[RFC 1/3] PM: QoS: Introduce cpufreq minimum load QoS

[Benjamin Gaignard]

Introduce cpufreq minimum load QoS, based on the "raw" low-level
PM QoS, to represent the minimum expected cpu load by various devices.

The cpufreq_minload_qos_limit() helper is defined to retrieve the
aggregated constraints.

Signed-off-by: Benjamin Gaignard <benjamin.gaignard@xxxxxx>
---
 include/linux/pm_qos.h |  12 +++
 kernel/power/qos.c     | 213 +++++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 225 insertions(+)

diff --git a/include/linux/pm_qos.h b/include/linux/pm_qos.h
index 4a69d4af3ff8..e2cc099322e3 100644
--- a/include/linux/pm_qos.h
+++ b/include/linux/pm_qos.h
@@ -316,4 +316,16 @@ int freq_qos_remove_notifier(struct freq_constraints *qos,
 			     enum freq_qos_req_type type,
 			     struct notifier_block *notifier);
 
+/* Definitions related to the cpufreq minimum load QoS. */
+
+#define CPUFREQ_GOV_QOS_MIN_LOAD_DEFAULT_VALUE	0
+#define CPUFREQ_GOV_QOS_MIN_LOAD_MAX_VALUE	10
+
+s32 cpufreq_minload_qos_limit(void);
+bool cpufreq_minload_qos_request_active(struct pm_qos_request *req);
+void cpufreq_minload_qos_add_request(struct pm_qos_request *req, s32 value);
+void cpufreq_minload_qos_update_request(struct pm_qos_request *req,
+					s32 new_value);
+void cpufreq_minload_qos_remove_request(struct pm_qos_request *req);
+
 #endif
diff --git a/kernel/power/qos.c b/kernel/power/qos.c
index db0bed2cae26..df2fdd962f35 100644
--- a/kernel/power/qos.c
+++ b/kernel/power/qos.c
@@ -671,3 +671,216 @@ int freq_qos_remove_notifier(struct freq_constraints *qos,
 	return ret;
 }
 EXPORT_SYMBOL_GPL(freq_qos_remove_notifier);
+
+/* Definitions related to the cpufreq minimum load QoS. */
+
+static struct pm_qos_constraints cpufreq_minload_constraints = {
+	.list = PLIST_HEAD_INIT(cpufreq_minload_constraints.list),
+	.target_value = CPUFREQ_GOV_QOS_MIN_LOAD_DEFAULT_VALUE,
+	.default_value = CPUFREQ_GOV_QOS_MIN_LOAD_DEFAULT_VALUE,
+	.no_constraint_value = CPUFREQ_GOV_QOS_MIN_LOAD_DEFAULT_VALUE,
+	.type = PM_QOS_MAX,
+};
+
+/**
+ * cpufreq_minload_qos_limit - Return current system-wide cpufreq
+ * minimum load QoS limit.
+ */
+s32 cpufreq_minload_qos_limit(void)
+{
+	return pm_qos_read_value(&cpufreq_minload_constraints);
+}
+EXPORT_SYMBOL_GPL(cpufreq_minload_qos_limit);
+
+/**
+ * cpufreq_minload_qos_request_active - Check the given PM QoS request.
+ * @req: PM QoS request to check.
+ *
+ * Return: 'true' if @req has been added to the cpufreq minimum load
+ * QoS list, 'false' otherwise.
+ */
+bool cpufreq_minload_qos_request_active(struct pm_qos_request *req)
+{
+	return req->qos == &cpufreq_minload_constraints;
+}
+EXPORT_SYMBOL_GPL(cpufreq_minload_qos_request_active);
+
+/**
+ * cpufreq_minload_qos_add_request - Add new cpufreq minimum load QoS request.
+ * @req: Pointer to a preallocated handle.
+ * @value: Requested constraint value.
+ *
+ * Use @value to initialize the request handle pointed to by @req, insert it as
+ * a new entry to the cpufreq minimum load QoS list and recompute the effective
+ * QoS constraint for that list.
+ *
+ * Callers need to save the handle for later use in updates and removal of the
+ * QoS request represented by it.
+ */
+void cpufreq_minload_qos_add_request(struct pm_qos_request *req, s32 value)
+{
+	if (!req)
+		return;
+
+	if (cpufreq_minload_qos_request_active(req)) {
+		WARN(1, KERN_ERR "%s called for already added request\n", __func__);
+		return;
+	}
+
+	trace_pm_qos_add_request(value);
+
+	req->qos = &cpufreq_minload_constraints;
+	pm_qos_update_target(req->qos, &req->node, PM_QOS_ADD_REQ, value);
+}
+EXPORT_SYMBOL_GPL(cpufreq_minload_qos_add_request);
+
+/**
+ * cpufreq_minload_qos_update_request - Modify existing cpufreq minimum load
+ * QoS request.
+ * @req : QoS request to update.
