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Subject[RFC PATCH v5 05/10] thermal: let governors have private data for each thermal zone
Date
A governor may need to store its current state between calls to
throttle(). That state depends on the thermal zone, so store it as
private data in struct thermal_zone_device.

The governors may have two new ops: bind_to_tz() and unbind_from_tz().
When provided, these functions let governors do some initialization
and teardown when they are bound/unbound to a tz and possibly store that
information in the governor_data field of the struct
thermal_zone_device.

Cc: Zhang Rui <rui.zhang@intel.com>
Cc: Eduardo Valentin <edubezval@gmail.com>
Signed-off-by: Javi Merino <javi.merino@arm.com>
---
drivers/thermal/thermal_core.c | 83 ++++++++++++++++++++++++++++++++++++++----
include/linux/thermal.h | 9 +++++
2 files changed, 84 insertions(+), 8 deletions(-)

diff --git a/drivers/thermal/thermal_core.c b/drivers/thermal/thermal_core.c
index 71b0ec0c370d..3da99dd80ad5 100644
--- a/drivers/thermal/thermal_core.c
+++ b/drivers/thermal/thermal_core.c
@@ -72,6 +72,58 @@ static struct thermal_governor *__find_governor(const char *name)
return NULL;
}

+/**
+ * bind_previous_governor() - bind the previous governor of the thermal zone
+ * @tz: a valid pointer to a struct thermal_zone_device
+ * @failed_gov_name: the name of the governor that failed to register
+ *
+ * Register the previous governor of the thermal zone after a new
+ * governor has failed to be bound.
+ */
+static void bind_previous_governor(struct thermal_zone_device *tz,
+ const char *failed_gov_name)
+{
+ if (tz->governor && tz->governor->bind_to_tz) {
+ if (tz->governor->bind_to_tz(tz)) {
+ dev_warn(&tz->device,
+ "governor %s failed to bind and the previous one (%s) failed to register again, thermal zone %s has no governor\n",
+ failed_gov_name, tz->governor->name, tz->type);
+ tz->governor = NULL;
+ }
+ }
+}
+
+/**
+ * thermal_set_governor() - Switch to another governor
+ * @tz: a valid pointer to a struct thermal_zone_device
+ * @new_gov: pointer to the new governor
+ *
+ * Change the governor of thermal zone @tz.
+ *
+ * Return: 0 on success, an error if the new governor's bind_to_tz() failed.
+ */
+static int thermal_set_governor(struct thermal_zone_device *tz,
+ struct thermal_governor *new_gov)
+{
+ int ret = 0;
+
+ if (tz->governor && tz->governor->unbind_from_tz)
+ tz->governor->unbind_from_tz(tz);
+
+ if (new_gov && new_gov->bind_to_tz) {
+ ret = new_gov->bind_to_tz(tz);
+ if (ret) {
+ bind_previous_governor(tz, new_gov->name);
+
+ return ret;
+ }
+ }
+
+ tz->governor = new_gov;
+
+ return ret;
+}
+
int thermal_register_governor(struct thermal_governor *governor)
{
int err;
@@ -104,8 +156,15 @@ int thermal_register_governor(struct thermal_governor *governor)

name = pos->tzp->governor_name;

- if (!strnicmp(name, governor->name, THERMAL_NAME_LENGTH))
- pos->governor = governor;
+ if (!strnicmp(name, governor->name, THERMAL_NAME_LENGTH)) {
+ int ret;
+
+ ret = thermal_set_governor(pos, governor);
+ if (ret)
+ dev_warn(&pos->device,
+ "Failed to set governor %s for thermal zone %s: %d\n",
+ governor->name, pos->type, ret);
+ }
}

mutex_unlock(&thermal_list_lock);
@@ -131,7 +190,7 @@ void thermal_unregister_governor(struct thermal_governor *governor)
list_for_each_entry(pos, &thermal_tz_list, node) {
if (!strnicmp(pos->governor->name, governor->name,
THERMAL_NAME_LENGTH))
- pos->governor = NULL;
+ thermal_set_governor(pos, NULL);
}

mutex_unlock(&thermal_list_lock);
@@ -756,8 +815,9 @@ policy_store(struct device *dev, struct device_attribute *attr,
if (!gov)
goto exit;

- tz->governor = gov;
- ret = count;
+ ret = thermal_set_governor(tz, gov);
+ if (!ret)
+ ret = count;

exit:
mutex_unlock(&thermal_governor_lock);
@@ -1452,6 +1512,7 @@ struct thermal_zone_device *thermal_zone_device_register(const char *type,
int result;
int count;
int passive = 0;
+ struct thermal_governor *governor;

if (type && strlen(type) >= THERMAL_NAME_LENGTH)
return ERR_PTR(-EINVAL);
@@ -1542,9 +1603,15 @@ struct thermal_zone_device *thermal_zone_device_register(const char *type,
mutex_lock(&thermal_governor_lock);

if (tz->tzp)
- tz->governor = __find_governor(tz->tzp->governor_name);
+ governor = __find_governor(tz->tzp->governor_name);
else
- tz->governor = def_governor;
+ governor = def_governor;
+
+ result = thermal_set_governor(tz, governor);
+ if (result) {
+ mutex_unlock(&thermal_governor_lock);
+ goto unregister;
+ }

mutex_unlock(&thermal_governor_lock);

@@ -1634,7 +1701,7 @@ void thermal_zone_device_unregister(struct thermal_zone_device *tz)
device_remove_file(&tz->device, &dev_attr_mode);
device_remove_file(&tz->device, &dev_attr_policy);
remove_trip_attrs(tz);
- tz->governor = NULL;
+ thermal_set_governor(tz, NULL);

thermal_remove_hwmon_sysfs(tz);
release_idr(&thermal_tz_idr, &thermal_idr_lock, tz->id);
diff --git a/include/linux/thermal.h b/include/linux/thermal.h
index 0305cde21a74..1124b7a9358a 100644
--- a/include/linux/thermal.h
+++ b/include/linux/thermal.h
@@ -187,6 +187,7 @@ struct thermal_attr {
* @ops: operations this &thermal_zone_device supports
* @tzp: thermal zone parameters
* @governor: pointer to the governor for this thermal zone
+ * @governor_data: private pointer for governor data
* @thermal_instances: list of &struct thermal_instance of this thermal zone
* @idr: &struct idr to generate unique id for this zone's cooling
* devices
@@ -213,6 +214,7 @@ struct thermal_zone_device {
struct thermal_zone_device_ops *ops;
const struct thermal_zone_params *tzp;
struct thermal_governor *governor;
+ void *governor_data;
struct list_head thermal_instances;
struct idr idr;
struct mutex lock;
@@ -223,12 +225,19 @@ struct thermal_zone_device {
/**
* struct thermal_governor - structure that holds thermal governor information
* @name: name of the governor
+ * @bind_to_tz: callback called when binding to a thermal zone. If it
+ * returns 0, the governor is bound to the thermal zone,
+ * otherwise it fails.
+ * @unbind_from_tz: callback called when a governor is unbound from a
+ * thermal zone.
* @throttle: callback called for every trip point even if temperature is
* below the trip point temperature
* @governor_list: node in thermal_governor_list (in thermal_core.c)
*/
struct thermal_governor {
char name[THERMAL_NAME_LENGTH];
+ int (*bind_to_tz)(struct thermal_zone_device *tz);
+ void (*unbind_from_tz)(struct thermal_zone_device *tz);
int (*throttle)(struct thermal_zone_device *tz, int trip);
struct list_head governor_list;
};
--
1.9.1



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