PM / devfreq: Add cpu based scaling support to passive governor

Many CPU architectures have caches that can scale independent of the
CPUs. Frequency scaling of the caches is necessary to make sure that the
cache is not a performance bottleneck that leads to poor performance and
power. The same idea applies for RAM/DDR.

To achieve this, this patch adds support for cpu based scaling to the
passive governor. This is accomplished by taking the current frequency
of each CPU frequency domain and then adjust the frequency of the cache
(or any devfreq device) based on the frequency of the CPUs. It listens
to CPU frequency transition notifiers to keep itself up to date on the
current CPU frequency.

To decide the frequency of the device, the governor does one of the
following:
* Derives the optimal devfreq device opp from required-opps property of
  the parent cpu opp_table.

* Scales the device frequency in proportion to the CPU frequency. So, if
  the CPUs are running at their max frequency, the device runs at its
  max frequency. If the CPUs are running at their min frequency, the
  device runs at its min frequency. It is interpolated for frequencies
  in between.

Tested-by: Chen-Yu Tsai <wenst@chromium.org>
Tested-by: Johnson Wang <johnson.wang@mediatek.com>
Signed-off-by: Saravana Kannan <skannan@codeaurora.org>
[Sibi: Integrated cpu-freqmap governor into passive_governor]
Signed-off-by: Sibi Sankar <sibis@codeaurora.org>
[Chanwoo: Fix conflict with latest code and cleanup code]
Signed-off-by: Chanwoo Choi <cw00.choi@samsung.com>

1 files changed, 15 insertions, 2 deletions

diff --git a/include/linux/devfreq.h b/include/linux/devfreq.h
index 142474b4af96..b1e4a6f796ce 100644
--- a/include/linux/devfreq.h
+++ b/include/linux/devfreq.h
@@ -38,6 +38,7 @@ enum devfreq_timer {
 
 struct devfreq;
 struct devfreq_governor;
+struct devfreq_cpu_data;
 struct thermal_cooling_device;
 
 /**
@@ -288,6 +289,11 @@ struct devfreq_simple_ondemand_data {
 #endif
 
 #if IS_ENABLED(CONFIG_DEVFREQ_GOV_PASSIVE)
+enum devfreq_parent_dev_type {
+	DEVFREQ_PARENT_DEV,
+	CPUFREQ_PARENT_DEV,
+};
+
 /**
  * struct devfreq_passive_data - ``void *data`` fed to struct devfreq
  *	and devfreq_add_device
@@ -299,8 +305,11 @@ struct devfreq_simple_ondemand_data {
  *			using governors except for passive governor.
  *			If the devfreq device has the specific method to decide
  *			the next frequency, should use this callback.
- * @this:	the devfreq instance of own device.
- * @nb:		the notifier block for DEVFREQ_TRANSITION_NOTIFIER list
+ * @parent_type:	the parent type of the device.
+ * @this:		the devfreq instance of own device.
+ * @nb:			the notifier block for DEVFREQ_TRANSITION_NOTIFIER or
+ *			CPUFREQ_TRANSITION_NOTIFIER list.
+ * @parent_cpu_data:	the state min/max/current frequency of all online cpu's.
  *
  * The devfreq_passive_data have to set the devfreq instance of parent
  * device with governors except for the passive governor. But, don't need to
@@ -314,9 +323,13 @@ struct devfreq_passive_data {
 	/* Optional callback to decide the next frequency of passvice device */
 	int (*get_target_freq)(struct devfreq *this, unsigned long *freq);
 
+	/* Should set the type of parent device */
+	enum devfreq_parent_dev_type parent_type;
+
 	/* For passive governor's internal use. Don't need to set them */
 	struct devfreq *this;
 	struct notifier_block nb;
+	struct devfreq_cpu_data *parent_cpu_data[NR_CPUS];
 };
 #endif