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

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Date:	Thu, 25 Oct 2012 12:03:34 +0530
From:	Viresh Kumar <viresh.kumar@...aro.org>
To:	rjw@...k.pl
Cc:	cpufreq@...r.kernel.org, linux-pm@...r.kernel.org,
	linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
	linaro-dev@...ts.linaro.org, patches@...aro.org,
	pdsw-power-team@....com, arvind.chauhan@....com,
	Viresh Kumar <viresh.kumar@...aro.org>
Subject: [RFC] cpufreq: Make sure target freq is within limits

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@...aro.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);
 
-- 
1.7.12.rc2.18.g61b472e


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