[PATCH 3/4] thermal: convert cpu_cooling to use an IDA

[Matthew Wilcox <mawilcox@linuxonhyperv.com>]

From: Matthew Wilcox <mawilcox@microsoft.com>

thermal cpu 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.

The cooling_cpufreq_lock was being used to protect cpufreq_dev_count as
well as the IDR.  Rather than keep the mutex to protect a single integer,
I expanded the scope of cooling_list_lock to also cover cpufreq_dev_count.
We could also convert cpufreq_dev_count into an atomic.

Signed-off-by: Matthew Wilcox <mawilcox@microsoft.com>
---
 drivers/thermal/cpu_cooling.c | 63 ++++++++-----------------------------------
 1 file changed, 11 insertions(+), 52 deletions(-)

diff --git a/drivers/thermal/cpu_cooling.c b/drivers/thermal/cpu_cooling.c
index 9ce0e9eef923..ea3cf7b5cb5b 100644
--- a/drivers/thermal/cpu_cooling.c
+++ b/drivers/thermal/cpu_cooling.c
@@ -26,6 +26,7 @@
 #include <linux/thermal.h>
 #include <linux/cpufreq.h>
 #include <linux/err.h>
+#include <linux/idr.h>
 #include <linux/pm_opp.h>
 #include <linux/slab.h>
 #include <linux/cpu.h>
@@ -104,50 +105,13 @@ struct cpufreq_cooling_device {
 	struct device *cpu_dev;
 	get_static_t plat_get_static_power;
 };
-static DEFINE_IDR(cpufreq_idr);
-static DEFINE_MUTEX(cooling_cpufreq_lock);
+static DEFINE_IDA(cpufreq_ida);
 
 static unsigned int cpufreq_dev_count;
 
 static DEFINE_MUTEX(cooling_list_lock);
 static LIST_HEAD(cpufreq_dev_list);
 
-/**
- * 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(&cooling_cpufreq_lock);
-	ret = idr_alloc(idr, NULL, 0, 0, GFP_KERNEL);
-	mutex_unlock(&cooling_cpufreq_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(&cooling_cpufreq_lock);
-	idr_remove(idr, id);
-	mutex_unlock(&cooling_cpufreq_lock);
-}
-
 /* Below code defines functions to be used for cpufreq as cooling device */
 
 /**
@@ -874,11 +838,12 @@ __cpufreq_cooling_register(struct device_node *np,
 		cooling_ops = &cpufreq_cooling_ops;
 	}
 
-	ret = get_idr(&cpufreq_idr, &cpufreq_dev->id);
-	if (ret) {
+	ret = ida_simple_get(&cpufreq_ida, 0, 0, GFP_KERNEL);
+	if (ret < 0) {
 		cool_dev = ERR_PTR(ret);
 		goto free_power_table;
 	}
+	cpufreq_dev->id = ret;
 
 	/* Fill freq-table in descending order of frequencies */
 	for (i = 0, freq = -1; i <= cpufreq_dev->max_level; i++) {
@@ -898,27 +863,24 @@ __cpufreq_cooling_register(struct device_node *np,
 	cool_dev = thermal_of_cooling_device_register(np, dev_name, cpufreq_dev,
 						      cooling_ops);
 	if (IS_ERR(cool_dev))
-		goto remove_idr;
+		goto remove_ida;
 
 	cpufreq_dev->clipped_freq = cpufreq_dev->freq_table[0];
 	cpufreq_dev->cool_dev = cool_dev;
 
-	mutex_lock(&cooling_cpufreq_lock);
-
 	mutex_lock(&cooling_list_lock);
 	list_add(&cpufreq_dev->node, &cpufreq_dev_list);
-	mutex_unlock(&cooling_list_lock);
 
 	/* Register the notifier for first cpufreq cooling device */
 	if (!cpufreq_dev_count++)
 		cpufreq_register_notifier(&thermal_cpufreq_notifier_block,
 					  CPUFREQ_POLICY_NOTIFIER);
-	mutex_unlock(&cooling_cpufreq_lock);
+	mutex_unlock(&cooling_list_lock);
 
 	goto put_policy;
 
-remove_idr:
-	release_idr(&cpufreq_idr, cpufreq_dev->id);
+remove_ida:
+	ida_simple_remove(&cpufreq_ida, cpufreq_dev->id);
 free_power_table:
 	kfree(cpufreq_dev->dyn_power_table);
 free_table:
@@ -1059,20 +1021,17 @@ void cpufreq_cooling_unregister(struct thermal_cooling_device *cdev)
 
 	cpufreq_dev = cdev->devdata;
 
+	mutex_lock(&cooling_list_lock);
 	/* Unregister the notifier for the last cpufreq cooling device */
-	mutex_lock(&cooling_cpufreq_lock);
 	if (!--cpufreq_dev_count)
 		cpufreq_unregister_notifier(&thermal_cpufreq_notifier_block,
 					    CPUFREQ_POLICY_NOTIFIER);
 
-	mutex_lock(&cooling_list_lock);
 	list_del(&cpufreq_dev->node);
 	mutex_unlock(&cooling_list_lock);
 
-	mutex_unlock(&cooling_cpufreq_lock);
-
 	thermal_cooling_device_unregister(cpufreq_dev->cool_dev);
-	release_idr(&cpufreq_idr, cpufreq_dev->id);
+	ida_simple_remove(&cpufreq_ida, cpufreq_dev->id);
 	kfree(cpufreq_dev->dyn_power_table);
 	kfree(cpufreq_dev->time_in_idle_timestamp);
 	kfree(cpufreq_dev->time_in_idle);
-- 
2.11.0