releases/4.8.5/cpufreq-conservative-fix-next-frequency-selection.patch

   1 From abb6627910a1e783c8e034b35b7c80e5e7f98f41 Mon Sep 17 00:00:00 2001
   2 From: "Rafael J. Wysocki" <rafael.j.wysocki@intel.com>
   3 Date: Wed, 12 Oct 2016 21:47:03 +0200
   4 Subject: cpufreq: conservative: Fix next frequency selection
   5
   6 From: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
   7
   8 commit abb6627910a1e783c8e034b35b7c80e5e7f98f41 upstream.
   9
  10 Commit d352cf47d93e (cpufreq: conservative: Do not use transition
  11 notifications) overlooked the case when the "frequency step" used
  12 by the conservative governor is small relative to the distances
  13 between the available frequencies and broke the algorithm by
  14 using policy->cur instead of the previously requested frequency
  15 when computing the next one.
  16
  17 As a result, the governor may not be able to go outside of a narrow
  18 range between two consecutive available frequencies.
  19
  20 Fix the problem by making the governor save the previously requested
  21 frequency and select the next one relative that value (unless it is
  22 out of range, in which case policy->cur will be used instead).
  23
  24 Fixes: d352cf47d93e (cpufreq: conservative: Do not use transition notifications)
  25 Link: https://bugzilla.kernel.org/show_bug.cgi?id=177171
  26 Reported-and-tested-by: Aleksey Rybalkin <aleksey@rybalkin.org>
  27 Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
  28 Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
  29 Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
  30
  31 ---
  32  drivers/cpufreq/cpufreq_conservative.c |   19 ++++++++++++++++---
  33  1 file changed, 16 insertions(+), 3 deletions(-)
  34
  35 --- a/drivers/cpufreq/cpufreq_conservative.c
  36 +++ b/drivers/cpufreq/cpufreq_conservative.c
  37 @@ -17,6 +17,7 @@
  38  struct cs_policy_dbs_info {
  39         struct policy_dbs_info policy_dbs;
  40         unsigned int down_skip;
  41 +       unsigned int requested_freq;
  42  };
  43
  44  static inline struct cs_policy_dbs_info *to_dbs_info(struct policy_dbs_info *policy_dbs)
  45 @@ -61,6 +62,7 @@ static unsigned int cs_dbs_timer(struct
  46  {
  47         struct policy_dbs_info *policy_dbs = policy->governor_data;
  48         struct cs_policy_dbs_info *dbs_info = to_dbs_info(policy_dbs);
  49 +       unsigned int requested_freq = dbs_info->requested_freq;
  50         struct dbs_data *dbs_data = policy_dbs->dbs_data;
  51         struct cs_dbs_tuners *cs_tuners = dbs_data->tuners;
  52         unsigned int load = dbs_update(policy);
  53 @@ -72,10 +74,16 @@ static unsigned int cs_dbs_timer(struct
  54         if (cs_tuners->freq_step == 0)
  55                 goto out;
  56
  57 +       /*
  58 +        * If requested_freq is out of range, it is likely that the limits
  59 +        * changed in the meantime, so fall back to current frequency in that
  60 +        * case.
  61 +        */
  62 +       if (requested_freq > policy->max || requested_freq < policy->min)
  63 +               requested_freq = policy->cur;
  64 +
  65         /* Check for frequency increase */
  66         if (load > dbs_data->up_threshold) {
  67 -               unsigned int requested_freq = policy->cur;
  68 -
  69                 dbs_info->down_skip = 0;
  70
  71                 /* if we are already at full speed then break out early */
  72 @@ -83,8 +91,11 @@ static unsigned int cs_dbs_timer(struct
  73                         goto out;
  74
  75                 requested_freq += get_freq_target(cs_tuners, policy);
  76 +               if (requested_freq > policy->max)
  77 +                       requested_freq = policy->max;
  78
  79                 __cpufreq_driver_target(policy, requested_freq, CPUFREQ_RELATION_H);
  80 +               dbs_info->requested_freq = requested_freq;
  81                 goto out;
  82         }
  83
  84 @@ -95,7 +106,7 @@ static unsigned int cs_dbs_timer(struct
  85
  86         /* Check for frequency decrease */
  87         if (load < cs_tuners->down_threshold) {
  88 -               unsigned int freq_target, requested_freq = policy->cur;
  89 +               unsigned int freq_target;
  90                 /*
  91                  * if we cannot reduce the frequency anymore, break out early
  92                  */
  93 @@ -109,6 +120,7 @@ static unsigned int cs_dbs_timer(struct
  94                         requested_freq = policy->min;
  95
  96                 __cpufreq_driver_target(policy, requested_freq, CPUFREQ_RELATION_L);
  97 +               dbs_info->requested_freq = requested_freq;
  98         }
  99
 100   out:
 101 @@ -287,6 +299,7 @@ static void cs_start(struct cpufreq_poli
 102         struct cs_policy_dbs_info *dbs_info = to_dbs_info(policy->governor_data);
 103
 104         dbs_info->down_skip = 0;
 105 +       dbs_info->requested_freq = policy->cur;
 106  }
 107
 108  static struct dbs_governor cs_governor = {