate it using the minimum
> + * power of all the cooling devices as that gives a valid value that
> + * can give some degree of functionality. For optimal performance of
> + * this governor, provide a sustainable_power in the thermal zone's
> + * thermal_zone_params.
> + */
> +static u32 estimate_sustainable_power(struct thermal_zone_device *tz)
> +{
> + u32 sustainable_power = 0;
> + struct thermal_instance *instance;
> + struct power_allocator_params *params = tz->governor_data;
> +
> + list_for_each_entry(instance, &tz->thermal_instances, tz_node) {
> + struct thermal_cooling_device *cdev = instance->cdev;
> + u32 min_power;
> +
> + if (instance->trip != params->trip_max_desired_temperature)
> + continue;
> +
> + if (power_actor_get_min_power(cdev, tz, &min_power))
> + continue;
> +
> + sustainable_power += min_power;
> + }
> +
> + return sustainable_power;
> +}
> +
> +/**
> * pid_controller() - PID controller
> * @tz: thermal zone we are operating in
> * @current_temp: the current temperature in millicelsius
> @@ -98,6 +131,7 @@ static u32 pid_controller(struct thermal_zone_device *tz,
> {
> s64 p, i, d, power_range;
> s32 err, max_power_frac;
> + u32 sustainable_power;
> struct power_allocator_params *params = tz->governor_data;
>
> max_power_frac = int_to_frac(max_allocatable_power);
> @@ -138,8 +172,11 @@ static u32 pid_controller(struct thermal_zone_device *tz,
>
> power_range = p + i + d;
>
> + sustainable_power = tz->tzp->sustainable_power ?:
> + estimate_sustainable_power(tz);
> +
> /* feed-forward the known sustainable dissipatable power */
> - power_range = tz->tzp->sustainable_power + frac_to_int(power_range);
> + power_range = sustainable_power + frac_to_int(power_range);
>
> power_range = clamp(power_range, (s64)0, (s64)max_allocatable_power);
>
> @@ -418,18 +455,18 @@ static int power_allocator_bind(struct thermal_zone_device *tz)
> int ret;
> struct power_allocator_params *params;
> unsigned long switch_on_temp, control_temp;
> - u32 temperature_threshold;
> + u32 sustainable_power, temperature_threshold;
>
> - if (!tz->tzp || !tz->tzp->sustainable_power) {
> - dev_err(&tz->device,
> - "power_allocator: missing sustainable_power\n");
> + if (!tz->tzp)
> return -EINVAL;
> - }
>
> params = devm_kzalloc(&tz->device, sizeof(*params), GFP_KERNEL);
> if (!params)
> return -ENOMEM;
>
> + if (!tz->tzp->sustainable_power)
> + dev_warn(&tz->device, "power_allocator: sustainable_power will be estimated\n");
> +
> ret = get_governor_trips(tz, params);
> if (ret) {
> dev_err(&tz->device,
> @@ -448,13 +485,20 @@ static int power_allocator_bind(struct thermal_zone_device *tz)
> if (ret)
> goto free;
>
> + /*
> + * Provide an arbitrary sustainable_power to set the default
> + * values of k_po and k_pu. We can estimate sustainable_power
^
can not
> + * at this point because no cooling devices have been
> + * registered yet. By providing an arbitrary value we get
> + * better defaults that setting k_po and k_pu to 0.
^
than

> + */
> + sustainable_power = tz->tzp->sustainable_power ?: 2500;
> temperature_threshold = control_temp - switch_on_temp;
>
> tz->tzp->k_po = tz->tzp->k_po ?:
> - int_to_frac(tz->tzp->sustainable_power) / temperature_threshold;
> + int_to_frac(sustainable_power) / temperature_threshold;
> tz->tzp->k_pu = tz->tzp->k_pu ?:
> - int_to_frac(2 * tz->tzp->sustainable_power) /
> - temperature_threshold;
> + int_to_frac(2 * sustainable_power) / temperature_threshold;

As we are being conservative with our estimation of sustainable power
(sum of mins) when it is not explicitly specified, should we be
conservative here and let the proportional terms, k_po and k_pu be zero
as well?

> tz->tzp->k_i = tz->tzp->k_i ?: int_to_frac(10) / 1000;
> /*
> * The default for k_d and integral_cutoff is 0, so we can
> diff --git a/drivers/thermal/thermal_core.c b/drivers/thermal/thermal_core.c
> index 4ca211be4c0f..d26bc9e6f936 100644
> --- a/drivers/thermal/thermal_core.c
> +++ b/drivers/thermal/thermal_core.c
> @@ -997,6 +997,34 @@ int power_actor_get_max_power(struct thermal_cooling_device *cdev,
> }
>
> /**
> + * power_actor_get_min_power() - get the mainimum power that a cdev can consume
> + * @cdev: pointer to &thermal_cooling_device
> + * @tz: a valid thermal zone device pointer
> + * @min_power: pointer in which to store the minimum power
> + *
> + * Calculate the minimum power consumption in milliwats that the
> + * cooling device can currently consume and store it in @min_power.
> + *
> + * Return: 0 on success, -EINVAL if @cdev doesn't support the
> + * power_actor API or -E* on other error.
> + */
> +int power_actor_get_min_power(struct thermal_cooling_device *cdev,
> + struct thermal_zone_device *tz, u32 *min_power)
> +{
> + unsigned long max_state;
> + int ret;
> +
> + if (!cdev_is_power_actor(cdev))
> + return -EINVAL;
> +
> + ret = cdev->ops->get_max_state(cdev, &max_state);
> + if (ret)
> + return ret;
> +
> + return cdev->ops->state2power(cdev, tz, max_state, min_power);
> +}
> +
> +/**
> * power_actor_set_power() - limit the maximum power that a cooling device can consume
> * @cdev: pointer to &thermal_cooling_device
> * @instance: thermal instance to update
> diff --git a/include/linux/thermal.h b/include/linux/thermal.h
> index 037e9df2f610..f99d934d373a 100644
> --- a/include/linux/thermal.h
> +++ b/include/linux/thermal.h
> @@ -384,6 +384,8 @@ static inline bool cdev_is_power_actor(struct thermal_cooling_device *cdev)
>
> int power_actor_get_max_power(struct thermal_cooling_device *,
> struct thermal_zone_device *tz, u32 *max_power);
> +int power_actor_get_min_power(struct thermal_cooling_device *,
> + struct thermal_zone_device *tz, u32 *min_power);
> int power_actor_set_power(struct thermal_cooling_device *,
> struct thermal_instance *, u32);
> struct thermal_zone_device *thermal_zone_device_register(const char *, int, int,
> @@ -419,6 +421,10 @@ static inline bool cdev_is_power_actor(struct thermal_cooling_device *cdev)
> static inline int power_actor_get_max_power(struct thermal_cooling_device *cdev,
> struct thermal_zone_device *tz, u32 *max_power)
> { return 0; }
> +static inline int power_actor_get_min_power(struct thermal_cooling_device *cdev,
> + struct thermal_zone_device *tz,
> + u32 *min_power)
> +{ return -ENODEV; }

Perhaps return 0 like power_actor_get_max_power just above for
consistency.

> static inline int power_actor_set_power(struct thermal_cooling_device *cdev,
> struct thermal_instance *tz, u32 power)
> { return 0; }