cpufreq: Add an interface to mark inefficient frequencies

Some SoCs such as the sd855 have OPPs within the same policy whose cost is
higher than others with a higher frequency. Those OPPs are inefficients
and it might be interesting for a governor to not use them.

cpufreq_table_set_inefficient() allows the caller to identify a specified
frequency as being inefficient. Inefficient frequencies are only supported
on sorted tables.
Signed-off-by: Vincent Donnefort <vincent.donnefort@arm.com>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

include/linux/cpufreq.h

@@ -660,10 +660,11 @@ struct governor_attr {
  *********************************************************************/
 
 /* Special Values of .frequency field */
-#define CPUFREQ_ENTRY_INVALID	~0u
-#define CPUFREQ_TABLE_END	~1u
+#define CPUFREQ_ENTRY_INVALID		~0u
+#define CPUFREQ_TABLE_END		~1u
 /* Special Values of .flags field */
-#define CPUFREQ_BOOST_FREQ	(1 << 0)
+#define CPUFREQ_BOOST_FREQ		(1 << 0)
+#define CPUFREQ_INEFFICIENT_FREQ	(1 << 1)
 
 struct cpufreq_frequency_table {
 	unsigned int	flags;
@@ -1003,6 +1004,36 @@ static inline int cpufreq_table_count_valid_entries(const struct cpufreq_policy
 	return count;
 }
 
+/**
+ * cpufreq_table_set_inefficient() - Mark a frequency as inefficient
+ * @policy:	the &struct cpufreq_policy containing the inefficient frequency
+ * @frequency:	the inefficient frequency
+ *
+ * The &struct cpufreq_policy must use a sorted frequency table
+ *
+ * Return:	%0 on success or a negative errno code
+ */
+
+static inline int
+cpufreq_table_set_inefficient(struct cpufreq_policy *policy,
+			      unsigned int frequency)
+{
+	struct cpufreq_frequency_table *pos;
+
+	/* Not supported */
+	if (policy->freq_table_sorted == CPUFREQ_TABLE_UNSORTED)
+		return -EINVAL;
+
+	cpufreq_for_each_valid_entry(pos, policy->freq_table) {
+		if (pos->frequency == frequency) {
+			pos->flags |= CPUFREQ_INEFFICIENT_FREQ;
+			return 0;
+		}
+	}
+
+	return -EINVAL;
+}
+
 static inline int parse_perf_domain(int cpu, const char *list_name,
 				    const char *cell_name)
 {
@@ -1071,6 +1102,13 @@ static inline bool policy_has_boost_freq(struct cpufreq_policy *policy)
 	return false;
 }
 
+static inline int
+cpufreq_table_set_inefficient(struct cpufreq_policy *policy,
+			      unsigned int frequency)
+{
+	return -EINVAL;
+}
+
 static inline int of_perf_domain_get_sharing_cpumask(int pcpu, const char *list_name,
 						     const char *cell_name, struct cpumask *cpumask)
 {