From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: Quentin Perret <qperret@google.com>
Date: Fri, 5 Jun 2020 09:06:50 +0100
Subject: NOUPSTREAM: ANDROID: sched: Allow EAS without schedutil

This effectively reverts 531b5c9f5cd0 ("sched/topology: Make Energy
Aware Scheduling depend on schedutil"), and updates the documentation
accordingly.

In the context of GKI 2.0, some partners need to use a custom cpufreq
govenor, but would like to keep EAS enabled.

Remove the hard dependency between them.

[CPNOTE: 30/06/21] Lee: Attempt was made to upstream - it was NACKed

Bug: 157580690
Bug: 120440300
Link: https://lore.kernel.org/lkml/20200507181012.29791-1-qperret@google.com/
Signed-off-by: Quentin Perret <qperret@google.com>
Change-Id: Ied1c5aba6b692e26776b3e2c050780a67cc5bae1
---
 Documentation/scheduler/sched-energy.rst |  2 +-
 drivers/cpufreq/cpufreq.c                |  1 -
 include/linux/cpufreq.h                  |  8 --------
 kernel/sched/cpufreq_schedutil.c         | 26 ------------------------
 kernel/sched/topology.c                  | 19 +----------------
 5 files changed, 2 insertions(+), 54 deletions(-)

diff --git a/Documentation/scheduler/sched-energy.rst b/Documentation/scheduler/sched-energy.rst
--- a/Documentation/scheduler/sched-energy.rst
+++ b/Documentation/scheduler/sched-energy.rst
@@ -402,7 +402,7 @@ Consequently, the only sane governor to use together with EAS is schedutil,
 because it is the only one providing some degree of consistency between
 frequency requests and energy predictions.
 
-Using EAS with any other governor than schedutil is not supported.
+Using EAS with any other governor than schedutil is not recommended.
 
 
 6.5 Scale-invariant utilization signals
diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
--- a/drivers/cpufreq/cpufreq.c
+++ b/drivers/cpufreq/cpufreq.c
@@ -2576,7 +2576,6 @@ static int cpufreq_set_policy(struct cpufreq_policy *policy,
 		ret = cpufreq_start_governor(policy);
 		if (!ret) {
 			pr_debug("governor change\n");
-			sched_cpufreq_governor_change(policy, old_gov);
 			return 0;
 		}
 		cpufreq_exit_governor(policy);
diff --git a/include/linux/cpufreq.h b/include/linux/cpufreq.h
--- a/include/linux/cpufreq.h
+++ b/include/linux/cpufreq.h
@@ -1183,14 +1183,6 @@ static inline int of_perf_domain_get_sharing_cpumask(int pcpu, const char *list_
 }
 #endif
 
-#if defined(CONFIG_ENERGY_MODEL) && defined(CONFIG_CPU_FREQ_GOV_SCHEDUTIL)
-void sched_cpufreq_governor_change(struct cpufreq_policy *policy,
-			struct cpufreq_governor *old_gov);
-#else
-static inline void sched_cpufreq_governor_change(struct cpufreq_policy *policy,
-			struct cpufreq_governor *old_gov) { }
-#endif
-
 extern void arch_freq_prepare_all(void);
 extern unsigned int arch_freq_get_on_cpu(int cpu);
 
diff --git a/kernel/sched/cpufreq_schedutil.c b/kernel/sched/cpufreq_schedutil.c
--- a/kernel/sched/cpufreq_schedutil.c
+++ b/kernel/sched/cpufreq_schedutil.c
@@ -835,29 +835,3 @@ struct cpufreq_governor *cpufreq_default_governor(void)
 #endif
 
 cpufreq_governor_init(schedutil_gov);
-
-#ifdef CONFIG_ENERGY_MODEL
-static void rebuild_sd_workfn(struct work_struct *work)
-{
-	rebuild_sched_domains_energy();
-}
-static DECLARE_WORK(rebuild_sd_work, rebuild_sd_workfn);
-
-/*
- * EAS shouldn't be attempted without sugov, so rebuild the sched_domains
- * on governor changes to make sure the scheduler knows about it.
- */
-void sched_cpufreq_governor_change(struct cpufreq_policy *policy,
-				  struct cpufreq_governor *old_gov)
-{
-	if (old_gov == &schedutil_gov || policy->governor == &schedutil_gov) {
-		/*
-		 * When called from the cpufreq_register_driver() path, the
-		 * cpu_hotplug_lock is already held, so use a work item to
-		 * avoid nested locking in rebuild_sched_domains().
-		 */
-		schedule_work(&rebuild_sd_work);
-	}
-
-}
-#endif
diff --git a/kernel/sched/topology.c b/kernel/sched/topology.c
--- a/kernel/sched/topology.c
+++ b/kernel/sched/topology.c
@@ -327,8 +327,7 @@ static void sched_energy_set(bool has_eas)
  *    2. the SD_ASYM_CPUCAPACITY flag is set in the sched_domain hierarchy.
  *    3. no SMT is detected.
  *    4. the EM complexity is low enough to keep scheduling overheads low;
- *    5. schedutil is driving the frequency of all CPUs of the rd;
- *    6. frequency invariance support is present;
+ *    5. frequency invariance support is present;
  *
  * The complexity of the Energy Model is defined as:
  *
@@ -348,15 +347,12 @@ static void sched_energy_set(bool has_eas)
  */
 #define EM_MAX_COMPLEXITY 2048
 
-extern struct cpufreq_governor schedutil_gov;
 static bool build_perf_domains(const struct cpumask *cpu_map)
 {
 	int i, nr_pd = 0, nr_ps = 0, nr_cpus = cpumask_weight(cpu_map);
 	struct perf_domain *pd = NULL, *tmp;
 	int cpu = cpumask_first(cpu_map);
 	struct root_domain *rd = cpu_rq(cpu)->rd;
-	struct cpufreq_policy *policy;
-	struct cpufreq_governor *gov;
 
 	if (!sysctl_sched_energy_aware)
 		goto free;
@@ -390,19 +386,6 @@ static bool build_perf_domains(const struct cpumask *cpu_map)
 		if (find_pd(pd, i))
 			continue;
 
-		/* Do not attempt EAS if schedutil is not being used. */
-		policy = cpufreq_cpu_get(i);
-		if (!policy)
-			goto free;
-		gov = policy->governor;
-		cpufreq_cpu_put(policy);
-		if (gov != &schedutil_gov) {
-			if (rd->pd)
-				pr_warn("rd %*pbl: Disabling EAS, schedutil is mandatory\n",
-						cpumask_pr_args(cpu_map));
-			goto free;
-		}
-
 		/* Create the new pd and add it to the local list. */
 		tmp = pd_init(i);
 		if (!tmp)