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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, Doug Smythies <dsmythies@telus.net>,
        Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>,
        Yu Chen <yu.c.chen@intel.com>,
        "Rafael J. Wysocki" <rafael.j.wysocki@intel.com>,
        Sasha Levin <alexander.levin@microsoft.com>
Subject: [PATCH 4.14 151/183] cpufreq: intel_pstate: Enable HWP during system resume on CPU0
Date:   Wed, 25 Apr 2018 12:36:11 +0200
Message-Id: <20180425103248.606860969@linuxfoundation.org>
In-Reply-To: <20180425103242.532713678@linuxfoundation.org>
References: <20180425103242.532713678@linuxfoundation.org>
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4.14-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Chen Yu <yu.c.chen@intel.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@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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 drivers/cpufreq/intel_pstate.c |    5 +++++
 1 file changed, 5 insertions(+)

--- a/drivers/cpufreq/intel_pstate.c
+++ b/drivers/cpufreq/intel_pstate.c
@@ -779,6 +779,8 @@ static int intel_pstate_hwp_save_state(s
 	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 cp
 
 	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);