PM / devfreq: Add basic governors

Four cpufreq-like governors are provided as examples.

powersave: use the lowest frequency possible. The user (device) should
set the polling_ms as 0 because polling is useless for this governor.

performance: use the highest freqeuncy possible. The user (device)
should set the polling_ms as 0 because polling is useless for this
governor.

userspace: use the user specified frequency stored at
devfreq.user_set_freq. With sysfs support in the following patch, a user
may set the value with the sysfs interface.

simple_ondemand: simplified version of cpufreq's ondemand governor.

When a user updates OPP entries (enable/disable/add), OPP framework
automatically notifies devfreq to update operating frequency
accordingly. Thus, devfreq users (device drivers) do not need to update
devfreq manually with OPP entry updates or set polling_ms for powersave
, performance, userspace, or any other "static" governors.

Note that these are given only as basic examples for governors and any
devices with devfreq may implement their own governors with the drivers
and use them.

Signed-off-by: MyungJoo Ham <myungjoo.ham@samsung.com>
Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>
Reviewed-by: Mike Turquette <mturquette@ti.com>
Acked-by: Kevin Hilman <khilman@ti.com>
Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>

1 files changed, 35 insertions, 0 deletions

diff --git a/include/linux/devfreq.h b/include/linux/devfreq.h
index b3be3d3cbaa7..afb94583960c 100644
--- a/include/linux/devfreq.h
+++ b/include/linux/devfreq.h
@@ -166,6 +166,36 @@ extern int devfreq_register_opp_notifier(struct device *dev,
 extern int devfreq_unregister_opp_notifier(struct device *dev,
                                            struct devfreq *devfreq);
 
+#ifdef CONFIG_DEVFREQ_GOV_POWERSAVE
+extern const struct devfreq_governor devfreq_powersave;
+#endif
+#ifdef CONFIG_DEVFREQ_GOV_PERFORMANCE
+extern const struct devfreq_governor devfreq_performance;
+#endif
+#ifdef CONFIG_DEVFREQ_GOV_USERSPACE
+extern const struct devfreq_governor devfreq_userspace;
+#endif
+#ifdef CONFIG_DEVFREQ_GOV_SIMPLE_ONDEMAND
+extern const struct devfreq_governor devfreq_simple_ondemand;
+/**
+ * struct devfreq_simple_ondemand_data - void *data fed to struct devfreq
+ *      and devfreq_add_device
+ * @ upthreshold        If the load is over this value, the frequency jumps.
+ *                      Specify 0 to use the default. Valid value = 0 to 100.
+ * @ downdifferential   If the load is under upthreshold - downdifferential,
+ *                      the governor may consider slowing the frequency down.
+ *                      Specify 0 to use the default. Valid value = 0 to 100.
+ *                      downdifferential < upthreshold must hold.
+ *
+ * If the fed devfreq_simple_ondemand_data pointer is NULL to the governor,
+ * the governor uses the default values.
+ */
+struct devfreq_simple_ondemand_data {
+        unsigned int upthreshold;
+        unsigned int downdifferential;
+};
+#endif
+
 #else /* !CONFIG_PM_DEVFREQ */
 static struct devfreq *devfreq_add_device(struct device *dev,
                                           struct devfreq_dev_profile *profile,
@@ -198,6 +228,11 @@ static int devfreq_unregister_opp_notifier(struct device *dev,
         return -EINVAL;
 }
 
+#define devfreq_powersave       NULL
+#define devfreq_performance     NULL
+#define devfreq_userspace       NULL
+#define devfreq_simple_ondemand NULL
+
 #endif /* CONFIG_PM_DEVFREQ */
 
 #endif /* __LINUX_DEVFREQ_H__ */