[PATCH v6 2/2] PM / devfreq: Add governor attribute flag for specifc sysfs nodes

[Chanwoo Choi]

DEVFREQ supports the default governors like performance, simple_ondemand and
also allows the devfreq driver to add their own governor like tegra30-devfreq.c
according to their requirement. In result, some sysfs attributes are useful
or not useful. Prior to that the user can access all sysfs attributes
regardless of the available attributes.

So, clarify the access permission of sysfs attributes according to governor.
When adding the devfreq governor, can specify the available attribute
information by using DEVFREQ_GOV_ATTR_* constant variable. The user can
read or write the sysfs attributes in accordance to the specified attributes.

When adding the governor, can add the following attributes
according to the governor feature.

[Definition for speific sysfs attributes]
- DEVFREQ_GOV_ATTR_POLLING_INTERVAL to update polling interval for timer.
  : /sys/class/devfreq/[devfreq dev name]/polling_interval
- DEVFREQ_GOV_ATTR_TIMER to change the type of timer on either deferrable
  or dealyed timer.
  : /sys/class/devfreq/[devfreq dev name]/timer

And all devfreq governors have to support the following common attributes.
The common attributes are added to devfreq class by default.
- governor
- available_governors
- available_frequencies
- cur_freq
- target_freq
- min_freq
- max_freq
- trans_stat

[Table of governor attribute flags for devfreq governors]
------------------------------------------------------------------------------
                      | simple    | perfor | power | user | passive | tegra30
		      | ondemand  | mance  | save  | space|         |
------------------------------------------------------------------------------
governor              | O         | O      | O     | O    | O       | O
available_governors   | O         | O      | O     | O    | O       | O
available_frequencies | O         | O      | O     | O    | O       | O
cur_freq              | O         | O      | O     | O    | O       | O
target_freq           | O         | O      | O     | O    | O       | O
min_freq              | O         | O      | O     | O    | O       | O
max_freq              | O         | O      | O     | O    | O       | O
trans_stat            | O         | O      | O     | O    | O       | O
                      --------------------------------------------------------
polling_interval      | O         | X      | X     | X    | X       | O
timer                 | O         | X      | X     | X    | X       | X
------------------------------------------------------------------------------

Reviewed-by: Dmitry Osipenko <digetx@xxxxxxxxx>
Tested-by: Dmitry Osipenko <digetx@xxxxxxxxx>
Signed-off-by: Chanwoo Choi <cw00.choi@xxxxxxxxxxx>
---
 Documentation/ABI/testing/sysfs-class-devfreq |  54 +++---
 drivers/devfreq/devfreq.c                     | 162 ++++++++++++------
 drivers/devfreq/governor.h                    |  12 ++
 drivers/devfreq/governor_simpleondemand.c     |   2 +
 drivers/devfreq/tegra30-devfreq.c             |   1 +
 5 files changed, 159 insertions(+), 72 deletions(-)

diff --git a/Documentation/ABI/testing/sysfs-class-devfreq b/Documentation/ABI/testing/sysfs-class-devfreq
index deefffb3bbe4..67af3f31e17c 100644
--- a/Documentation/ABI/testing/sysfs-class-devfreq
+++ b/Documentation/ABI/testing/sysfs-class-devfreq
@@ -37,20 +37,6 @@ Description:
 		The /sys/class/devfreq/.../target_freq shows the next governor
 		predicted target frequency of the corresponding devfreq object.
 
