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From:   Sasha Levin <Alexander.Levin@microsoft.com>
To:     "stable@vger.kernel.org" <stable@vger.kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
CC:     Chen Yu <yu.c.chen@intel.com>,
        "Rafael J . Wysocki" <rafael.j.wysocki@intel.com>,
        Sasha Levin <Alexander.Levin@microsoft.com>
Subject: [PATCH AUTOSEL for 4.15 166/189] cpufreq: intel_pstate: Enable HWP
 during system resume on CPU0
Thread-Topic: [PATCH AUTOSEL for 4.15 166/189] cpufreq: intel_pstate: Enable
 HWP during system resume on CPU0
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Date:   Mon, 9 Apr 2018 00:19:00 +0000
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From: Chen Yu <yu.c.chen@intel.com>

[ Upstream commit 70f6bf2a3b7e40c3f802b0ea837762a8bc6c1430 ]

When maxcpus=3D1 is in the kernel command line, the BP is responsible
for re-enabling the HWP - because currently only the APs invoke
intel_pstate_hwp_enable() during their online process - which might
put the system into unstable state after resume.

Fix this by enabling the HWP explicitly on BP during resume.

Reported-by: Doug Smythies <dsmythies@telus.net>
Suggested-by: Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>
Signed-off-by: Yu Chen <yu.c.chen@intel.com>
[ rjw: Subject/changelog, minor modifications ]
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
---
 drivers/cpufreq/intel_pstate.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/drivers/cpufreq/intel_pstate.c b/drivers/cpufreq/intel_pstate.=
c
index 93a0e88bef76..20226d4243f2 100644
--- a/drivers/cpufreq/intel_pstate.c
+++ b/drivers/cpufreq/intel_pstate.c
@@ -779,6 +779,8 @@ static int intel_pstate_hwp_save_state(struct cpufreq_p=
olicy *policy)
 	return 0;
 }
=20
+static void intel_pstate_hwp_enable(struct cpudata *cpudata);
+
 static int intel_pstate_resume(struct cpufreq_policy *policy)
 {
 	if (!hwp_active)
@@ -786,6 +788,9 @@ static int intel_pstate_resume(struct cpufreq_policy *p=
olicy)
=20
 	mutex_lock(&intel_pstate_limits_lock);
=20
+	if (policy->cpu =3D=3D 0)
+		intel_pstate_hwp_enable(all_cpu_data[policy->cpu]);
+
 	all_cpu_data[policy->cpu]->epp_policy =3D 0;
 	intel_pstate_hwp_set(policy->cpu);
=20
--=20
2.15.1