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SubjectRe: [linux-pm] [PATCH 1/4] thermal: Add a new trip type to use cooling device instance number
From
Hi Eduardo,

On 3 April 2012 19:45, Eduardo Valentin <eduardo.valentin@ti.com> wrote:
> Hello,
>
> On Thu, Feb 23, 2012 at 04:50:14PM +0530, Amit Kachhap wrote:
>> On 23 February 2012 12:16, R, Durgadoss <durgadoss.r@intel.com> wrote:
>> > Hi Amit,
>> >
>> >> -----Original Message-----
>> >> From: amit kachhap [mailto:amitdanielk@gmail.com] On Behalf Of Amit Daniel
>> >> Kachhap
>> >> Sent: Wednesday, February 22, 2012 3:44 PM
>> >> To: linux-pm@lists.linux-foundation.org
>> >> Cc: linux-kernel@vger.kernel.org; mjg59@srcf.ucam.org; linux-
>> >> acpi@vger.kernel.org; lenb@kernel.org; linaro-dev@lists.linaro.org;
>> >> amit.kachhap@linaro.org; R, Durgadoss; rob.lee@linaro.org; patches@linaro.org
>> >> Subject: [PATCH 1/4] thermal: Add a new trip type to use cooling device
>> >> instance number
>> >>
>> >> This patch adds a new trip type THERMAL_TRIP_STATE_ACTIVE. This
>> >> trip behaves same as THERMAL_TRIP_ACTIVE but also passes the cooling
>> >> device instance number. This helps the cooling device registered as
>> >> different instances to perform appropriate cooling action decision in
>> >> the set_cur_state call back function.
>> >>
>> >> Also since the trip temperature's are in ascending order so some logic
>> >> is put in place to skip the un-necessary checks.
>> >>
>> >> Signed-off-by: Amit Daniel Kachhap <amit.kachhap@linaro.org>
>> >> ---
>> >>  Documentation/thermal/sysfs-api.txt |    4 +-
>> >>  drivers/thermal/thermal_sys.c       |   45 ++++++++++++++++++++++++++++++++--
>> >>  include/linux/thermal.h             |    1 +
>> >>  3 files changed, 45 insertions(+), 5 deletions(-)
>> >>
>> >> diff --git a/Documentation/thermal/sysfs-api.txt b/Documentation/thermal/sysfs-
>> >> api.txt
>> >> index 1733ab9..7a0c080 100644
>> >> --- a/Documentation/thermal/sysfs-api.txt
>> >> +++ b/Documentation/thermal/sysfs-api.txt
>> >> @@ -184,8 +184,8 @@ trip_point_[0-*]_temp
>> >>
>> >>  trip_point_[0-*]_type
>> >>       Strings which indicate the type of the trip point.
>> >> -     E.g. it can be one of critical, hot, passive, active[0-*] for ACPI
>> >> -     thermal zone.
>> >> +     E.g. it can be one of critical, hot, passive, active[0-1],
>> >> +     state-active[0-*] for ACPI thermal zone.
>> >>       RO, Optional
>> >>
>> >>  cdev[0-*]
>> >> diff --git a/drivers/thermal/thermal_sys.c b/drivers/thermal/thermal_sys.c
>> >> index 220ce7e..d4c9b20 100644
>> >> --- a/drivers/thermal/thermal_sys.c
>> >> +++ b/drivers/thermal/thermal_sys.c
>> >> @@ -192,6 +192,8 @@ trip_point_type_show(struct device *dev, struct
>> >> device_attribute *attr,
>> >>               return sprintf(buf, "passive\n");
>> >>       case THERMAL_TRIP_ACTIVE:
>> >>               return sprintf(buf, "active\n");
>> >> +     case THERMAL_TRIP_STATE_ACTIVE:
>> >> +             return sprintf(buf, "state-active\n");
>> >>       default:
>> >>               return sprintf(buf, "unknown\n");
>> >>       }
>> >> @@ -1034,10 +1036,10 @@ EXPORT_SYMBOL(thermal_cooling_device_unregister);
>> >>
>> >>  void thermal_zone_device_update(struct thermal_zone_device *tz)
>> >>  {
>> >> -     int count, ret = 0;
>> >> -     long temp, trip_temp;
>> >> +     int count, ret = 0, inst_id;
>> >> +     long temp, trip_temp, max_state, last_trip_change = 0;
>> >>       enum thermal_trip_type trip_type;
>> >> -     struct thermal_cooling_device_instance *instance;
>> >> +     struct thermal_cooling_device_instance *instance, *state_instance;
>> >>       struct thermal_cooling_device *cdev;
>> >>
>> >>       mutex_lock(&tz->lock);
>> >> @@ -1086,6 +1088,43 @@ void thermal_zone_device_update(struct
>> >> thermal_zone_device *tz)
>> >>                                       cdev->ops->set_cur_state(cdev, 0);
>> >>                       }
>> >>                       break;
>> >> +             case THERMAL_TRIP_STATE_ACTIVE:
>> >> +                     list_for_each_entry(instance, &tz->cooling_devices,
>> >> +                                         node) {
>> >> +                             if (instance->trip != count)
>> >> +                                     continue;
>> >> +
>> >> +                             if (temp <= last_trip_change)
>> >> +                                     continue;
>> >> +
>> >> +                             inst_id = 0;
>> >> +                             /*
>> >> +                             *For this instance how many instance of same
>> >> +                             *cooling device occured before
>> >> +                             */
>> >> +
>> >> +                             list_for_each_entry(state_instance,
>> >> +                                             &tz->cooling_devices, node) {
>> >> +                                     if (instance->cdev ==
>> >> +                                                     state_instance->cdev)
>> >> +                                             inst_id++;
>> >> +                                     if (state_instance->trip == count)
>> >> +                                             break;
>> >> +                             }
>> >
>> > Can you explain a bit more on this loop and the set_cur_state below ?
>> > Sorry, I don't get the logic behind this..
>>
>> This loop is basically finding the instance id of the same cooling device.
>> Say we have done like this,
>> thermal_zone_bind_cooling_device(thermal, 2, cdev);
>> thermal_zone_bind_cooling_device(thermal, 3, cdev);
>> thermal_zone_bind_cooling_device(thermal, 4, cdev);
>>
>> In above same cooling device cdev is binded to trip no 2,3 and 4 with
>> inst_id generated as 1,2,3 respectively. so set_cur_state for those
>> trip reached will be called as,
>> set_cur_state(cdev, 1);
>> set_cur_state(cdev, 2);
>> set_cur_state(cdev, 3);
>
> In this case, why a simple state = get_cur_state() followed by a
> set_cur_state(++state) / set_cur_state(--state) is not enough?