-What:		/sys/class/devfreq/.../polling_interval
-Date:		September 2011
-Contact:	MyungJoo Ham <myungjoo.ham@xxxxxxxxxxx>
-Description:
-		The /sys/class/devfreq/.../polling_interval shows and sets
-		the requested polling interval of the corresponding devfreq
-		object. The values are represented in ms. If the value is
-		less than 1 jiffy, it is considered to be 0, which means
-		no polling. This value is meaningless if the governor is
-		not polling; thus. If the governor is not using
-		devfreq-provided central polling
-		(/sys/class/devfreq/.../central_polling is 0), this value
-		may be useless.
-
 What:		/sys/class/devfreq/.../trans_stat
 Date:		October 2012
 Contact:	MyungJoo Ham <myungjoo.ham@xxxxxxxxxxx>
@@ -65,14 +51,6 @@ Description:
 		as following:
 			echo 0 > /sys/class/devfreq/.../trans_stat
 
-What:		/sys/class/devfreq/.../userspace/set_freq
-Date:		September 2011
-Contact:	MyungJoo Ham <myungjoo.ham@xxxxxxxxxxx>
-Description:
-		The /sys/class/devfreq/.../userspace/set_freq shows and
-		sets the requested frequency for the devfreq object if
-		userspace governor is in effect.
-
 What:		/sys/class/devfreq/.../available_frequencies
 Date:		October 2012
 Contact:	Nishanth Menon <nm@xxxxxx>
@@ -109,6 +87,35 @@ Description:
 		The max_freq overrides min_freq because max_freq may be
 		used to throttle devices to avoid overheating.
 
+What:		/sys/class/devfreq/.../polling_interval
+Date:		September 2011
+Contact:	MyungJoo Ham <myungjoo.ham@xxxxxxxxxxx>
+Description:
+		The /sys/class/devfreq/.../polling_interval shows and sets
+		the requested polling interval of the corresponding devfreq
+		object. The values are represented in ms. If the value is
+		less than 1 jiffy, it is considered to be 0, which means
+		no polling. This value is meaningless if the governor is
+		not polling; thus. If the governor is not using
+		devfreq-provided central polling
+		(/sys/class/devfreq/.../central_polling is 0), this value
+		may be useless.
+
+		A list of governors that support the node:
+		- simple_ondmenad
+		- tegra_actmon
+
+What:		/sys/class/devfreq/.../userspace/set_freq
+Date:		September 2011
+Contact:	MyungJoo Ham <myungjoo.ham@xxxxxxxxxxx>
+Description:
+		The /sys/class/devfreq/.../userspace/set_freq shows and
+		sets the requested frequency for the devfreq object if
+		userspace governor is in effect.
+
+		A list of governors that support the node:
+		- userspace
+
 What:		/sys/class/devfreq/.../timer
 Date:		July 2020
 Contact:	Chanwoo Choi <cw00.choi@xxxxxxxxxxx>
@@ -120,3 +127,6 @@ Description:
 		as following:
 			echo deferrable > /sys/class/devfreq/.../timer
 			echo delayed > /sys/class/devfreq/.../timer
+
+		A list of governors that support the node:
+		- simple_ondemand
diff --git a/drivers/devfreq/devfreq.c b/drivers/devfreq/devfreq.c
index a862acfe987e..02cfc6552913 100644
--- a/drivers/devfreq/devfreq.c
+++ b/drivers/devfreq/devfreq.c
@@ -32,6 +32,7 @@
 #include <trace/events/devfreq.h>
 
 #define IS_SUPPORTED_FLAG(f, name) ((f & DEVFREQ_GOV_FLAG_##name) ? true : false)
+#define IS_SUPPORTED_ATTR(f, name) ((f & DEVFREQ_GOV_ATTR_##name) ? true : false)
 #define HZ_PER_KHZ	1000
 
 static struct class *devfreq_class;
@@ -760,6 +761,11 @@ static void devfreq_dev_release(struct device *dev)
 	kfree(devfreq);
 }
 
+static void create_sysfs_files(struct devfreq *devfreq,
+				const struct devfreq_governor *gov);
+static void remove_sysfs_files(struct devfreq *devfreq,
+				const struct devfreq_governor *gov);
+
 /**
  * devfreq_add_device() - Add devfreq feature to the device
  * @dev:	the device to add devfreq feature.
@@ -917,6 +923,7 @@ struct devfreq *devfreq_add_device(struct device *dev,
 			__func__);
 		goto err_init;
 	}
+	create_sysfs_files(devfreq, devfreq->governor);
 
 	list_add(&devfreq->node, &devfreq_list);
 
