thermal: convert devfreq_cooling to use an IDA

thermal devfreq cooling does not use the ability to look up pointers by
ID, so convert it from using an IDR to the more space-efficient IDA.
Signed-off-by: Matthew Wilcox <mawilcox@microsoft.com>
Signed-off-by: Zhang Rui <rui.zhang@intel.com>

drivers/thermal/devfreq_cooling.c

@@ -21,14 +21,14 @@
 #include <linux/devfreq.h>
 #include <linux/devfreq_cooling.h>
 #include <linux/export.h>
+#include <linux/idr.h>
 #include <linux/slab.h>
 #include <linux/pm_opp.h>
 #include <linux/thermal.h>
 
 #include <trace/events/thermal.h>
 
-static DEFINE_MUTEX(devfreq_lock);
-static DEFINE_IDR(devfreq_idr);
+static DEFINE_IDA(devfreq_ida);
 
 /**
  * struct devfreq_cooling_device - Devfreq cooling device
@@ -57,42 +57,6 @@ struct devfreq_cooling_device {
 	struct devfreq_cooling_power *power_ops;
 };
 
-/**
- * get_idr - function to get a unique id.
- * @idr: struct idr * handle used to create a id.
- * @id: int * value generated by this function.
- *
- * This function will populate @id with an unique
- * id, using the idr API.
- *
- * Return: 0 on success, an error code on failure.
- */
-static int get_idr(struct idr *idr, int *id)
-{
-	int ret;
-
-	mutex_lock(&devfreq_lock);
-	ret = idr_alloc(idr, NULL, 0, 0, GFP_KERNEL);
-	mutex_unlock(&devfreq_lock);
-	if (unlikely(ret < 0))
-		return ret;
-	*id = ret;
-
-	return 0;
-}
-
-/**
- * release_idr - function to free the unique id.
- * @idr: struct idr * handle used for creating the id.
- * @id: int value representing the unique id.
- */
-static void release_idr(struct idr *idr, int id)
-{
-	mutex_lock(&devfreq_lock);
-	idr_remove(idr, id);
-	mutex_unlock(&devfreq_lock);
-}
-
 /**
  * partition_enable_opps() - disable all opps above a given state
  * @dfc:	Pointer to devfreq we are operating on
@@ -496,9 +460,10 @@ of_devfreq_cooling_register_power(struct device_node *np, struct devfreq *df,
 	if (err)
 		goto free_dfc;
 
-	err = get_idr(&devfreq_idr, &dfc->id);
-	if (err)
+	err = ida_simple_get(&devfreq_ida, 0, 0, GFP_KERNEL);
+	if (err < 0)
 		goto free_tables;
+	dfc->id = err;
 
 	snprintf(dev_name, sizeof(dev_name), "thermal-devfreq-%d", dfc->id);
 
@@ -509,15 +474,15 @@ of_devfreq_cooling_register_power(struct device_node *np, struct devfreq *df,
 		dev_err(df->dev.parent,
 			"Failed to register devfreq cooling device (%d)\n",
 			err);
-		goto release_idr;
+		goto release_ida;
 	}
 
 	dfc->cdev = cdev;
 
 	return cdev;
 
-release_idr:
-	release_idr(&devfreq_idr, dfc->id);
+release_ida:
+	ida_simple_remove(&devfreq_ida, dfc->id);
 free_tables:
 	kfree(dfc->power_table);
 	kfree(dfc->freq_table);
@@ -565,7 +530,7 @@ void devfreq_cooling_unregister(struct thermal_cooling_device *cdev)
 	dfc = cdev->devdata;
 
 	thermal_cooling_device_unregister(dfc->cdev);
-	release_idr(&devfreq_idr, dfc->id);
+	ida_simple_remove(&devfreq_ida, dfc->id);
 	kfree(dfc->power_table);
 	kfree(dfc->freq_table);