Thanks for looking into the patch. Well actually what you are
suggesting is exactly happening in PASSIVE trip types where the states
are incremented or decremented based on thermal trend. On the contrary
what this part of code is doing is to jump to a fixed state as and
when a trip point is reached. The cooling effect of a frequency level
is known beforehand and hence jumping into that is safe and also this
does not cause performance degradation by going into a much lower
frequency state just for temperature stablization.

>
> Another thing is if we want to do jumps in the sequence?
>
>  set_cur_state(cdev, 1);
>  set_cur_state(cdev, 3);
>  set_cur_state(cdev, 6);
>
> But for that we need a table mapping, trip vs. state.
>
>
> What do you think?
In the current thermal_zone_device_update implementation all the
checks are currently based on increase in temperature. So even though
we want to go to set_cur_state(cdev, 6) we have to follow
set_cur_state(cdev, 1), set_cur_state(cdev, 2) ,..... and finally
set_cur_state(cdev, 6). So mapping table may not be needed as state
transition is one by one. This a type of limitation but I think there
can be some kind of modification in the way the
thermal_zone_device_update calls all the lower temperature cooling
devices instead of jumping directly to the final trip point cooling
devices.
>>
>> Thanks,
>> Amit D
>>
>> >
>> > Thanks,
>> > Durga
>> >
>> >> +
>> >> +                             cdev = instance->cdev;
>> >> +                             cdev->ops->get_max_state(cdev, &max_state);
>> >> +
>> >> +                             if ((temp >= trip_temp) &&
>> >> +                                             (inst_id <= max_state))
>> >> +                                     cdev->ops->set_cur_state(cdev, inst_id);
>> >> +                             else if ((temp < trip_temp) &&
>> >> +                                             (--inst_id <= max_state))
>> >> +                                     cdev->ops->set_cur_state(cdev, inst_id);
>> >> +
>> >> +                             last_trip_change = trip_temp;
>> >> +                     }
>> >> +                     break;
>> >>               case THERMAL_TRIP_PASSIVE:
>> >>                       if (temp >= trip_temp || tz->passive)
>> >>                               thermal_zone_device_passive(tz, temp,
>> >> diff --git a/include/linux/thermal.h b/include/linux/thermal.h
>> >> index 796f1ff..8df901f 100644
>> >> --- a/include/linux/thermal.h
>> >> +++ b/include/linux/thermal.h
>> >> @@ -42,6 +42,7 @@ enum thermal_trip_type {
>> >>       THERMAL_TRIP_PASSIVE,
>> >>       THERMAL_TRIP_HOT,
>> >>       THERMAL_TRIP_CRITICAL,
>> >> +     THERMAL_TRIP_STATE_ACTIVE,
>> >>  };
>> >>
>> >>  struct thermal_zone_device_ops {
>> >> --
>> >> 1.7.1
>> >
>> _______________________________________________
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>> https://lists.linuxfoundation.org/mailman/listinfo/linux-pm
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