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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: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
This commit is contained in:
Viresh Kumar 2017-07-19 15:42:46 +05:30 committed by Rafael J. Wysocki
parent 768608a578
commit ed4676e254
3 changed files with 7 additions and 12 deletions
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8
drivers/cpufreq/cpufreq.c
View File

@ -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 {

2
drivers/cpufreq/cpufreq_governor.h
View File

@ -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, \

9
include/linux/cpufreq.h
View File

@ -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;
};