[RFT][PATCH v1 3/8] cpufreq/sched: Allow .setpolicy() cpufreq drivers to enable EAS

["Rafael J. Wysocki" <rjw@rjwysocki.net>]

From: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

Some cpufreq drivers, like intel_pstate, have built-in governors that
are used instead of regular cpufreq governors, schedutil in particular,
but they can work with EAS just fine, so allow EAS to be used with
those drivers.

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
---

v0.3 -> v1
     * Rebase on top of the new [1-2/8].
     * Update the diagnostic message printed if the conditions are not met.

This patch is regarded as a cleanup for 6.16.

---
 drivers/cpufreq/cpufreq.c |   13 +++++++++++--
 1 file changed, 11 insertions(+), 2 deletions(-)

--- a/drivers/cpufreq/cpufreq.c
+++ b/drivers/cpufreq/cpufreq.c
@@ -3054,7 +3054,16 @@
 
 	guard(cpufreq_policy_read)(policy);
 
-	return sugov_is_governor(policy);
+	/*
+	 * For EAS compatibility, require that either schedutil is the policy
+	 * governor or the policy is governed directly by the cpufreq driver.
+	 *
+	 * In the latter case, it is assumed that EAS can only be enabled by the
+	 * cpufreq driver itself which will not enable EAS if it does not meet
+	 * the EAS' expectations regarding performance scaling response.
+	 */
+	return sugov_is_governor(policy) || (!policy->governor &&
+		policy->policy != CPUFREQ_POLICY_UNKNOWN);
 }
 
 bool cpufreq_ready_for_eas(const struct cpumask *cpu_mask)
@@ -3064,7 +3073,7 @@
 	/* 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",
+			pr_debug("rd %*pbl: EAS requirements not met\n",
 				 cpumask_pr_args(cpu_mask));
 			return false;
 		}