Merge back intel_pstate fixes for v4.6.

* pm-cpufreq:
  intel_pstate: Avoid extra invocation of intel_pstate_sample()
  intel_pstate: Do not set utilization update hook too early

Author: rafaeljw

drivers/cpufreq/intel_pstate.c

@@ -910,7 +910,14 @@ static inline bool intel_pstate_sample(struct cpudata *cpu, u64 time)
 	cpu->prev_aperf = aperf;
 	cpu->prev_mperf = mperf;
 	cpu->prev_tsc = tsc;
-	return true;
+	/*
+	 * First time this function is invoked in a given cycle, all of the
+	 * previous sample data fields are equal to zero or stale and they must
+	 * be populated with meaningful numbers for things to work, so assume
+	 * that sample.time will always be reset before setting the utilization
+	 * update hook and make the caller skip the sample then.
+	 */
+	return !!cpu->last_sample_time;
 }
 
 static inline int32_t get_avg_frequency(struct cpudata *cpu)
@@ -984,8 +991,7 @@ static inline int32_t get_target_pstate_use_performance(struct cpudata *cpu)
 	 * enough period of time to adjust our busyness.
 	 */
 	duration_ns = cpu->sample.time - cpu->last_sample_time;
-	if ((s64)duration_ns > pid_params.sample_rate_ns * 3
-	    && cpu->last_sample_time > 0) {
+	if ((s64)duration_ns > pid_params.sample_rate_ns * 3) {
 		sample_ratio = div_fp(int_tofp(pid_params.sample_rate_ns),
 				      int_tofp(duration_ns));
 		core_busy = mul_fp(core_busy, sample_ratio);
@@ -1100,10 +1106,8 @@ static int intel_pstate_init_cpu(unsigned int cpunum)
 	intel_pstate_get_cpu_pstates(cpu);
 
 	intel_pstate_busy_pid_reset(cpu);
-	intel_pstate_sample(cpu, 0);
 
 	cpu->update_util.func = intel_pstate_update_util;
-	cpufreq_set_update_util_data(cpunum, &cpu->update_util);
 
 	pr_debug("intel_pstate: controlling: cpu %d\n", cpunum);
 
@@ -1122,18 +1126,33 @@ static unsigned int intel_pstate_get(unsigned int cpu_num)
 	return get_avg_frequency(cpu);
 }
 
+static void intel_pstate_set_update_util_hook(unsigned int cpu_num)
+{
+	struct cpudata *cpu = all_cpu_data[cpu_num];
+
+	/* Prevent intel_pstate_update_util() from using stale data. */
+	cpu->sample.time = 0;
+	cpufreq_set_update_util_data(cpu_num, &cpu->update_util);
+}
+
+static void intel_pstate_clear_update_util_hook(unsigned int cpu)
+{
+	cpufreq_set_update_util_data(cpu, NULL);
+	synchronize_sched();
+}
+
 static int intel_pstate_set_policy(struct cpufreq_policy *policy)
 {
 	if (!policy->cpuinfo.max_freq)
 		return -ENODEV;
 
+	intel_pstate_clear_update_util_hook(policy->cpu);
+
 	if (policy->policy == CPUFREQ_POLICY_PERFORMANCE &&
 	    policy->max >= policy->cpuinfo.max_freq) {
 		pr_debug("intel_pstate: set performance\n");
 		limits = &performance_limits;
-		if (hwp_active)
-			intel_pstate_hwp_set(policy->cpus);
-		return 0;
+		goto out;
 	}
 
 	pr_debug("intel_pstate: set powersave\n");
@@ -1163,6 +1182,9 @@ static int intel_pstate_set_policy(struct cpufreq_policy *policy)
 	limits->max_perf = div_fp(int_tofp(limits->max_perf_pct),
 				  int_tofp(100));
 
+ out:
+	intel_pstate_set_update_util_hook(policy->cpu);
+
 	if (hwp_active)
 		intel_pstate_hwp_set(policy->cpus);
 
@@ -1187,8 +1209,7 @@ static void intel_pstate_stop_cpu(struct cpufreq_policy *policy)
 
 	pr_debug("intel_pstate: CPU %d exiting\n", cpu_num);
 
-	cpufreq_set_update_util_data(cpu_num, NULL);
-	synchronize_sched();
+	intel_pstate_clear_update_util_hook(cpu_num);
 
 	if (hwp_active)
 		return;
@@ -1455,8 +1476,7 @@ static int __init intel_pstate_init(void)
 	get_online_cpus();
 	for_each_online_cpu(cpu) {
 		if (all_cpu_data[cpu]) {
-			cpufreq_set_update_util_data(cpu, NULL);
-			synchronize_sched();
+			intel_pstate_clear_update_util_hook(cpu);
 			kfree(all_cpu_data[cpu]);
 		}
 	}