linux-kernel - [PATCH AUTOSEL for 4.14 140/161] cpufreq: intel_pstate: Enable HWP during system resume on CPU0

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Date:   Mon, 9 Apr 2018 00:21:48 +0000
From:   Sasha Levin <Alexander.Levin@...rosoft.com>
To:     "stable@...r.kernel.org" <stable@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
CC:     Chen Yu <yu.c.chen@...el.com>,
        "Rafael J . Wysocki" <rafael.j.wysocki@...el.com>,
        Sasha Levin <Alexander.Levin@...rosoft.com>
Subject: [PATCH AUTOSEL for 4.14 140/161] cpufreq: intel_pstate: Enable HWP
 during system resume on CPU0

From: Chen Yu <yu.c.chen@...el.com>

[ Upstream commit 70f6bf2a3b7e40c3f802b0ea837762a8bc6c1430 ]

When maxcpus=1 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@...us.net>
Suggested-by: Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>
Signed-off-by: Yu Chen <yu.c.chen@...el.com>
[ rjw: Subject/changelog, minor modifications ]
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
Signed-off-by: Sasha Levin <alexander.levin@...rosoft.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_policy *policy)
 	return 0;
 }
 
+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 *policy)
 
 	mutex_lock(&intel_pstate_limits_lock);
 
+	if (policy->cpu == 0)
+		intel_pstate_hwp_enable(all_cpu_data[policy->cpu]);
+
 	all_cpu_data[policy->cpu]->epp_policy = 0;
 	intel_pstate_hwp_set(policy->cpu);
 
-- 
2.15.1