cpufreq: Avoid redundant target() calls for unchanged limits

Drivers setting CPUFREQ_NEED_UPDATE_LIMITS expect target() to be
invoked even if the target frequency remains unchanged, so they can
update their internal policy limits state.

Currently the core invokes target() unconditionally whenever the
requested frequency matches policy->cur for such drivers, even if
policy->min and policy->max haven't changed since the previous update.

Track pending policy limit updates explicitly and skip redundant
target() invocations when neither the target frequency nor the
effective limits changed.

Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
Reviewed-by: Lifeng Zheng <zhenglifeng1@huawei.com>
Reviewed-by: Zhongqiu Han <zhongqiu.han@oss.qualcomm.com>
Link: https://patch.msgid.link/d0107c364b709abca21acf88072220bc05478594.1779423281.git.viresh.kumar@linaro.org
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

2 files changed, 25 insertions, 9 deletions

diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
index d41067cd1f1b..4e78f4caab3a 100644
--- a/drivers/cpufreq/cpufreq.c
+++ b/drivers/cpufreq/cpufreq.c
@@ -2368,9 +2368,13 @@ int __cpufreq_driver_target(struct cpufreq_policy *policy,
 	 * exactly same freq is called again and so we can save on few function
 	 * calls.
 	 */
-	if (target_freq == policy->cur &&
-	    !(cpufreq_driver->flags & CPUFREQ_NEED_UPDATE_LIMITS))
-		return 0;
+	if (target_freq == policy->cur) {
+		if (!(cpufreq_driver->flags & CPUFREQ_NEED_UPDATE_LIMITS) ||
+		    !policy->update_limits)
+			return 0;
+
+		policy->update_limits = false;
+	}
 
 	if (cpufreq_driver->target) {
 		/*
@@ -2622,6 +2626,7 @@ static int cpufreq_set_policy(struct cpufreq_policy *policy,
 {
 	struct cpufreq_policy_data new_data;
 	struct cpufreq_governor *old_gov;
+	unsigned int freq;
 	int ret;
 
 	memcpy(&new_data.cpuinfo, &policy->cpuinfo, sizeof(policy->cpuinfo));
@@ -2654,12 +2659,20 @@ static int cpufreq_set_policy(struct cpufreq_policy *policy,
 	 * compiler optimizations around them because they may be accessed
 	 * concurrently by cpufreq_driver_resolve_freq() during the update.
 	 */
-	WRITE_ONCE(policy->max, __resolve_freq(policy, new_data.max,
-					       new_data.min, new_data.max,
-					       CPUFREQ_RELATION_H));
-	new_data.min = __resolve_freq(policy, new_data.min, new_data.min,
-				      new_data.max, CPUFREQ_RELATION_L);
-	WRITE_ONCE(policy->min, new_data.min > policy->max ? policy->max : new_data.min);
+	freq = __resolve_freq(policy, new_data.max, new_data.min, new_data.max,
+			      CPUFREQ_RELATION_H);
+	if (freq != policy->max) {
+		WRITE_ONCE(policy->max, freq);
+		policy->update_limits = true;
+	}
+
+	freq = __resolve_freq(policy, new_data.min, new_data.min, new_data.max,
+			      CPUFREQ_RELATION_L);
+	freq = min(freq, policy->max);
+	if (freq != policy->min) {
+		WRITE_ONCE(policy->min, freq);
+		policy->update_limits = true;
+	}
 
 	trace_cpu_frequency_limits(policy);
 
diff --git a/include/linux/cpufreq.h b/include/linux/cpufreq.h
index 4d4b4ed24b30..ae9d1ce4f49c 100644
--- a/include/linux/cpufreq.h
+++ b/include/linux/cpufreq.h
@@ -146,6 +146,9 @@ struct cpufreq_policy {
 	/* Per policy boost supported flag. */
 	bool			boost_supported;
 
+	/* Pending policy->min/max update for the driver */
+	bool			update_limits;
+
 	 /* Cached frequency lookup from cpufreq_driver_resolve_freq. */
 	unsigned int cached_target_freq;
 	unsigned int cached_resolved_idx;