target/linux/brcm2708/patches-4.19/950-0153-drivers-thermal-step_wise-add-support-for-hysteresis.patch

   1 From 05a13bbd7fbb76b4f690042173749a55d85de831 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
   5  hysteresis
   6
   7 From: Ram Chandrasekar <rkumbako@codeaurora.org>
   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.c | 33 +++++++++++++++++++++++----------
  24  1 file changed, 23 insertions(+), 10 deletions(-)
  25
  26 --- a/drivers/thermal/step_wise.c
  27 +++ b/drivers/thermal/step_wise.c
  28 @@ -36,7 +36,7 @@
  29   *       for this trip point
  30   *    d. if the trend is THERMAL_TREND_DROP_FULL, use lower limit
  31   *       for this trip point
  32 - * If the temperature is lower than a trip point,
  33 + * If the temperature is lower than a hysteresis temperature,
  34   *    a. if the trend is THERMAL_TREND_RAISING, do nothing
  35   *    b. if the trend is THERMAL_TREND_DROPPING, use lower cooling
  36   *       state for this trip point, if the cooling state already
  37 @@ -127,7 +127,7 @@ static void update_passive_instance(stru
  38
  39  static void thermal_zone_trip_update(struct thermal_zone_device *tz, int trip)
  40  {
  41 -       int trip_temp;
  42 +       int trip_temp, hyst_temp;
  43         enum thermal_trip_type trip_type;
  44         enum thermal_trend trend;
  45         struct thermal_instance *instance;
  46 @@ -135,22 +135,23 @@ static void thermal_zone_trip_update(str
  47         int old_target;
  48
  49         if (trip == THERMAL_TRIPS_NONE) {
  50 -               trip_temp = tz->forced_passive;
  51 +               hyst_temp = trip_temp = tz->forced_passive;
  52                 trip_type = THERMAL_TRIPS_NONE;
  53         } else {
  54                 tz->ops->get_trip_temp(tz, trip, &trip_temp);
  55 +               hyst_temp = trip_temp;
  56 +               if (tz->ops->get_trip_hyst) {
  57 +                       tz->ops->get_trip_hyst(tz, trip, &hyst_temp);
  58 +                       hyst_temp = trip_temp - hyst_temp;
  59 +               }
  60                 tz->ops->get_trip_type(tz, trip, &trip_type);
  61         }
  62
  63         trend = get_tz_trend(tz, trip);
  64
  65 -       if (tz->temperature >= trip_temp) {
  66 -               throttle = true;
  67 -               trace_thermal_zone_trip(tz, trip, trip_type);
  68 -       }
  69 -
  70 -       dev_dbg(&tz->device, "Trip%d[type=%d,temp=%d]:trend=%d,throttle=%d\n",
  71 -                               trip, trip_type, trip_temp, trend, throttle);
  72 +       dev_dbg(&tz->device,
  73 +               "Trip%d[type=%d,temp=%d,hyst=%d]:trend=%d,throttle=%d\n",
  74 +               trip, trip_type, trip_temp, hyst_temp, trend, throttle);
  75
  76         mutex_lock(&tz->lock);
  77
  78 @@ -159,6 +160,18 @@ static void thermal_zone_trip_update(str
  79                         continue;
  80
  81                 old_target = instance->target;
  82 +               throttle = false;
  83 +               /*
  84 +                * Lower the mitigation only if the temperature
  85 +                * goes below the hysteresis temperature.
  86 +                */
  87 +               if (tz->temperature >= trip_temp ||
  88 +                  (tz->temperature >= hyst_temp &&
  89 +                  old_target != THERMAL_NO_TARGET)) {
  90 +                       throttle = true;
  91 +                       trace_thermal_zone_trip(tz, trip, trip_type);
  92 +               }
  93 +
  94                 instance->target = get_target_state(instance, trend, throttle);
  95                 dev_dbg(&instance->cdev->device, "old_target=%d, target=%d\n",
  96                                         old_target, (int)instance->target);