powercap/drivers/dtpm: Use container_of instead of a private data field

The dtpm framework provides an API to allocate a dtpm node. However
when a backend dtpm driver needs to allocate a dtpm node it must
define its own structure and store the pointer of this structure in
the private field of the dtpm structure.

It is more elegant to use the container_of macro and add the dtpm
structure inside the dtpm backend specific structure. The code will be
able to deal properly with the dtpm structure as a generic entity,
making all this even more self-encapsulated.

The dtpm_alloc() function does no longer make sense as the dtpm
structure will be allocated when allocating the device specific dtpm
structure. The dtpm_init() is provided instead.

Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Reviewed-by: Lukasz Luba <lukasz.luba@arm.com>
Link: https://lore.kernel.org/r/20210312130411.29833-4-daniel.lezcano@linaro.org

drivers/powercap/dtpm.c

@@ -357,24 +357,18 @@ static struct powercap_zone_ops zone_ops = {
 };
 
 /**
- * dtpm_alloc - Allocate and initialize a dtpm struct
- * @name: a string specifying the name of the node
- *
- * Return: a struct dtpm pointer, NULL in case of error
+ * dtpm_init - Allocate and initialize a dtpm struct
+ * @dtpm: The dtpm struct pointer to be initialized
+ * @ops: The dtpm device specific ops, NULL for a virtual node
  */
-struct dtpm *dtpm_alloc(struct dtpm_ops *ops)
+void dtpm_init(struct dtpm *dtpm, struct dtpm_ops *ops)
 {
-	struct dtpm *dtpm;
-
-	dtpm = kzalloc(sizeof(*dtpm), GFP_KERNEL);
 	if (dtpm) {
 		INIT_LIST_HEAD(&dtpm->children);
 		INIT_LIST_HEAD(&dtpm->sibling);
 		dtpm->weight = 1024;
 		dtpm->ops = ops;
 	}
-
-	return dtpm;
 }
 
 /**
@@ -465,7 +459,7 @@ int dtpm_register(const char *name, struct dtpm *dtpm, struct dtpm *parent)
 	return 0;
 }
 
-static int __init dtpm_init(void)
+static int __init init_dtpm(void)
 {
 	struct dtpm_descr *dtpm_descr;
 
@@ -480,4 +474,4 @@ static int __init dtpm_init(void)
 
 	return 0;
 }
-late_initcall(dtpm_init);
+late_initcall(init_dtpm);

drivers/powercap/dtpm_cpu.c

@@ -25,16 +25,22 @@
 #include <linux/slab.h>
 #include <linux/units.h>
 
-static DEFINE_PER_CPU(struct dtpm *, dtpm_per_cpu);
-
 struct dtpm_cpu {
+	struct dtpm dtpm;
 	struct freq_qos_request qos_req;
 	int cpu;
 };
 
+static DEFINE_PER_CPU(struct dtpm_cpu *, dtpm_per_cpu);
+
+static struct dtpm_cpu *to_dtpm_cpu(struct dtpm *dtpm)
+{
+	return container_of(dtpm, struct dtpm_cpu, dtpm);
+}
+
 static u64 set_pd_power_limit(struct dtpm *dtpm, u64 power_limit)
 {
-	struct dtpm_cpu *dtpm_cpu = dtpm->private;
+	struct dtpm_cpu *dtpm_cpu = to_dtpm_cpu(dtpm);
 	struct em_perf_domain *pd = em_cpu_get(dtpm_cpu->cpu);
 	struct cpumask cpus;
 	unsigned long freq;
@@ -64,7 +70,7 @@ static u64 set_pd_power_limit(struct dtpm *dtpm, u64 power_limit)
 
 static u64 get_pd_power_uw(struct dtpm *dtpm)
 {
-	struct dtpm_cpu *dtpm_cpu = dtpm->private;
+	struct dtpm_cpu *dtpm_cpu = to_dtpm_cpu(dtpm);
 	struct em_perf_domain *pd;
 	struct cpumask cpus;
 	unsigned long freq;
@@ -90,7 +96,7 @@ static u64 get_pd_power_uw(struct dtpm *dtpm)
 
 static int update_pd_power_uw(struct dtpm *dtpm)
 {
-	struct dtpm_cpu *dtpm_cpu = dtpm->private;
+	struct dtpm_cpu *dtpm_cpu = to_dtpm_cpu(dtpm);
 	struct em_perf_domain *em = em_cpu_get(dtpm_cpu->cpu);
 	struct cpumask cpus;
 	int nr_cpus;
@@ -111,7 +117,7 @@ static int update_pd_power_uw(struct dtpm *dtpm)
 
