[PATCH] cpufreq: intel_pstate: Fix HWP on boot CPU after system resume

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

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

Commit 41cfd64cf49fc "Update frequencies of policy->cpus only from
->set_policy()" changed the way the intel_pstate driver's ->set_policy
callback updates the HWP (hardware-managed P-states) settings.
A side effect of it is that if those settings are modified on the
boot CPU during system suspend and wakeup, they will never be
restored during subsequent system resume.

To address this problem, allow cpufreq drivers that don't provide
->target or ->target_index callbacks to use ->suspend and ->resume
callbacks and add a ->resume callback to intel_pstate to restore
the HWP settings on the CPUs that belong to the given policy.

Fixes: 41cfd64cf49fc "Update frequencies of policy->cpus only from ->set_policy()"
Tested-by: Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
---

Note: We've tried to address that issue by adding syscore_ops to
intel_pstate and restoring the boot CPU's HWP setting from a
syscore resume, but that turns out to be too early (apparently,
the processor is not ready for that at that point).

---
 drivers/cpufreq/cpufreq.c      |   28 ++++++++++++++++------------
 drivers/cpufreq/intel_pstate.c |   12 ++++++++++--
 2 files changed, 26 insertions(+), 14 deletions(-)

Index: linux-pm/drivers/cpufreq/intel_pstate.c
===================================================================
--- linux-pm.orig/drivers/cpufreq/intel_pstate.c
+++ linux-pm/drivers/cpufreq/intel_pstate.c
@@ -318,6 +318,14 @@ static void intel_pstate_hwp_set(const s
 	}
 }
 
+static int intel_pstate_hwp_set_policy(struct cpufreq_policy *policy)
+{
+	if (hwp_active)
+		intel_pstate_hwp_set(policy->cpus);
+
+	return 0;
+}
+
 static void intel_pstate_hwp_set_online_cpus(void)
 {
 	get_online_cpus();
@@ -1183,8 +1191,7 @@ static int intel_pstate_set_policy(struc
  out:
 	intel_pstate_set_update_util_hook(policy->cpu);
 
-	if (hwp_active)
-		intel_pstate_hwp_set(policy->cpus);
+	intel_pstate_hwp_set_policy(policy);
 
 	return 0;
 }
@@ -1248,6 +1255,7 @@ static struct cpufreq_driver intel_pstat
 	.flags		= CPUFREQ_CONST_LOOPS,
 	.verify		= intel_pstate_verify_policy,
 	.setpolicy	= intel_pstate_set_policy,
+	.resume		= intel_pstate_hwp_set_policy,
 	.get		= intel_pstate_get,
 	.init		= intel_pstate_cpu_init,
 	.stop_cpu	= intel_pstate_stop_cpu,
Index: linux-pm/drivers/cpufreq/cpufreq.c
===================================================================
--- linux-pm.orig/drivers/cpufreq/cpufreq.c
+++ linux-pm/drivers/cpufreq/cpufreq.c
@@ -1631,21 +1631,25 @@ void cpufreq_suspend(void)
 	if (!cpufreq_driver)
 		return;
 
-	if (!has_target())
+	if (!has_target() && !cpufreq_driver->suspend)
 		goto suspend;
 
 	pr_debug("%s: Suspending Governors\n", __func__);
 
 	for_each_active_policy(policy) {
-		down_write(&policy->rwsem);
-		ret = cpufreq_governor(policy, CPUFREQ_GOV_STOP);
-		up_write(&policy->rwsem);
-
-		if (ret)
-			pr_err("%s: Failed to stop governor for policy: %p\n",
-				__func__, policy);
-		else if (cpufreq_driver->suspend
-		    && cpufreq_driver->suspend(policy))
+		if (has_target()) {
+			down_write(&policy->rwsem);
+			ret = cpufreq_governor(policy, CPUFREQ_GOV_STOP);
+			up_write(&policy->rwsem);
+
+			if (ret) {
+				pr_err("%s: Failed to stop governor for policy: %p\n",
+					__func__, policy);
+				continue;
+			}
+		}
+
+		if (cpufreq_driver->suspend && cpufreq_driver->suspend(policy))
 			pr_err("%s: Failed to suspend driver: %p\n", __func__,
 				policy);
 	}
@@ -1670,7 +1674,7 @@ void cpufreq_resume(void)
 
 	cpufreq_suspended = false;
 
-	if (!has_target())
+	if (!has_target() && !cpufreq_driver->resume)
 		return;
 
 	pr_debug("%s: Resuming Governors\n", __func__);
@@ -1679,7 +1683,7 @@ void cpufreq_resume(void)
 		if (cpufreq_driver->resume && cpufreq_driver->resume(policy)) {
 			pr_err("%s: Failed to resume driver: %p\n", __func__,
 				policy);
-		} else {
+		} else if (has_target()) {
 			down_write(&policy->rwsem);
 			ret = cpufreq_start_governor(policy);
 			up_write(&policy->rwsem);