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 interger 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@marvell.com>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

diff --git a/drivers/cpufreq/cpufreq_conservative.c b/drivers/cpufreq/cpufreq_conservative.c
index f62d822048e62f0433c2b89f1b1fb5610b0493ff..218460fcd2e4f9294d24b84680f173f838c11332 100644 (file)
--- 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);