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Message-ID: <7fe76a95-fe92-386d-7ff7-4c2a0b478724@linaro.org>
Date: Tue, 22 Dec 2020 18:05:40 +0100
From: Daniel Lezcano <daniel.lezcano@...aro.org>
To: rui.zhang@...el.com
Cc: mjg59@...on.org.uk, linux-pm@...r.kernel.org,
linux-kernel@...r.kernel.org, amitk@...nel.org,
thara.gopinath@...aro.org, Jonathan Corbet <corbet@....net>,
Viresh Kumar <viresh.kumar@...aro.org>,
"open list:DOCUMENTATION" <linux-doc@...r.kernel.org>
Subject: Re: [PATCH 1/6] thermal/core: Remove the 'forced_passive' option
On 15/12/2020 00:38, Daniel Lezcano wrote:
> The code was reorganized in 2012 with the commit 0c01ebbfd3caf1.
>
> The main change is a loop on the trip points array and a unconditional
> call to the throttle() ops of the governors for each of them even if
> the trip temperature is not reached yet.
>
> With this change, the 'forced_passive' is no longer checked in the
> thermal_zone_device_update() function but in the step wise governor's
> throttle() callback.
>
> As the force_passive does no belong to the trip point array, the
> thermal_zone_device_update() can not compare with the specified
> passive temperature, thus does not detect the passive limit has been
> crossed. Consequently, throttle() is never called and the
> 'forced_passive' branch is unreached.
>
> In addition, the default processor cooling device is not automatically
> bound to the thermal zone if there is not passive trip point, thus the
> 'forced_passive' can not operate.
>
> If there is an active trip point, then the throttle function will be
> called to mitigate at this temperature and the 'forced_passive' will
> override the mitigation of the active trip point in this case but with
> the default cooling device bound to the thermal zone, so usually a
> fan, and that is not a passive cooling effect.
>
> Given the regression exists since more than 8 years, nobody complained
> and at the best of my knowledge there is no bug open in
> https://bugzilla.kernel.org, it is reasonable to say it is unused.
>
> Remove the 'forced_passive' related code.
>
> Signed-off-by: Daniel Lezcano <daniel.lezcano@...aro.org>
Is there any concern with this series ?
> ---
> .../driver-api/thermal/sysfs-api.rst | 13 ---
> drivers/thermal/gov_step_wise.c | 14 +---
> drivers/thermal/thermal_sysfs.c | 80 -------------------
> include/linux/thermal.h | 4 -
> 4 files changed, 3 insertions(+), 108 deletions(-)
>
> diff --git a/Documentation/driver-api/thermal/sysfs-api.rst b/Documentation/driver-api/thermal/sysfs-api.rst
> index e7520cb439ac..a4969c474cc3 100644
> --- a/Documentation/driver-api/thermal/sysfs-api.rst
> +++ b/Documentation/driver-api/thermal/sysfs-api.rst
> @@ -520,19 +520,6 @@ available_policies
>
> RW, Optional
>
> -passive
> - Attribute is only present for zones in which the passive cooling
> - policy is not supported by native thermal driver. Default is zero
> - and can be set to a temperature (in millidegrees) to enable a
> - passive trip point for the zone. Activation is done by polling with
> - an interval of 1 second.
> -
> - Unit: millidegrees Celsius
> -
> - Valid values: 0 (disabled) or greater than 1000
> -
> - RW, Optional
> -
> emul_temp
> Interface to set the emulated temperature method in thermal zone
> (sensor). After setting this temperature, the thermal zone may pass
> diff --git a/drivers/thermal/gov_step_wise.c b/drivers/thermal/gov_step_wise.c
> index 2ae7198d3067..12acb12aac50 100644
> --- a/drivers/thermal/gov_step_wise.c
> +++ b/drivers/thermal/gov_step_wise.c
> @@ -109,7 +109,7 @@ static void update_passive_instance(struct thermal_zone_device *tz,
> * If value is +1, activate a passive instance.
> * If value is -1, deactivate a passive instance.