@@ -947,9 +954,12 @@ int devfreq_remove_device(struct devfreq *devfreq)
 	if (!devfreq)
 		return -EINVAL;
 
-	if (devfreq->governor)
+	if (devfreq->governor) {
 		devfreq->governor->event_handler(devfreq,
 						 DEVFREQ_GOV_STOP, NULL);
+		remove_sysfs_files(devfreq, devfreq->governor);
+	}
+
 	device_unregister(&devfreq->dev);
 
 	return 0;
@@ -1378,13 +1388,22 @@ static ssize_t governor_store(struct device *dev, struct device_attribute *attr,
 		goto out;
 	}
 
+	/*
+	 * Stop the current governor and remove the specific sysfs files
+	 * which depend on current governor.
+	 */
 	ret = df->governor->event_handler(df, DEVFREQ_GOV_STOP, NULL);
 	if (ret) {
 		dev_warn(dev, "%s: Governor %s not stopped(%d)\n",
 			 __func__, df->governor->name, ret);
 		goto out;
 	}
+	remove_sysfs_files(df, df->governor);
 
+	/*
+	 * Start the new governor and create the specific sysfs files
+	 * which depend on the new governor.
+	 */
 	prev_governor = df->governor;
 	df->governor = governor;
 	strncpy(df->governor_name, governor->name, DEVFREQ_NAME_LEN);
@@ -1392,6 +1411,8 @@ static ssize_t governor_store(struct device *dev, struct device_attribute *attr,
 	if (ret) {
 		dev_warn(dev, "%s: Governor %s not started(%d)\n",
 			 __func__, df->governor->name, ret);
+
+		/* Restore previous governor */
 		df->governor = prev_governor;
 		strncpy(df->governor_name, prev_governor->name,
 			DEVFREQ_NAME_LEN);
@@ -1401,8 +1422,16 @@ static ssize_t governor_store(struct device *dev, struct device_attribute *attr,
 				"%s: reverting to Governor %s failed (%d)\n",
 				__func__, df->governor_name, ret);
 			df->governor = NULL;
+			goto out;
 		}
 	}
+
+	/*
+	 * Create the sysfs files for the new governor. But if failed to start
+	 * the new governor, restore the sysfs files of previous governor.
+	 */
+	create_sysfs_files(df, df->governor);
+
 out:
 	mutex_unlock(&devfreq_list_lock);
 
@@ -1484,39 +1513,6 @@ static ssize_t target_freq_show(struct device *dev,
 }
 static DEVICE_ATTR_RO(target_freq);
 
-static ssize_t polling_interval_show(struct device *dev,
-				     struct device_attribute *attr, char *buf)
-{
-	struct devfreq *df = to_devfreq(dev);
-
-	if (!df->profile)
-		return -EINVAL;
-
-	return sprintf(buf, "%d\n", df->profile->polling_ms);
-}
-
-static ssize_t polling_interval_store(struct device *dev,
-				      struct device_attribute *attr,
-				      const char *buf, size_t count)
-{
-	struct devfreq *df = to_devfreq(dev);
-	unsigned int value;
-	int ret;
-
-	if (!df->governor)
-		return -EINVAL;
-
-	ret = sscanf(buf, "%u", &value);
-	if (ret != 1)
-		return -EINVAL;
-
-	df->governor->event_handler(df, DEVFREQ_GOV_UPDATE_INTERVAL, &value);
-	ret = count;
-
-	return ret;
-}
-static DEVICE_ATTR_RW(polling_interval);
-
 static ssize_t min_freq_store(struct device *dev, struct device_attribute *attr,
 			      const char *buf, size_t count)
 {
@@ -1724,6 +1720,53 @@ static ssize_t trans_stat_store(struct device *dev,
 }
 static DEVICE_ATTR_RW(trans_stat);
 
