[CPUFREQ] Fix ondemand to not request targets outside policy limits

Nagananda.Chumbalkar@hp.com · Dave Jones · commit 1dbf58881f30 · 2010-01-13T10:55:16.000-05:00
Dominik said:
target_freq cannot be below policy-&gt;min or above policy-&gt;max.
If it were, the whole cpufreq subsystem is broken.

But (answer):
I think the "ondemand" governor can ask for a target frequency that is
below policy-&gt;min.
...
A patch such as below may be needed to sanitize the target frequency
requested by "ondemand". The "conservative" governor already has this check:

Signed-off-by: Thomas Renninger &lt;trenn@suse.de&gt;
Signed-off-by: Dave Jones &lt;davej@redhat.com&gt;

# diff -bur x/drivers/cpufreq/cpufreq_ondemand.c.orig y/drivers/cpufreq/cpufreq_ondemand.c
diff --git a/drivers/cpufreq/cpufreq_ondemand.c b/drivers/cpufreq/cpufreq_ondemand.c
@@ -554,6 +554,9 @@ static void dbs_check_cpu(struct cpu_dbs_info_s *this_dbs_info)
 				(dbs_tuners_ins.up_threshold -
 				 dbs_tuners_ins.down_differential);
 
+		if (freq_next < policy->min)
+			freq_next = policy->min;
+
 		if (!dbs_tuners_ins.powersave_bias) {
 			__cpufreq_driver_target(policy, freq_next,
 					CPUFREQ_RELATION_L);
