PM / devfreq: Add PM QoS support

Register notifiers with the PM QoS framework in order to respond to
requests for DEV_PM_QOS_MIN_FREQUENCY and DEV_PM_QOS_MAX_FREQUENCY.

No notifiers are added by this patch but PM QoS constraints can be
imposed externally (for example from other devices).
Signed-off-by: Leonard Crestez <leonard.crestez@nxp.com>
Acked-by: Chanwoo Choi <cw00.choi@samsung.com>
Reviewed-by: Matthias Kaehlcke <mka@chromium.org>
Tested-by: Matthias Kaehlcke <mka@chromium.org>
Signed-off-by: Chanwoo Choi <cw00.choi@samsung.com>

drivers/devfreq/devfreq.c

@@ -24,11 +24,14 @@
 #include <linux/printk.h>
 #include <linux/hrtimer.h>
 #include <linux/of.h>
+#include <linux/pm_qos.h>
 #include "governor.h"
 
 #define CREATE_TRACE_POINTS
 #include <trace/events/devfreq.h>
 
+#define HZ_PER_KHZ	1000
+
 static struct class *devfreq_class;
 
 /*
@@ -111,6 +114,7 @@ static void get_freq_range(struct devfreq *devfreq,
 			   unsigned long *max_freq)
 {
 	unsigned long *freq_table = devfreq->profile->freq_table;
+	s32 qos_min_freq, qos_max_freq;
 
 	lockdep_assert_held(&devfreq->lock);
 
@@ -127,6 +131,16 @@ static void get_freq_range(struct devfreq *devfreq,
 		*max_freq = freq_table[0];
 	}
 
+	/* Apply constraints from PM QoS */
+	qos_min_freq = dev_pm_qos_read_value(devfreq->dev.parent,
+					     DEV_PM_QOS_MIN_FREQUENCY);
+	qos_max_freq = dev_pm_qos_read_value(devfreq->dev.parent,
+					     DEV_PM_QOS_MAX_FREQUENCY);
+	*min_freq = max(*min_freq, (unsigned long)HZ_PER_KHZ * qos_min_freq);
+	if (qos_max_freq != PM_QOS_MAX_FREQUENCY_DEFAULT_VALUE)
+		*max_freq = min(*max_freq,
+				(unsigned long)HZ_PER_KHZ * qos_max_freq);
+
 	/* Apply constraints from sysfs */
 	*min_freq = max(*min_freq, devfreq->min_freq);
 	*max_freq = min(*max_freq, devfreq->max_freq);
@@ -626,6 +640,45 @@ static int devfreq_notifier_call(struct notifier_block *nb, unsigned long type,
 	return NOTIFY_OK;
 }
 
+/**
+ * qos_notifier_call() - Common handler for QoS constraints.
+ * @devfreq:    the devfreq instance.
+ */
+static int qos_notifier_call(struct devfreq *devfreq)
+{
+	int err;
+
+	mutex_lock(&devfreq->lock);
+	err = update_devfreq(devfreq);
+	mutex_unlock(&devfreq->lock);
+	if (err)
+		dev_err(devfreq->dev.parent,
+			"failed to update frequency from PM QoS (%d)\n",
+			err);
+
+	return NOTIFY_OK;
+}
+
+/**
+ * qos_min_notifier_call() - Callback for QoS min_freq changes.
+ * @nb:		Should be devfreq->nb_min
+ */
+static int qos_min_notifier_call(struct notifier_block *nb,
+					 unsigned long val, void *ptr)
+{
+	return qos_notifier_call(container_of(nb, struct devfreq, nb_min));
+}
+
+/**
+ * qos_max_notifier_call() - Callback for QoS max_freq changes.
+ * @nb:		Should be devfreq->nb_max
+ */
+static int qos_max_notifier_call(struct notifier_block *nb,
+					 unsigned long val, void *ptr)
+{
+	return qos_notifier_call(container_of(nb, struct devfreq, nb_max));
+}
+
 /**
  * devfreq_dev_release() - Callback for struct device to release the device.
  * @dev:	the devfreq device
@@ -635,11 +688,23 @@ static int devfreq_notifier_call(struct notifier_block *nb, unsigned long type,
 static void devfreq_dev_release(struct device *dev)
 {
 	struct devfreq *devfreq = to_devfreq(dev);
+	int err;
 
 	mutex_lock(&devfreq_list_lock);
 	list_del(&devfreq->node);
 	mutex_unlock(&devfreq_list_lock);
 
+	err = dev_pm_qos_remove_notifier(devfreq->dev.parent, &devfreq->nb_max,
+					 DEV_PM_QOS_MAX_FREQUENCY);
+	if (err && err != -ENOENT)
+		dev_warn(dev->parent,
+			"Failed to remove max_freq notifier: %d\n", err);
+	err = dev_pm_qos_remove_notifier(devfreq->dev.parent, &devfreq->nb_min,
+					 DEV_PM_QOS_MIN_FREQUENCY);
+	if (err && err != -ENOENT)
+		dev_warn(dev->parent,
+			"Failed to remove min_freq notifier: %d\n", err);
+
 	if (devfreq->profile->exit)
 		devfreq->profile->exit(devfreq->dev.parent);
 
@@ -762,6 +827,18 @@ struct devfreq *devfreq_add_device(struct device *dev,
 
 	mutex_unlock(&devfreq->lock);
 
+	devfreq->nb_min.notifier_call = qos_min_notifier_call;
+	err = dev_pm_qos_add_notifier(devfreq->dev.parent, &devfreq->nb_min,
+				      DEV_PM_QOS_MIN_FREQUENCY);
+	if (err)
+		goto err_devfreq;
+
+	devfreq->nb_max.notifier_call = qos_max_notifier_call;
+	err = dev_pm_qos_add_notifier(devfreq->dev.parent, &devfreq->nb_max,
+				      DEV_PM_QOS_MAX_FREQUENCY);
+	if (err)
+		goto err_devfreq;
+
 	mutex_lock(&devfreq_list_lock);
 
 	governor = try_then_request_governor(devfreq->governor_name);

include/linux/devfreq.h

@@ -136,6 +136,8 @@ struct devfreq_dev_profile {
  * @time_in_state:	Statistics of devfreq states
  * @last_stat_updated:	The last time stat updated
  * @transition_notifier_list: list head of DEVFREQ_TRANSITION_NOTIFIER notifier
+ * @nb_min:		Notifier block for DEV_PM_QOS_MIN_FREQUENCY
+ * @nb_max:		Notifier block for DEV_PM_QOS_MAX_FREQUENCY
  *
  * This structure stores the devfreq information for a give device.
  *
@@ -178,6 +180,9 @@ struct devfreq {
 	unsigned long last_stat_updated;
 
 	struct srcu_notifier_head transition_notifier_list;
+
+	struct notifier_block nb_min;
+	struct notifier_block nb_max;
 };
 
 struct devfreq_freqs {