+ * @new_value: New requested constraint value.
+ *
+ * Use @new_value to update the QoS request represented by @req in the cpufreq
+ * minimum load QoS list along with updating the effective constraint value for
+ * that list.
+ */
+void cpufreq_minload_qos_update_request(struct pm_qos_request *req,
+					s32 new_value)
+{
+	if (!req)
+		return;
+
+	if (!cpufreq_minload_qos_request_active(req)) {
+		WARN(1, KERN_ERR "%s called for unknown object\n", __func__);
+		return;
+	}
+
+	trace_pm_qos_update_request(new_value);
+
+	if (new_value == req->node.prio)
+		return;
+
+	pm_qos_update_target(req->qos, &req->node, PM_QOS_UPDATE_REQ, new_value);
+}
+EXPORT_SYMBOL_GPL(cpufreq_minload_qos_update_request);
+
+/**
+ * cpufreq_minload_qos_remove_request - Remove existing cpufreq minimum load QoS
+ * request.
+ * @req: QoS request to remove.
+ *
+ * Remove the cpufreq minimum load QoS request represented by @req from the
+ * cpufreq minimum load QoS list along with updating the effective constraint
+ * value for that list.
+ */
+void cpufreq_minload_qos_remove_request(struct pm_qos_request *req)
+{
+	if (!req)
+		return;
+
+	if (!cpufreq_minload_qos_request_active(req)) {
+		WARN(1, KERN_ERR "%s called for unknown object\n", __func__);
+		return;
+	}
+
+	trace_pm_qos_remove_request(PM_QOS_DEFAULT_VALUE);
+
+	pm_qos_update_target(req->qos, &req->node,
+			     PM_QOS_REMOVE_REQ, PM_QOS_DEFAULT_VALUE);
+	memset(req, 0, sizeof(*req));
+}
+EXPORT_SYMBOL_GPL(cpufreq_minload_qos_remove_request);
+
+/* User space interface to the cpufreq minimum load QoS via misc device. */
+
+static int cpufreq_minload_qos_open(struct inode *inode, struct file *filp)
+{
+	struct pm_qos_request *req;
+
+	req = kzalloc(sizeof(*req), GFP_KERNEL);
+	if (!req)
+		return -ENOMEM;
+
+	cpufreq_minload_qos_add_request(req, PM_QOS_DEFAULT_VALUE);
+	filp->private_data = req;
+
+	return 0;
+}
+
+static int cpufreq_minload_qos_release(struct inode *inode, struct file *filp)
+{
+	struct pm_qos_request *req = filp->private_data;
+
+	filp->private_data = NULL;
+
+	cpufreq_minload_qos_remove_request(req);
+	kfree(req);
+
+	return 0;
+}
+
+static ssize_t cpufreq_minload_qos_read(struct file *filp, char __user *buf,
+					size_t count, loff_t *f_pos)
+{
+	struct pm_qos_request *req = filp->private_data;
+	unsigned long flags;
+	s32 value;
+
+	if (!req || !cpufreq_minload_qos_request_active(req))
+		return -EINVAL;
+
+	spin_lock_irqsave(&pm_qos_lock, flags);
+	value = pm_qos_get_value(&cpufreq_minload_constraints);
+	spin_unlock_irqrestore(&pm_qos_lock, flags);
+
+	return simple_read_from_buffer(buf, count, f_pos, &value, sizeof(s32));
+}
+
+static ssize_t cpufreq_minload_qos_write(struct file *filp,
+					 const char __user *buf,
+					 size_t count, loff_t *f_pos)
+{
+	s32 value;
+
+	if (count == sizeof(s32)) {
+		if (copy_from_user(&value, buf, sizeof(s32)))
+			return -EFAULT;
+	} else {
+		int ret;
+
+		ret = kstrtos32_from_user(buf, count, 16, &value);
+		if (ret)
+			return ret;
+	}
+
+	cpufreq_minload_qos_update_request(filp->private_data, value);
+
+	return count;
+}
+
+static const struct file_operations cpufreq_minload_qos_fops = {
+	.write = cpufreq_minload_qos_write,
+	.read = cpufreq_minload_qos_read,
+	.open = cpufreq_minload_qos_open,
+	.release = cpufreq_minload_qos_release,
+	.llseek = noop_llseek,
+};
+
+static struct miscdevice cpufreq_minload_qos_miscdev = {
+	.minor = MISC_DYNAMIC_MINOR,
+	.name = "cpufreq_minimum_load",
+	.fops = &cpufreq_minload_qos_fops,
+};
+
+static int __init cpufreq_minload_qos_init(void)
+{
+	int ret;
+
+	ret = misc_register(&cpufreq_minload_qos_miscdev);
+	if (ret < 0)
+		pr_err("%s: %s setup failed\n", __func__,
+		       cpufreq_minload_qos_miscdev.name);
+
+	return ret;
+}
+late_initcall(cpufreq_minload_qos_init);
-- 
2.15.0