cpufreq: schedutil: clear cached_raw_freq when invalidated

The cpufreq_schedutil governor keeps a cache of the last
raw frequency that was mapped to a supported device frequency.
If the next request for a frequency matches the cached
value, the policy's next_freq value is reused. But there
are paths that can update the raw cached value without
updating the next_freq value, and there are paths that
can set the next_freq value without setting the raw
cached value. On those paths, the cached value
must be reset.

The case that has been observed is when a frequency request
reaches sugov_update_commit but is then rejected by to
the sugov_up_down_rate_limit check.

Bug: 116279565
Change-Id: I7c585339a04ff1732054d6e5b36a57e2d41266aa
Signed-off-by: John Dias <joaodias@google.com>
Signed-off-by: Miguel de Dios <migueldedios@google.com>
Signed-off-by: Alexander Winkowski <dereference23@outlook.com>

kernel/sched/cpufreq_schedutil.c

@@ -164,8 +164,8 @@ static void sugov_update_commit(struct sugov_policy *sg_policy, u64 time,
 		return;
 
 	if (sugov_up_down_rate_limit(sg_policy, time, next_freq)) {
-		/* Restore cached freq as next_freq is not changed */
-		sg_policy->cached_raw_freq = sg_policy->prev_cached_raw_freq;
+		/* Don't cache a raw freq that didn't become next_freq */
+		sg_policy->cached_raw_freq = 0;
 		return;
 	}
 
@@ -334,8 +334,9 @@ static void sugov_update_single(struct update_util_data *hook, u64 time,
 
 	busy = use_pelt() && sugov_cpu_is_busy(sg_cpu);
 
-	if (0) {
-		sg_policy->cached_raw_freq = sg_policy->prev_cached_raw_freq;
+	if (flags & SCHED_CPUFREQ_RT_DL) {
+		/* clear cache when it's bypassed */
+		sg_policy->cached_raw_freq = 0;
 		next_f = policy->cpuinfo.max_freq;
 	} else {
 		sugov_get_util(&util, &max, sg_cpu->cpu);
@@ -382,8 +383,9 @@ static unsigned int sugov_next_freq_shared(struct sugov_cpu *sg_cpu, u64 time)
 			j_sg_cpu->iowait_boost_pending = false;
 			continue;
 		}
-		if (0) {
-			sg_policy->cached_raw_freq = sg_policy->prev_cached_raw_freq;
+		if (j_sg_cpu->flags & SCHED_CPUFREQ_RT_DL) {
+			/* clear cache when it's bypassed */
+			sg_policy->cached_raw_freq = 0;
 			return policy->cpuinfo.max_freq;
 		}
 
@@ -424,9 +426,10 @@ static void sugov_update_shared(struct update_util_data *hook, u64 time,
 
 	if (sugov_should_update_freq(sg_policy, time) &&
 		!(flags & SCHED_CPUFREQ_CONTINUE)) {
-		if (0) {
+		if (flags & SCHED_CPUFREQ_RT_DL) {
 			next_f = sg_policy->policy->cpuinfo.max_freq;
-			sg_policy->cached_raw_freq = sg_policy->prev_cached_raw_freq;
+			/* clear cache when it's bypassed */
+			sg_policy->cached_raw_freq = 0;
 		} else {
 			next_f = sugov_next_freq_shared(sg_cpu, time);
 		}