 static void pd_release(struct dtpm *dtpm)
 {
-	struct dtpm_cpu *dtpm_cpu = dtpm->private;
+	struct dtpm_cpu *dtpm_cpu = to_dtpm_cpu(dtpm);
 
 	if (freq_qos_request_active(&dtpm_cpu->qos_req))
 		freq_qos_remove_request(&dtpm_cpu->qos_req);
@@ -129,20 +135,19 @@ static struct dtpm_ops dtpm_ops = {
 static int cpuhp_dtpm_cpu_offline(unsigned int cpu)
 {
 	struct em_perf_domain *pd;
-	struct dtpm *dtpm;
+	struct dtpm_cpu *dtpm_cpu;
 
 	pd = em_cpu_get(cpu);
 	if (!pd)
 		return -EINVAL;
 
-	dtpm = per_cpu(dtpm_per_cpu, cpu);
+	dtpm_cpu = per_cpu(dtpm_per_cpu, cpu);
 
-	return dtpm_update_power(dtpm);
+	return dtpm_update_power(&dtpm_cpu->dtpm);
 }
 
 static int cpuhp_dtpm_cpu_online(unsigned int cpu)
 {
-	struct dtpm *dtpm;
 	struct dtpm_cpu *dtpm_cpu;
 	struct cpufreq_policy *policy;
 	struct em_perf_domain *pd;
@@ -157,27 +162,23 @@ static int cpuhp_dtpm_cpu_online(unsigned int cpu)
 	if (!pd)
 		return -EINVAL;
 
-	dtpm = per_cpu(dtpm_per_cpu, cpu);
-	if (dtpm)
-		return dtpm_update_power(dtpm);
-
-	dtpm = dtpm_alloc(&dtpm_ops);
-	if (!dtpm)
-		return -EINVAL;
+	dtpm_cpu = per_cpu(dtpm_per_cpu, cpu);
+	if (dtpm_cpu)
+		return dtpm_update_power(&dtpm_cpu->dtpm);
 
 	dtpm_cpu = kzalloc(sizeof(*dtpm_cpu), GFP_KERNEL);
 	if (!dtpm_cpu)
-		goto out_kfree_dtpm;
+		return -ENOMEM;
 
-	dtpm->private = dtpm_cpu;
+	dtpm_init(&dtpm_cpu->dtpm, &dtpm_ops);
 	dtpm_cpu->cpu = cpu;
 
 	for_each_cpu(cpu, policy->related_cpus)
-		per_cpu(dtpm_per_cpu, cpu) = dtpm;
+		per_cpu(dtpm_per_cpu, cpu) = dtpm_cpu;
 
 	snprintf(name, sizeof(name), "cpu%d-cpufreq", dtpm_cpu->cpu);
 
-	ret = dtpm_register(name, dtpm, NULL);
+	ret = dtpm_register(name, &dtpm_cpu->dtpm, NULL);
 	if (ret)
 		goto out_kfree_dtpm_cpu;
 
@@ -190,17 +191,14 @@ static int cpuhp_dtpm_cpu_online(unsigned int cpu)
 	return 0;
 
 out_dtpm_unregister:
-	dtpm_unregister(dtpm);
+	dtpm_unregister(&dtpm_cpu->dtpm);
 	dtpm_cpu = NULL;
-	dtpm = NULL;
 
 out_kfree_dtpm_cpu:
 	for_each_cpu(cpu, policy->related_cpus)
 		per_cpu(dtpm_per_cpu, cpu) = NULL;
 	kfree(dtpm_cpu);
 
-out_kfree_dtpm:
-	kfree(dtpm);
 	return ret;
 }
 

include/linux/dtpm.h

@@ -23,7 +23,6 @@ struct dtpm {
 	u64 power_max;
 	u64 power_min;
 	int weight;
-	void *private;
 };
 
 struct dtpm_ops {
@@ -65,7 +64,7 @@ int dtpm_update_power(struct dtpm *dtpm);
 
 int dtpm_release_zone(struct powercap_zone *pcz);
 
-struct dtpm *dtpm_alloc(struct dtpm_ops *ops);
+void dtpm_init(struct dtpm *dtpm, struct dtpm_ops *ops);
 
 void dtpm_unregister(struct dtpm *dtpm);