linux-kernel - [PATCH 1/2] cpufreq: conservative: fix requested

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Message-ID: <1383888232-27049-1-git-send-email-chenxg@marvell.com>
Date:	Fri, 8 Nov 2013 13:23:51 +0800
From:	Xiaoguang Chen <chenxg@...vell.com>
To:	<rjw@...ysocki.net>, <viresh.kumar@...aro.org>,
	<cpufreq@...r.kernel.org>, <linux-pm@...r.kernel.org>,
	<linux-kernel@...r.kernel.org>
CC:	<chenxg@...vell.com>, <chenxg.marvell@...il.com>
Subject: [PATCH 1/2] cpufreq: conservative: fix requested_freq reduction issue

When decreasing frequency, requested_freq may be less than
freq_target, So requested_freq minus freq_target may be negative,
But reqested_freq's unit is unsigned int, then the negative result
will be one larger integer which may be even higher than
requested_freq.

This patch is to fix such issue. when result becomes negative,
set requested_freq as the min value of policy.

Signed-off-by: Xiaoguang Chen <chenxg@...vell.com>
Acked-by: Viresh Kumar <viresh.kumar@...aro.org>
---
 drivers/cpufreq/cpufreq_conservative.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/drivers/cpufreq/cpufreq_conservative.c b/drivers/cpufreq/cpufreq_conservative.c
index f62d822..218460f 100644
--- a/drivers/cpufreq/cpufreq_conservative.c
+++ b/drivers/cpufreq/cpufreq_conservative.c
@@ -80,13 +80,18 @@ static void cs_check_cpu(int cpu, unsigned int load)
 
 	/* Check for frequency decrease */
 	if (load < cs_tuners->down_threshold) {
+		unsigned int freq_target;
 		/*
 		 * if we cannot reduce the frequency anymore, break out early
 		 */
 		if (policy->cur == policy->min)
 			return;
 
-		dbs_info->requested_freq -= get_freq_target(cs_tuners, policy);
+		freq_target = get_freq_target(cs_tuners, policy);
+		if (dbs_info->requested_freq > freq_target)
+			dbs_info->requested_freq -= freq_target;
+		else
+			dbs_info->requested_freq = policy->min;
 
 		__cpufreq_driver_target(policy, dbs_info->requested_freq,
 				CPUFREQ_RELATION_L);
-- 
1.8.0

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