linux-kernel - [PATCH V3] cpufreq: reinitialize new policy min/max when writing scaling_(max|min)

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Date:   Wed, 30 May 2018 15:56:47 +0800
From:   Kevin Wangtao <kevin.wangtao@...ilicon.com>
To:     <rjw@...ysocki.net>, <viresh.kumar@...aro.org>
CC:     <linux-pm@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <gengyanping@...ilicon.com>, <sunzhaosheng@...ilicon.com>,
        Kevin Wangtao <kevin.wangtao@...ilicon.com>
Subject: [PATCH V3] cpufreq: reinitialize new policy min/max when writing scaling_(max|min)_freq

consider such situation, current user_policy.min is 1000000,
current user_policy.max is 1200000, in cpufreq_set_policy,
other driver may update policy.min to 1200000, policy.max to
1300000. After that, If we input "echo 1300000 > scaling_min_freq",
then user_policy.min will be 1300000, and user_policy.max is
still 1200000, because the input value is checked with policy.max
not user_policy.max. if we get all related cpus offline and
online again, it will cause cpufreq_init_policy fail because
user_policy.min is higher than user_policy.max.

The solution is when user space tries to write scaling_(max|min)_freq,
the min/max of new_policy should be reinitialized with min/max
of user_policy, like what cpufreq_update_policy does.

Signed-off-by: Kevin Wangtao <kevin.wangtao@...ilicon.com>
---
 drivers/cpufreq/cpufreq.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
index b79c532..a970113 100644
--- a/drivers/cpufreq/cpufreq.c
+++ b/drivers/cpufreq/cpufreq.c
@@ -697,6 +697,9 @@ static ssize_t store_##file_name					\
 	struct cpufreq_policy new_policy;				\
 									\
 	memcpy(&new_policy, policy, sizeof(*policy));			\
+	/* Initialized with user_policy to keep consistency */		\
+	new_policy.min = policy->user_policy.min;			\
+	new_policy.max = policy->user_policy.max;			\
 									\
 	ret = sscanf(buf, "%u", &new_policy.object);			\
 	if (ret != 1)							\
-- 
2.8.1