cpufreq/sched: Move cpufreq-specific EAS checks to cpufreq

Doing cpufreq-specific EAS checks that require accessing policy
internals directly from sched_is_eas_possible() is a bit unfortunate,
so introduce cpufreq_ready_for_eas() in cpufreq, move those checks
into that new function and make sched_is_eas_possible() call it.

While at it, address a possible race between the EAS governor check
and governor change by doing the former under the policy rwsem.

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Reviewed-by: Christian Loehle <christian.loehle@arm.com>
Tested-by: Christian Loehle <christian.loehle@arm.com>
Reviewed-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
Link: https://patch.msgid.link/2317800.iZASKD2KPV@rjwysocki.net

1 files changed, 32 insertions, 0 deletions

diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
index 21fa733a2fe8..731ecfc178d8 100644
--- a/drivers/cpufreq/cpufreq.c
+++ b/drivers/cpufreq/cpufreq.c
@@ -3056,6 +3056,38 @@ static int __init cpufreq_core_init(void)
 
 	return 0;
 }
+
+static bool cpufreq_policy_is_good_for_eas(unsigned int cpu)
+{
+	struct cpufreq_policy *policy __free(put_cpufreq_policy);
+
+	policy = cpufreq_cpu_get(cpu);
+	if (!policy) {
+		pr_debug("cpufreq policy not set for CPU: %d\n", cpu);
+		return false;
+	}
+
+	guard(cpufreq_policy_read)(policy);
+
+	return sugov_is_governor(policy);
+}
+
+bool cpufreq_ready_for_eas(const struct cpumask *cpu_mask)
+{
+	unsigned int cpu;
+
+	/* Do not attempt EAS if schedutil is not being used. */
+	for_each_cpu(cpu, cpu_mask) {
+		if (!cpufreq_policy_is_good_for_eas(cpu)) {
+			pr_debug("rd %*pbl: schedutil is mandatory for EAS\n",
+				 cpumask_pr_args(cpu_mask));
+			return false;
+		}
+	}
+
+	return true;
+}
+
 module_param(off, int, 0444);
 module_param_string(default_governor, default_governor, CPUFREQ_NAME_LEN, 0444);
 core_initcall(cpufreq_core_init);