From 703cbaa601ff3fb554d1246c336ba727cc083ea0 Mon Sep 17 00:00:00 2001
From: Bo Yan <byan@nvidia.com>
Date: Tue, 23 Jan 2018 13:57:55 -0800
Subject: [PATCH] cpufreq: Skip cpufreq resume if it's not suspended
Git-commit: 703cbaa601ff3fb554d1246c336ba727cc083ea0
Patch-mainline: v4.16-rc1
References: bsc#1051510

cpufreq_resume can be called even without preceding cpufreq_suspend.
This can happen in following scenario:

    suspend_devices_and_enter
       --> dpm_suspend_start
          --> dpm_prepare
              --> device_prepare : this function errors out
          --> dpm_suspend: this is skipped due to dpm_prepare failure
                           this means cpufreq_suspend is skipped over
       --> goto Recover_platform, due to previous error
       --> goto Resume_devices
       --> dpm_resume_end
           --> dpm_resume
               --> cpufreq_resume

In case schedutil is used as frequency governor, cpufreq_resume will
eventually call sugov_start, which does following:

    memset(sg_cpu, 0, sizeof(*sg_cpu));
    ....

This effectively erases function pointer for frequency update, causing
crash later on. The function pointer would have been set correctly if
subsequent cpufreq_add_update_util_hook runs successfully, but that
function returns earlier because cpufreq_suspend was not called:

    if (WARN_ON(per_cpu(cpufreq_update_util_data, cpu)))
		return;

The fix is to check cpufreq_suspended first, if it's false, that means
cpufreq_suspend was not called in the first place, so do not resume
cpufreq.

Signed-off-by: Bo Yan <byan@nvidia.com>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
[ rjw: Dropped printing a message ]

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Acked-by: Takashi Iwai <tiwai@suse.de>

---
 drivers/cpufreq/cpufreq.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
index 421f318c0e66..de33ebf008ad 100644
--- a/drivers/cpufreq/cpufreq.c
+++ b/drivers/cpufreq/cpufreq.c
@@ -1686,6 +1686,9 @@ void cpufreq_resume(void)
 	if (!cpufreq_driver)
 		return;
 
+	if (unlikely(!cpufreq_suspended))
+		return;
+
 	cpufreq_suspended = false;
 
 	if (!has_target() && !cpufreq_driver->resume)
-- 
2.16.4