+static struct attribute *devfreq_attrs[] = {
+	&dev_attr_name.attr,
+	&dev_attr_governor.attr,
+	&dev_attr_available_governors.attr,
+	&dev_attr_cur_freq.attr,
+	&dev_attr_available_frequencies.attr,
+	&dev_attr_target_freq.attr,
+	&dev_attr_min_freq.attr,
+	&dev_attr_max_freq.attr,
+	&dev_attr_trans_stat.attr,
+	NULL,
+};
+ATTRIBUTE_GROUPS(devfreq);
+
+static ssize_t polling_interval_show(struct device *dev,
+				     struct device_attribute *attr, char *buf)
+{
+	struct devfreq *df = to_devfreq(dev);
+
+	if (!df->profile)
+		return -EINVAL;
+
+	return sprintf(buf, "%d\n", df->profile->polling_ms);
+}
+
+static ssize_t polling_interval_store(struct device *dev,
+				      struct device_attribute *attr,
+				      const char *buf, size_t count)
+{
+	struct devfreq *df = to_devfreq(dev);
+	unsigned int value;
+	int ret;
+
+	if (!df->governor)
+		return -EINVAL;
+
+	ret = sscanf(buf, "%u", &value);
+	if (ret != 1)
+		return -EINVAL;
+
+	df->governor->event_handler(df, DEVFREQ_GOV_UPDATE_INTERVAL, &value);
+	ret = count;
+
+	return ret;
+}
+static DEVICE_ATTR_RW(polling_interval);
+
 static ssize_t timer_show(struct device *dev,
 			     struct device_attribute *attr, char *buf)
 {
@@ -1787,21 +1830,36 @@ static ssize_t timer_store(struct device *dev, struct device_attribute *attr,
 }
 static DEVICE_ATTR_RW(timer);
 
-static struct attribute *devfreq_attrs[] = {
-	&dev_attr_name.attr,
-	&dev_attr_governor.attr,
-	&dev_attr_available_governors.attr,
-	&dev_attr_cur_freq.attr,
-	&dev_attr_available_frequencies.attr,
-	&dev_attr_target_freq.attr,
-	&dev_attr_polling_interval.attr,
-	&dev_attr_min_freq.attr,
-	&dev_attr_max_freq.attr,
-	&dev_attr_trans_stat.attr,
-	&dev_attr_timer.attr,
-	NULL,
-};
-ATTRIBUTE_GROUPS(devfreq);
+#define CREATE_SYSFS_FILE(df, name)					\
+{									\
+	int ret;							\
+	ret = sysfs_create_file(&df->dev.kobj, &dev_attr_##name.attr);	\
+	if (ret < 0) {							\
+		dev_warn(&df->dev,					\
+			"Unable to create attr(%s)\n", "##name");	\
+	}								\
+}									\
+
+/* Create the specific sysfs files which depend on each governor. */
+static void create_sysfs_files(struct devfreq *devfreq,
+				const struct devfreq_governor *gov)
+{
+	if (IS_SUPPORTED_ATTR(gov->attrs, POLLING_INTERVAL))
+		CREATE_SYSFS_FILE(devfreq, polling_interval);
+	if (IS_SUPPORTED_ATTR(gov->attrs, TIMER))
+		CREATE_SYSFS_FILE(devfreq, timer);
+}
+
+/* Remove the specific sysfs files which depend on each governor. */
+static void remove_sysfs_files(struct devfreq *devfreq,
+				const struct devfreq_governor *gov)
+{
+	if (IS_SUPPORTED_ATTR(gov->attrs, POLLING_INTERVAL))
+		sysfs_remove_file(&devfreq->dev.kobj,
+				&dev_attr_polling_interval.attr);
+	if (IS_SUPPORTED_ATTR(gov->attrs, TIMER))
+		sysfs_remove_file(&devfreq->dev.kobj, &dev_attr_timer.attr);
+}
 
