cpufreq: Limit resolving a frequency to policy min/max

Resolving a frequency to an efficient one should not transgress
policy->max (which can be set for thermal reason) and policy->min.

Currently, there is possibility where scaling_cur_freq can exceed
scaling_max_freq when scaling_max_freq is an inefficient frequency.

Add a check to ensure that resolving a frequency will respect
policy->min/max.

Cc: All applicable <[email protected]>
Fixes: 1f39fa0 ("cpufreq: Introducing CPUFREQ_RELATION_E")
Signed-off-by: Shivnandan Kumar <[email protected]>
[ rjw: Whitespace adjustment, changelog edits ]
Signed-off-by: Rafael J. Wysocki <[email protected]>

Author: Shivnandan Kumar

include/linux/cpufreq.h

@@ -1020,6 +1020,18 @@ static inline int cpufreq_table_find_index_c(struct cpufreq_policy *policy,
 						   efficiencies);
 }
 
+static inline bool cpufreq_is_in_limits(struct cpufreq_policy *policy, int idx)
+{
+	unsigned int freq;
+
+	if (idx < 0)
+		return false;
+
+	freq = policy->freq_table[idx].frequency;
+
+	return freq == clamp_val(freq, policy->min, policy->max);
+}
+
 static inline int cpufreq_frequency_table_target(struct cpufreq_policy *policy,
 						 unsigned int target_freq,
 						 unsigned int relation)
@@ -1053,7 +1065,8 @@ static inline int cpufreq_frequency_table_target(struct cpufreq_policy *policy,
 		return 0;
 	}
 
-	if (idx < 0 && efficiencies) {
+	/* Limit frequency index to honor policy->min/max */
+	if (!cpufreq_is_in_limits(policy, idx) && efficiencies) {
 		efficiencies = false;
 		goto retry;
 	}