PM / QoS: Make it possible to expose device latency tolerance to userspace

Typically when a device is created the bus core it belongs to (for example
PCI) does not know if the device supports things like latency tolerance.
This is left to the driver that binds to the device in question. However,
at that time the device has already been created and there is no way to set
its dev->power.set_latency_tolerance anymore.

So follow what has been done for other PM QoS attributes as well and allow
drivers to expose and hide latency tolerance from userspace, if the device
supports it.

Acked-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Signed-off-by: Mika Westerberg <mika.westerberg@linux.intel.com>
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Lee Jones <lee.jones@linaro.org>

1 files changed, 37 insertions, 0 deletions

diff --git a/drivers/base/power/qos.c b/drivers/base/power/qos.c
index e56d538d039e..7f3646e459cb 100644
--- a/drivers/base/power/qos.c
+++ b/drivers/base/power/qos.c
@@ -883,3 +883,40 @@ int dev_pm_qos_update_user_latency_tolerance(struct device *dev, s32 val)
         mutex_unlock(&dev_pm_qos_mtx);
         return ret;
 }
+
+/**
+ * dev_pm_qos_expose_latency_tolerance - Expose latency tolerance to userspace
+ * @dev: Device whose latency tolerance to expose
+ */
+int dev_pm_qos_expose_latency_tolerance(struct device *dev)
+{
+        int ret;
+
+        if (!dev->power.set_latency_tolerance)
+                return -EINVAL;
+
+        mutex_lock(&dev_pm_qos_sysfs_mtx);
+        ret = pm_qos_sysfs_add_latency_tolerance(dev);
+        mutex_unlock(&dev_pm_qos_sysfs_mtx);
+
+        return ret;
+}
+EXPORT_SYMBOL_GPL(dev_pm_qos_expose_latency_tolerance);
+
+/**
+ * dev_pm_qos_hide_latency_tolerance - Hide latency tolerance from userspace
+ * @dev: Device whose latency tolerance to hide
+ */
+void dev_pm_qos_hide_latency_tolerance(struct device *dev)
+{
+        mutex_lock(&dev_pm_qos_sysfs_mtx);
+        pm_qos_sysfs_remove_latency_tolerance(dev);
+        mutex_unlock(&dev_pm_qos_sysfs_mtx);
+
+        /* Remove the request from user space now */
+        pm_runtime_get_sync(dev);
+        dev_pm_qos_update_user_latency_tolerance(dev,
+                PM_QOS_LATENCY_TOLERANCE_NO_CONSTRAINT);
+        pm_runtime_put(dev);
+}
+EXPORT_SYMBOL_GPL(dev_pm_qos_hide_latency_tolerance);