ANDROID: cpufreq: arch_topology: implement max frequency capping

Implements the Max Frequency Capping Engine (MFCE) getter function
topology_get_max_freq_scale() to provide the scheduler with a
maximum frequency scaling correction factor for more accurate cpu
capacity handling by being able to deal with max frequency capping.

This scaling factor describes the influence of running a cpu with a
current maximum frequency (policy) lower than the maximum possible
frequency (cpuinfo).

The factor is:

  policy_max_freq(cpu) << SCHED_CAPACITY_SHIFT / cpuinfo_max_freq(cpu)

It also implements the MFCE setter function arch_set_max_freq_scale()
which is called from cpufreq_set_policy().

Change-Id: I59e52861ee260755ab0518fe1f7183a2e4e3d0fc
Signed-off-by: Ionela Voinescu <ionela.voinescu@arm.com>
Signed-off-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
[Trivial cherry-pick issue in cpufreq.c]
Signed-off-by: Quentin Perret <quentin.perret@arm.com>

drivers/base/arch_topology.c

@@ -22,6 +22,8 @@
 #include <linux/smp.h>
 
 DEFINE_PER_CPU(unsigned long, freq_scale) = SCHED_CAPACITY_SCALE;
+DEFINE_PER_CPU(unsigned long, max_cpu_freq);
+DEFINE_PER_CPU(unsigned long, max_freq_scale) = SCHED_CAPACITY_SCALE;
 
 void arch_set_freq_scale(struct cpumask *cpus, unsigned long cur_freq,
 			 unsigned long max_freq)
@@ -31,8 +33,29 @@ void arch_set_freq_scale(struct cpumask *cpus, unsigned long cur_freq,
 
 	scale = (cur_freq << SCHED_CAPACITY_SHIFT) / max_freq;
 
-	for_each_cpu(i, cpus)
+	for_each_cpu(i, cpus) {
 		per_cpu(freq_scale, i) = scale;
+		per_cpu(max_cpu_freq, i) = max_freq;
+	}
+}
+
+void arch_set_max_freq_scale(struct cpumask *cpus,
+			     unsigned long policy_max_freq)
+{
+	unsigned long scale, max_freq;
+	int cpu = cpumask_first(cpus);
+
+	if (cpu > nr_cpu_ids)
+		return;
+
+	max_freq = per_cpu(max_cpu_freq, cpu);
+	if (!max_freq)
+		return;
+
+	scale = (policy_max_freq << SCHED_CAPACITY_SHIFT) / max_freq;
+
+	for_each_cpu(cpu, cpus)
+		per_cpu(max_freq_scale, cpu) = scale;
 }
 
 DEFINE_PER_CPU(unsigned long, cpu_scale) = SCHED_CAPACITY_SCALE;

drivers/cpufreq/cpufreq.c

@@ -152,6 +152,12 @@ __weak void arch_set_freq_scale(struct cpumask *cpus, unsigned long cur_freq,
 }
 EXPORT_SYMBOL_GPL(arch_set_freq_scale);
 
+__weak void arch_set_max_freq_scale(struct cpumask *cpus,
+				    unsigned long policy_max_freq)
+{
+}
+EXPORT_SYMBOL_GPL(arch_set_max_freq_scale);
+
 /*
  * This is a generic cpufreq init() routine which can be used by cpufreq
  * drivers of SMP systems. It will do following:
@@ -2398,6 +2404,8 @@ int cpufreq_set_policy(struct cpufreq_policy *policy,
 	policy->max = new_policy->max;
 	trace_cpu_frequency_limits(policy);
 
+	arch_set_max_freq_scale(policy->cpus, policy->max);
+
 	policy->cached_target_freq = UINT_MAX;
 
 	pr_debug("new min and max freqs are %u - %u kHz\n",

include/linux/arch_topology.h

@@ -33,6 +33,14 @@ unsigned long topology_get_freq_scale(int cpu)
 	return per_cpu(freq_scale, cpu);
 }
 
+DECLARE_PER_CPU(unsigned long, max_freq_scale);
+
+static inline
+unsigned long topology_get_max_freq_scale(struct sched_domain *sd, int cpu)
+{
+	return per_cpu(max_freq_scale, cpu);
+}
+
 struct cpu_topology {
 	int thread_id;
 	int core_id;

include/linux/cpufreq.h

@@ -984,6 +984,8 @@ extern unsigned int arch_freq_get_on_cpu(int cpu);
 
 extern void arch_set_freq_scale(struct cpumask *cpus, unsigned long cur_freq,
 				unsigned long max_freq);
+extern void arch_set_max_freq_scale(struct cpumask *cpus,
+				    unsigned long policy_max_freq);
 
 /* the following are really really optional */
 extern struct freq_attr cpufreq_freq_attr_scaling_available_freqs;