From 789ca243740de236a39146fc3d3bbaeb4d3ae0ba Mon Sep 17 00:00:00 2001 From: Preeti U Murthy Date: Mon, 29 Sep 2014 15:47:12 +0200 Subject: cpufreq: Allow stop CPU callback to be used by all cpufreq drivers Commit 367dc4aa932bfb3 ("cpufreq: Add stop CPU callback to cpufreq_driver interface") introduced the stop CPU callback for intel_pstate drivers. During the CPU_DOWN_PREPARE stage, this callback is invoked so that drivers can take some action on the pstate of the cpu before it is taken offline. This callback was assumed to be useful only for those drivers which have implemented the set_policy CPU callback because they have no other way to take action about the cpufreq of a CPU which is being hotplugged out except in the exit callback which is called very late in the offline process. The drivers which implement the target/target_index callbacks were expected to take care of requirements like the ones that commit 367dc4aa addresses in the GOV_STOP notification event. But there are disadvantages to restricting the usage of stop CPU callback to cpufreq drivers that implement the set_policy callbacks and who want to take explicit action on the setting the cpufreq during a hotplug operation. 1.GOV_STOP gets called for every CPU offline and drivers would usually want to take action when the last cpu in the policy->cpus mask is taken offline. As long as there is more than one cpu in the policy->cpus mask, cpufreq core itself makes sure that the freq for the other cpus in this mask is set according to the maximum load. This is sensible and drivers which implement the target_index callback would mostly not want to modify that. However the cpufreq core leaves a loose end when the cpu in the policy->cpus mask is the last one to go offline; it does nothing explicit to the frequency of the core. Drivers may need a way to take some action here and stop CPU callback mechanism is the best way to do it today. 2. We cannot implement driver specific actions in the GOV_STOP mechanism. So we will need another driver callback which is invoked from here which is unnecessary. Therefore this patch extends the usage of stop CPU callback to be used by all cpufreq drivers as long as they have this callback implemented and irrespective of whether they are set_policy/target_index drivers. The assumption is if the drivers find the GOV_STOP path to be a suitable way of implementing what they want to do with the freq of the cpu going offine,they will not implement the stop CPU callback at all. Signed-off-by: Preeti U Murthy Acked-by: Viresh Kumar Signed-off-by: Rafael J. Wysocki --- drivers/cpufreq/cpufreq.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'drivers/cpufreq') diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c index d9fdeddcef96..6463f35f8be8 100644 --- a/drivers/cpufreq/cpufreq.c +++ b/drivers/cpufreq/cpufreq.c @@ -1380,7 +1380,7 @@ static int __cpufreq_remove_dev_prepare(struct device *dev, if (!cpufreq_suspended) pr_debug("%s: policy Kobject moved to cpu: %d from: %d\n", __func__, new_cpu, cpu); - } else if (cpufreq_driver->stop_cpu && cpufreq_driver->setpolicy) { + } else if (cpufreq_driver->stop_cpu) { cpufreq_driver->stop_cpu(policy); } -- cgit v1.2.1