Commit ed4676e2 authored by Viresh Kumar's avatar Viresh Kumar Committed by Rafael J. Wysocki
Browse files

cpufreq: Replace "max_transition_latency" with "dynamic_switching" 



There is no limitation in the ondemand or conservative governors which
disallow the transition_latency to be greater than 10 ms.

The max_transition_latency field is rather used to disallow automatic
dynamic frequency switching for platforms which didn't wanted these
governors to run.

Replace max_transition_latency with a boolean (dynamic_switching) and
check for transition_latency == CPUFREQ_ETERNAL along with that. This
makes it pretty straight forward to read/understand now.

Signed-off-by: default avatarViresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: default avatarRafael J. Wysocki <rafael.j.wysocki@intel.com>
parent 768608a5

drivers/cpufreq/cpufreq.c

+4 −4
Original line number Diff line number Diff line
@@ -2003,13 +2003,13 @@ static int cpufreq_init_governor(struct cpufreq_policy *policy) 
	if (!policy->governor)

		return -EINVAL;



	if (policy->governor->max_transition_latency &&

	    policy->cpuinfo.transition_latency >

	    policy->governor->max_transition_latency) {

	/* Platform doesn't want dynamic frequency switching ? */

	if (policy->governor->dynamic_switching &&

	    policy->cpuinfo.transition_latency == CPUFREQ_ETERNAL) {

		struct cpufreq_governor *gov = cpufreq_fallback_governor();



		if (gov) {

			pr_warn("%s governor failed, too long transition latency of HW, fallback to %s governor\n",

			pr_warn("Transition latency set to CPUFREQ_ETERNAL, can't use %s governor. Fallback to %s governor\n",

				policy->governor->name, gov->name);

			policy->governor = gov;

		} else {

drivers/cpufreq/cpufreq_governor.h

+1 −1
Original line number Diff line number Diff line
@@ -159,7 +159,7 @@ void cpufreq_dbs_governor_limits(struct cpufreq_policy *policy); 
#define CPUFREQ_DBS_GOVERNOR_INITIALIZER(_name_)			\

	{								\

		.name = _name_,						\

		.max_transition_latency	= TRANSITION_LATENCY_LIMIT,	\

		.dynamic_switching = true,				\

		.owner = THIS_MODULE,					\

		.init = cpufreq_dbs_governor_init,			\

		.exit = cpufreq_dbs_governor_exit,			\

include/linux/cpufreq.h

+2 −7
Original line number Diff line number Diff line
@@ -487,12 +487,8 @@ static inline unsigned long cpufreq_scale(unsigned long old, u_int div, 
 * polling frequency is 1000 times the transition latency of the processor. The

 * ondemand governor will work on any processor with transition latency <= 10ms,

 * using appropriate sampling rate.

 *

 * For CPUs with transition latency > 10ms (mostly drivers with CPUFREQ_ETERNAL)

 * the ondemand governor will not work. All times here are in us (microseconds).

 */

#define LATENCY_MULTIPLIER		(1000)

#define TRANSITION_LATENCY_LIMIT	(10 * 1000 * 1000)



struct cpufreq_governor {

	char	name[CPUFREQ_NAME_LEN];
@@ -505,9 +501,8 @@ struct cpufreq_governor { 
					 char *buf);

	int	(*store_setspeed)	(struct cpufreq_policy *policy,

					 unsigned int freq);

	unsigned int max_transition_latency; /* HW must be able to switch to

			next freq faster than this value in nano secs or we

			will fallback to performance governor */

	/* For governors which change frequency dynamically by themselves */

	bool			dynamic_switching;

	struct list_head	governor_list;

	struct module		*owner;

};

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