[PATCH 2/2] cpufreq: governor: Apply limits with requested_freq or next_freq

[Lifeng Zheng]

For conservative, ondemand and schedutil governor,
cpufreq_policy_apply_limits() is called in .limits(). This function updates
the target because the limits (policy->max and policy->min) may be changed.
However, it uses policy->cur as the reference for the target frequency.
This may cause some problems because the value of policy->cur is influenced
by a variety of factors.

For example, for some reason, the platform determines a final
frequency divided from the frequency distributed by the OS, and this is
reflected in policy->cur. After that, cpufreq_policy_apply_limits() is
called and because policy->cur is out of limmit, policy->min will be used
as the new target. This caused the real frequency lower but it's
unnecessary. Consertative and ondemand governor use requested_freq and
schedutil governor uses next_freq to represent the target frequency. It's
more reasonable to use them in cpufreq_policy_apply_limits().

At the same time, use policy->cur as the initial value of next_freq in
schedutil governor's start() callback.

Signed-off-by: Lifeng Zheng <zhenglifeng1@xxxxxxxxxx>
---
 drivers/cpufreq/cpufreq_governor.c | 2 +-
 include/linux/cpufreq.h            | 7 ++++---
 kernel/sched/cpufreq_schedutil.c   | 4 ++--
 3 files changed, 7 insertions(+), 6 deletions(-)

diff --git a/drivers/cpufreq/cpufreq_governor.c b/drivers/cpufreq/cpufreq_governor.c
index 7ec38407230f..dade45f7e57c 100644
--- a/drivers/cpufreq/cpufreq_governor.c
+++ b/drivers/cpufreq/cpufreq_governor.c
@@ -573,7 +573,7 @@ void cpufreq_dbs_governor_limits(struct cpufreq_policy *policy)
 		goto out;
 
 	mutex_lock(&policy_dbs->update_mutex);
-	cpufreq_policy_apply_limits(policy);
+	cpufreq_policy_apply_limits(policy, policy_dbs->requested_freq);
 	gov_update_sample_delay(policy_dbs, 0);
 	mutex_unlock(&policy_dbs->update_mutex);
 
diff --git a/include/linux/cpufreq.h b/include/linux/cpufreq.h
index 0465d1e6f72a..4d7341ef3645 100644
--- a/include/linux/cpufreq.h
+++ b/include/linux/cpufreq.h
@@ -657,12 +657,13 @@ static inline bool sugov_is_governor(struct cpufreq_policy *policy)
 }
 #endif
 
-static inline void cpufreq_policy_apply_limits(struct cpufreq_policy *policy)
+static inline void cpufreq_policy_apply_limits(struct cpufreq_policy *policy,
+					       unsigned int target_freq)
 {
-	if (policy->max < policy->cur)
+	if (policy->max < target_freq)
 		__cpufreq_driver_target(policy, policy->max,
 					CPUFREQ_RELATION_HE);
-	else if (policy->min > policy->cur)
+	else if (policy->min > target_freq)
 		__cpufreq_driver_target(policy, policy->min,
 					CPUFREQ_RELATION_LE);
 }
diff --git a/kernel/sched/cpufreq_schedutil.c b/kernel/sched/cpufreq_schedutil.c
index 0ab5f9d4bc59..8d239fe3afa8 100644
--- a/kernel/sched/cpufreq_schedutil.c
+++ b/kernel/sched/cpufreq_schedutil.c
@@ -848,7 +848,7 @@ static int sugov_start(struct cpufreq_policy *policy)
 
 	sg_policy->freq_update_delay_ns	= sg_policy->tunables->rate_limit_us * NSEC_PER_USEC;
 	sg_policy->last_freq_update_time	= 0;
-	sg_policy->next_freq			= 0;
+	sg_policy->next_freq			= policy->cur;
 	sg_policy->work_in_progress		= false;
 	sg_policy->limits_changed		= false;
 	sg_policy->cached_raw_freq		= 0;
@@ -895,7 +895,7 @@ static void sugov_limits(struct cpufreq_policy *policy)
 
 	if (!policy->fast_switch_enabled) {
 		mutex_lock(&sg_policy->work_lock);
-		cpufreq_policy_apply_limits(policy);
+		cpufreq_policy_apply_limits(policy, sg_policy->next_freq);
 		mutex_unlock(&sg_policy->work_lock);
 	}
 
-- 
2.33.0