[RFC] cpufreq: Make sure target freq is within limits

Viresh Kumar viresh.kumar at linaro.org
Thu Oct 25 02:33:34 EDT 2012

Hi Rafael,

__cpufreq_driver_target() must not pass target frequency beyond the limits of
current policy.

Today most of cpufreq platform drivers are doing this check in their target
routines. Why not move it to __cpufreq_driver_target().

I wanted to get your opinion on this before making changes in all driver files.
That's why this is an RFC.

Signed-off-by: Viresh Kumar <viresh.kumar at linaro.org>
 drivers/cpufreq/cpufreq.c | 11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
index f552d5f..59264f1 100644
--- a/drivers/cpufreq/cpufreq.c
+++ b/drivers/cpufreq/cpufreq.c
@@ -1470,12 +1470,19 @@ int __cpufreq_driver_target(struct cpufreq_policy *policy,
 			    unsigned int relation)
 	int retval = -EINVAL;
+	unsigned int old_target_freq = target_freq;
 	if (cpufreq_disabled())
 		return -ENODEV;
-	pr_debug("target for CPU %u: %u kHz, relation %u\n", policy->cpu,
-		target_freq, relation);
+	/* Make sure that target_freq is within supported range */
+	if (target_freq > policy->max)
+		target_freq = policy->max;
+	if (target_freq < policy->min)
+		target_freq = policy->min;
+	pr_debug("target for CPU %u: %u kHz, relation %u, requested %u kHz\n",
+			policy->cpu, target_freq, relation, old_target_freq);
 	if (cpu_online(policy->cpu) && cpufreq_driver->target)
 		retval = cpufreq_driver->target(policy, target_freq, relation);

More information about the linux-arm-kernel mailing list