> */
> - if (type == THERMAL_TRIP_PASSIVE || type == THERMAL_TRIPS_NONE)
> + if (type == THERMAL_TRIP_PASSIVE)
> tz->passive += value;
> }
>
> @@ -122,13 +122,8 @@ static void thermal_zone_trip_update(struct thermal_zone_device *tz, int trip)
> bool throttle = false;
> int old_target;
>
> - if (trip == THERMAL_TRIPS_NONE) {
> - trip_temp = tz->forced_passive;
> - trip_type = THERMAL_TRIPS_NONE;
> - } else {
> - tz->ops->get_trip_temp(tz, trip, &trip_temp);
> - tz->ops->get_trip_type(tz, trip, &trip_type);
> - }
> + tz->ops->get_trip_temp(tz, trip, &trip_temp);
> + tz->ops->get_trip_type(tz, trip, &trip_type);
>
> trend = get_tz_trend(tz, trip);
>
> @@ -189,9 +184,6 @@ static int step_wise_throttle(struct thermal_zone_device *tz, int trip)
>
> thermal_zone_trip_update(tz, trip);
>
> - if (tz->forced_passive)
> - thermal_zone_trip_update(tz, THERMAL_TRIPS_NONE);
> -
> mutex_lock(&tz->lock);
>
> list_for_each_entry(instance, &tz->thermal_instances, tz_node)
> diff --git a/drivers/thermal/thermal_sysfs.c b/drivers/thermal/thermal_sysfs.c
> index 0866e949339b..4e7f9e880d76 100644
> --- a/drivers/thermal/thermal_sysfs.c
> +++ b/drivers/thermal/thermal_sysfs.c
> @@ -216,49 +216,6 @@ trip_point_hyst_show(struct device *dev, struct device_attribute *attr,
> return ret ? ret : sprintf(buf, "%d\n", temperature);
> }
>
> -static ssize_t
> -passive_store(struct device *dev, struct device_attribute *attr,
> - const char *buf, size_t count)
> -{
> - struct thermal_zone_device *tz = to_thermal_zone(dev);
> - int state;
> -
> - if (sscanf(buf, "%d\n", &state) != 1)
> - return -EINVAL;
> -
> - /* sanity check: values below 1000 millicelcius don't make sense
> - * and can cause the system to go into a thermal heart attack
> - */
> - if (state && state < 1000)
> - return -EINVAL;
> -
> - if (state && !tz->forced_passive) {
> - if (!tz->passive_delay)
> - tz->passive_delay = 1000;
> - thermal_zone_device_rebind_exception(tz, "Processor",
> - sizeof("Processor"));
> - } else if (!state && tz->forced_passive) {
> - tz->passive_delay = 0;
> - thermal_zone_device_unbind_exception(tz, "Processor",
> - sizeof("Processor"));
> - }
> -
> - tz->forced_passive = state;
> -
> - thermal_zone_device_update(tz, THERMAL_EVENT_UNSPECIFIED);
> -
> - return count;
> -}
> -
> -static ssize_t
> -passive_show(struct device *dev, struct device_attribute *attr,
> - char *buf)
> -{
> - struct thermal_zone_device *tz = to_thermal_zone(dev);
> -
> - return sprintf(buf, "%d\n", tz->forced_passive);
> -}
> -
> static ssize_t
> policy_store(struct device *dev, struct device_attribute *attr,
> const char *buf, size_t count)
> @@ -403,7 +360,6 @@ static DEVICE_ATTR_RW(sustainable_power);
>
> /* These thermal zone device attributes are created based on conditions */
> static DEVICE_ATTR_RW(mode);
> -static DEVICE_ATTR_RW(passive);
>
> /* These attributes are unconditionally added to a thermal zone */
> static struct attribute *thermal_zone_dev_attrs[] = {
> @@ -438,45 +394,9 @@ static const struct attribute_group thermal_zone_mode_attribute_group = {
> .attrs = thermal_zone_mode_attrs,
> };
>
> -/* We expose passive only if passive trips are present */
> -static struct attribute *thermal_zone_passive_attrs[] = {
> - &dev_attr_passive.attr,
> - NULL,
> -};
> -
> -static umode_t thermal_zone_passive_is_visible(struct kobject *kobj,
> - struct attribute *attr,
> - int attrno)
> -{
> - struct device *dev = kobj_to_dev(kobj);
> - struct thermal_zone_device *tz;
> - enum thermal_trip_type trip_type;
> - int count, passive = 0;
> -
> - tz = container_of(dev, struct thermal_zone_device, device);
> -
> - for (count = 0; count < tz->trips && !passive; count++) {
> - tz->ops->get_trip_type(tz, count, &trip_type);
> -
> - if (trip_type == THERMAL_TRIP_PASSIVE)
> - passive = 1;
> - }
> -
> - if (!passive)
> - return attr->mode;
> -
> - return 0;
> -}
> -
> -static const struct attribute_group thermal_zone_passive_attribute_group = {
> - .attrs = thermal_zone_passive_attrs,
> - .is_visible = thermal_zone_passive_is_visible,
> -};
> -
> static const struct attribute_group *thermal_zone_attribute_groups[] = {
> &thermal_zone_attribute_group,
> &thermal_zone_mode_attribute_group,
> - &thermal_zone_passive_attribute_group,
> /* This is not NULL terminated as we create the group dynamically */
> };
>
> diff --git a/include/linux/thermal.h b/include/linux/thermal.h
> index c80032322158..a57232a9a6f9 100644
> --- a/include/linux/thermal.h
> +++ b/include/linux/thermal.h
> @@ -131,9 +131,6 @@ struct thermal_cooling_device {
> trip point.
> * @prev_high_trip: the above current temperature if you've crossed a
> passive trip point.
> - * @forced_passive: If > 0, temperature at which to switch on all ACPI
> - * processor cooling devices. Currently only used by the
> - * step-wise governor.
> * @need_update: if equals 1, thermal_zone_device_update needs to be invoked.
> * @ops: operations this &thermal_zone_device supports
> * @tzp: thermal zone parameters
> @@ -167,7 +164,6 @@ struct thermal_zone_device {
> int passive;
> int prev_low_trip;
> int prev_high_trip;
> - unsigned int forced_passive;
> atomic_t need_update;
> struct thermal_zone_device_ops *ops;
> struct thermal_zone_params *tzp;
>
--
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