Three 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.
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, or any other "static" governors.
Signed-off-by: MyungJoo Ham <myungjoo.ham@xxxxxxxxxxx>
Signed-off-by: Kyungmin Park <kyungmin.park@xxxxxxxxxxx>
---
Changes from v3:
- Bugfixes on simple-ondemand governor (divide by zero / overflow)
- Style fixes
- Give names to governors
---
drivers/base/power/devfreq.c | 85 ++++++++++++++++++++++++++++++++++++++++++
include/linux/devfreq.h | 5 ++
2 files changed, 90 insertions(+), 0 deletions(-)
diff --git a/drivers/base/power/devfreq.c b/drivers/base/power/devfreq.c
index aba9768..e5a73aa 100644
--- a/drivers/base/power/devfreq.c
+++ b/drivers/base/power/devfreq.c
@@ -395,3 +395,88 @@ static int __init devfreq_init(void)
return 0;
}
late_initcall(devfreq_init);
+
+static int devfreq_powersave_func(struct devfreq *df,
+ unsigned long *freq)
+{
+ *freq = 0; /* devfreq_do will run "ceiling" to 0 */
+ return 0;
+}
+
+struct devfreq_governor devfreq_powersave = {
+ .name = "powersave",
+ .get_target_freq = devfreq_powersave_func,
+};
+
+static int devfreq_performance_func(struct devfreq *df,
+ unsigned long *freq)
+{
+ *freq = UINT_MAX; /* devfreq_do will run "floor" */
+ return 0;
+}
+
+struct devfreq_governor devfreq_performance = {
+ .name = "performance",
+ .get_target_freq = devfreq_performance_func,
+};
+
+/* Constants for DevFreq-Simple-Ondemand (DFSO) */
+#define DFSO_UPTHRESHOLD (90)
+#define DFSO_DOWNDIFFERENCTIAL (5)
+static int devfreq_simple_ondemand_func(struct devfreq *df,
+ unsigned long *freq)
+{
+ struct devfreq_dev_status stat;
+ int err = df->profile->get_dev_status(df->dev, &stat);
+ unsigned long long a, b;
+
+ if (err)
+ return err;
+
+ /* Assume MAX if it is going to be divided by zero */
+ if (stat.total_time == 0) {
+ *freq = UINT_MAX;
+ return 0;
+ }
+
+ /* Prevent overflow */
+ if (stat.busy_time >= (1 << 24) || stat.total_time >= (1 << 24)) {
+ stat.busy_time >>= 7;
+ stat.total_time >>= 7;
+ }
+
+ /* Set MAX if it's busy enough */
+ if (stat.busy_time * 100 >
+ stat.total_time * DFSO_UPTHRESHOLD) {
+ *freq = UINT_MAX;
+ return 0;
+ }
+
+ /* Set MAX if we do not know the initial frequency */
+ if (stat.current_frequency == 0) {
+ *freq = UINT_MAX;
+ return 0;
+ }
+
+ /* Keep the current frequency */
+ if (stat.busy_time * 100 >
+ stat.total_time * (DFSO_UPTHRESHOLD - DFSO_DOWNDIFFERENCTIAL)) {
+ *freq = stat.current_frequency;
+ return 0;
+ }
+
+ /* Set the desired frequency based on the load */
+ a = stat.busy_time;
+ a *= stat.current_frequency;
+ b = div_u64(a, stat.total_time);
+ b *= 100;
+ b = div_u64(b, (DFSO_UPTHRESHOLD - DFSO_DOWNDIFFERENCTIAL / 2));
+ *freq = (unsigned long) b;
+
+ return 0;
+}
+
+struct devfreq_governor devfreq_simple_ondemand = {
+ .name = "simple_ondemand",
+ .get_target_freq = devfreq_simple_ondemand_func,
+};
diff --git a/include/linux/devfreq.h b/include/linux/devfreq.h
index 7c881cc..baa074c 100644
--- a/include/linux/devfreq.h
+++ b/include/linux/devfreq.h
@@ -84,6 +84,11 @@ extern int devfreq_add_device(struct device *dev,
extern int devfreq_remove_device(struct device *dev);
extern int devfreq_update(struct device *dev);
extern int devfreq_tickle_device(struct device *dev, unsigned long duration_ms);
+
+extern struct devfreq_governor devfreq_powersave;
+extern struct devfreq_governor devfreq_performance;
+extern struct devfreq_governor devfreq_simple_ondemand;
+
#else /* !CONFIG_PM_DEVFREQ */
static int devfreq_add_device(struct device *dev,
struct devfreq_dev_profile *profile,
--
1.7.4.1
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