sched: add per CPU sched_load_boost knob

Commit '858d5751bcf7b6a ("sched: introduce per CPU sched_load_boost
knob")' introduce a new knob sched_load_boost that allows userspace to
provide additional CPU capacity margin to work running on CPUs in
msm-4.9. Userspace could increase this for exceedingly sporadic workloads
in case the existing margin isn't sufficient.

While porting it, sched_load_boost support is ported but missed adding
procfs interface. Add it now to let user space configure the knob.

Change-Id: I4277c63089f6bb5227d257ab7484d50c42827c86
Signed-off-by: Lingutla Chandrasekhar <clingutla@codeaurora.org>

drivers/base/cpu.c

@@ -209,6 +209,59 @@ static struct attribute_group cpu_isolated_attr_group = {
 
 #endif
 
+static ssize_t show_sched_load_boost(struct device *dev,
+				struct device_attribute *attr, char *buf)
+{
+	ssize_t rc;
+	unsigned int boost;
+	struct cpu *cpu = container_of(dev, struct cpu, dev);
+	int cpuid = cpu->dev.id;
+
+	boost = per_cpu(sched_load_boost, cpuid);
+	rc = snprintf(buf, PAGE_SIZE-2, "%d\n", boost);
+
+	return rc;
+}
+
+static ssize_t __ref store_sched_load_boost(struct device *dev,
+				struct device_attribute *attr,
+				const char *buf, size_t count)
+{
+	int err;
+	int boost;
+	struct cpu *cpu = container_of(dev, struct cpu, dev);
+	int cpuid = cpu->dev.id;
+
+	err = kstrtoint(strstrip((char *)buf), 0, &boost);
+	if (err)
+		return err;
+
+	/*
+	 * -100 is low enough to cancel out CPU's load and make it near zro.
+	 * 1000 is close to the maximum value that cpu_util_freq_{walt,pelt}
+	 * can take without overflow.
+	 */
+	if (boost < -100 || boost > 1000)
+		return -EINVAL;
+
+	per_cpu(sched_load_boost, cpuid) = boost;
+
+	return count;
+}
+
+static DEVICE_ATTR(sched_load_boost, 0644,
+		   show_sched_load_boost,
+		   store_sched_load_boost);
+
+static struct attribute *sched_cpu_attrs[] = {
+	&dev_attr_sched_load_boost.attr,
+	NULL
+};
+
+static struct attribute_group sched_cpu_attr_group = {
+	.attrs = sched_cpu_attrs,
+};
+
 static const struct attribute_group *common_cpu_attr_groups[] = {
 #ifdef CONFIG_KEXEC
 	&crash_note_cpu_attr_group,
@@ -216,6 +269,7 @@ static const struct attribute_group *common_cpu_attr_groups[] = {
 #ifdef CONFIG_HOTPLUG_CPU
 	&cpu_isolated_attr_group,
 #endif
+	&sched_cpu_attr_group,
 	NULL
 };
 
@@ -226,6 +280,7 @@ static const struct attribute_group *hotplugable_cpu_attr_groups[] = {
 #ifdef CONFIG_HOTPLUG_CPU
 	&cpu_isolated_attr_group,
 #endif
+	&sched_cpu_attr_group,
 	NULL
 };