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   1 From cef4ba037209392aa6437357c27ba7c450936e36 Mon Sep 17 00:00:00 2001
   2 From: Ram Chandrasekar <rkumbako@codeaurora.org>
   3 Date: Mon, 7 May 2018 11:54:08 -0600
   4 Subject: [PATCH] drivers: thermal: step_wise: add support for hysteresis
   5 MIME-Version: 1.0
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   8
   9 Step wise governor increases the mitigation level when the temperature
  10 goes above a threshold and will decrease the mitigation when the
  11 temperature falls below the threshold. If it were a case, where the
  12 temperature hovers around a threshold, the mitigation will be applied
  13 and removed at every iteration. This reaction to the temperature is
  14 inefficient for performance.
  15
  16 The use of hysteresis temperature could avoid this ping-pong of
  17 mitigation by relaxing the mitigation to happen only when the
  18 temperature goes below this lower hysteresis value.
  19
  20 Signed-off-by: Ram Chandrasekar <rkumbako@codeaurora.org>
  21 Signed-off-by: Lina Iyer <ilina@codeaurora.org>
  22
  23 drivers: thermal: step_wise: avoid throttling at hysteresis temperature after dropping below it
  24
  25 Signed-off-by: Serge Schneider <serge@raspberrypi.org>
  26
  27 Fix hysteresis support in gov_step_wise.c
  28
  29 Directly get hyst value instead of going through an
  30 optional and, now, unimplemented function.
  31
  32 Signed-off-by: Jürgen Kreileder <jk@blackdown.de>
  33 ---
  34  drivers/thermal/gov_step_wise.c | 24 ++++++++++++++++++++----
  35  1 file changed, 20 insertions(+), 4 deletions(-)
  36
  37 --- a/drivers/thermal/gov_step_wise.c
  38 +++ b/drivers/thermal/gov_step_wise.c
  39 @@ -17,11 +17,11 @@
  40  #include "thermal_core.h"
  41
  42  /*
  43 - * If the temperature is higher than a trip point,
  44 + * If the temperature is higher than a hysteresis temperature,
  45   *    a. if the trend is THERMAL_TREND_RAISING, use higher cooling
  46   *       state for this trip point
  47   *    b. if the trend is THERMAL_TREND_DROPPING, do nothing
  48 - * If the temperature is lower than a trip point,
  49 + * If the temperature is lower than a hysteresis temperature,
  50   *    a. if the trend is THERMAL_TREND_RAISING, do nothing
  51   *    b. if the trend is THERMAL_TREND_DROPPING, use lower cooling
  52   *       state for this trip point, if the cooling state already
  53 @@ -74,19 +74,35 @@ static void thermal_zone_trip_update(str
  54         int trip_id = thermal_zone_trip_id(tz, trip);
  55         struct thermal_instance *instance;
  56         bool throttle = false;
  57 +       int hyst_temp;
  58
  59         if (tz->temperature >= trip_threshold) {
  60                 throttle = true;
  61                 trace_thermal_zone_trip(tz, trip_id, trip->type);
  62         }
  63
  64 -       dev_dbg(&tz->device, "Trip%d[type=%d,temp=%d]:trend=%d,throttle=%d\n",
  65 -               trip_id, trip->type, trip_threshold, trend, throttle);
  66 +       hyst_temp = trip->temperature - trip->hysteresis;
  67 +
  68 +       dev_dbg(&tz->device,
  69 +               "Trip%d[type=%d,temp=%d,hyst=%d]:trend=%d,throttle=%d\n",
  70 +               trip_id, trip->type, trip->temperature, hyst_temp, trend, throttle);
  71
  72         list_for_each_entry(instance, &td->thermal_instances, trip_node) {
  73                 int old_target;
  74
  75                 old_target = instance->target;
  76 +               throttle = false;
  77 +               /*
  78 +                * Lower the mitigation only if the temperature
  79 +                * goes below the hysteresis temperature.
  80 +                */
  81 +               if (tz->temperature >= trip->temperature ||
  82 +                  (tz->temperature >= hyst_temp &&
  83 +                  old_target == instance->upper)) {
  84 +                       throttle = true;
  85 +                       trace_thermal_zone_trip(tz, trip_id, trip->type);
  86 +               }
  87 +
  88                 instance->target = get_target_state(instance, trend, throttle);
  89
  90                 dev_dbg(&instance->cdev->device, "old_target=%d, target=%ld\n",