cpufreq: intel_pstate: Reduce impact due to rounding error

When policy->max and policy->min are same, in some cases they don't
result in the same frequency cap. The max_policy_pct is rounded up but
not min_perf_pct. So even when they are same, results in different
percentage or maximum and minimum.
Since minimum is a conservative value for power, a lower value without
rounding is better in most of the cases, unless user wants
policy->max = policy->min.
This change uses use the same policy percentage when policy->max and
policy->min are same.

Signed-off-by: Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

diff --git a/drivers/cpufreq/intel_pstate.c b/drivers/cpufreq/intel_pstate.c
index b6e9b49bf151cc7c814b6d388433507679430d11..8e7390bb217589f6b65118bebcf16c44c6731048 100644 (file)
--- a/drivers/cpufreq/intel_pstate.c
+++ b/drivers/cpufreq/intel_pstate.c
@@ -1543,11 +1543,17 @@ static void intel_pstate_set_performance_limits(struct perf_limits *limits)
 static void intel_pstate_update_perf_limits(struct cpufreq_policy *policy,
                                            struct perf_limits *limits)
 {
-       limits->min_policy_pct = (policy->min * 100) / policy->cpuinfo.max_freq;
-       limits->min_policy_pct = clamp_t(int, limits->min_policy_pct, 0, 100);
        limits->max_policy_pct = DIV_ROUND_UP(policy->max * 100,
                                              policy->cpuinfo.max_freq);
        limits->max_policy_pct = clamp_t(int, limits->max_policy_pct, 0, 100);
+       if (policy->max == policy->min) {
+               limits->min_policy_pct = limits->max_policy_pct;
+       } else {
+               limits->min_policy_pct = (policy->min * 100) /
+                                               policy->cpuinfo.max_freq;
+               limits->min_policy_pct = clamp_t(int, limits->min_policy_pct,
+                                                0, 100);
+       }
 
        /* Normalize user input to [min_policy_pct, max_policy_pct] */
        limits->min_perf_pct = max(limits->min_policy_pct,