 /**
  * devfreq_summary_show() - Show the summary of the devfreq devices
@@ -1858,8 +1916,12 @@ static int devfreq_summary_show(struct seq_file *s, void *data)
 		mutex_lock(&devfreq->lock);
 		cur_freq = devfreq->previous_freq;
 		get_freq_range(devfreq, &min_freq, &max_freq);
-		polling_ms = devfreq->profile->polling_ms;
 		timer = devfreq->profile->timer;
+
+		if (IS_SUPPORTED_ATTR(devfreq->governor->attrs, POLLING_INTERVAL))
+			polling_ms = devfreq->profile->polling_ms;
+		else
+			polling_ms = 0;
 		mutex_unlock(&devfreq->lock);
 
 		seq_printf(s,
diff --git a/drivers/devfreq/governor.h b/drivers/devfreq/governor.h
index 7dbb110a869e..df413b851bb2 100644
--- a/drivers/devfreq/governor.h
+++ b/drivers/devfreq/governor.h
@@ -35,10 +35,21 @@
 #define DEVFREQ_GOV_FLAG_IMMUTABLE			BIT(0)
 #define DEVFREQ_GOV_FLAG_IRQ_DRIVEN			BIT(1)
 
+/*
+ * Definition of governor attribute flags except for common sysfs attributes
+ * - DEVFREQ_GOV_ATTR_POLLING_INTERVAL
+ *   : Indicate polling_interal sysfs attribute
+ * - DEVFREQ_GOV_ATTR_TIMER
+ *   : Indicate timer sysfs attribute
+ */
+#define DEVFREQ_GOV_ATTR_POLLING_INTERVAL		BIT(0)
+#define DEVFREQ_GOV_ATTR_TIMER				BIT(1)
+
 /**
  * struct devfreq_governor - Devfreq policy governor
  * @node:		list node - contains registered devfreq governors
  * @name:		Governor's name
+ * @attrs:		Governor's sysfs attribute flags
  * @flags:		Governor's feature flags
  * @get_target_freq:	Returns desired operating frequency for the device.
  *			Basically, get_target_freq will run
@@ -57,6 +68,7 @@ struct devfreq_governor {
 	struct list_head node;
 
 	const char name[DEVFREQ_NAME_LEN];
+	const u64 attrs;
 	const u64 flags;
 	int (*get_target_freq)(struct devfreq *this, unsigned long *freq);
 	int (*event_handler)(struct devfreq *devfreq,
diff --git a/drivers/devfreq/governor_simpleondemand.c b/drivers/devfreq/governor_simpleondemand.c
index 1b314e1df028..d57b82a2b570 100644
--- a/drivers/devfreq/governor_simpleondemand.c
+++ b/drivers/devfreq/governor_simpleondemand.c
@@ -117,6 +117,8 @@ static int devfreq_simple_ondemand_handler(struct devfreq *devfreq,
 
 static struct devfreq_governor devfreq_simple_ondemand = {
 	.name = DEVFREQ_GOV_SIMPLE_ONDEMAND,
+	.attrs = DEVFREQ_GOV_ATTR_POLLING_INTERVAL
+		| DEVFREQ_GOV_ATTR_TIMER,
 	.get_target_freq = devfreq_simple_ondemand_func,
 	.event_handler = devfreq_simple_ondemand_handler,
 };
diff --git a/drivers/devfreq/tegra30-devfreq.c b/drivers/devfreq/tegra30-devfreq.c
index faa1aecf2a31..8f5b60bef336 100644
--- a/drivers/devfreq/tegra30-devfreq.c
+++ b/drivers/devfreq/tegra30-devfreq.c
@@ -765,6 +765,7 @@ static int tegra_governor_event_handler(struct devfreq *devfreq,
 
 static struct devfreq_governor tegra_devfreq_governor = {
 	.name = "tegra_actmon",
+	.attrs = DEVFREQ_GOV_ATTR_POLLING_INTERVAL,
 	.flags = DEVFREQ_GOV_FLAG_IMMUTABLE
 		| DEVFREQ_GOV_FLAG_IRQ_DRIVEN,
 	.get_target_freq = tegra_governor_get_target,
-- 
2.17.1