[PATCH v2 1/5] driver/perf: Add identifier sysfs file for CMN

[Jing Zhang <renyu.zj@linux.alibaba.com>]

To allow userspace to identify the specific implementation of the device,
add an "identifier" sysfs file.

The perf tool can match the arm CMN metric through the identifier.

Signed-off-by: Jing Zhang <renyu.zj@linux.alibaba.com>
---
 drivers/perf/arm-cmn.c | 49 +++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 49 insertions(+)

diff --git a/drivers/perf/arm-cmn.c b/drivers/perf/arm-cmn.c
index c968986..f425610 100644
--- a/drivers/perf/arm-cmn.c
+++ b/drivers/perf/arm-cmn.c
@@ -334,6 +334,7 @@ struct arm_cmn {
 
 	struct pmu pmu;
 	struct dentry *debug;
+	const char *identifier;
 };
 
 #define to_cmn(p)	container_of(p, struct arm_cmn, pmu)
@@ -1168,10 +1169,41 @@ static ssize_t arm_cmn_cpumask_show(struct device *dev,
 	.attrs = arm_cmn_cpumask_attrs,
 };
 
+static ssize_t arm_cmn_identifier_show(struct device *dev,
+		struct device_attribute *attr, char *buf)
+{
+	struct arm_cmn *cmn = to_cmn(dev_get_drvdata(dev));
+
+	return sysfs_emit(buf, "%s\n", cmn->identifier);
+}
+
+static umode_t arm_cmn_identifier_attr_visible(struct kobject *kobj,
+		struct attribute *attr, int n)
+{
+	struct device *dev = kobj_to_dev(kobj);
+	struct arm_cmn *cmn = to_cmn(dev_get_drvdata(dev));
+
+	if (cmn->identifier == NULL)
+		return 0;
+	return attr->mode;
+};
+
+static struct device_attribute arm_cmn_identifier_attr =
+__ATTR(identifier, 0444, arm_cmn_identifier_show, NULL);
+
+static struct attribute *arm_cmn_identifier_attrs[] = {
+	&arm_cmn_identifier_attr.attr,
+	NULL
+};
+
+static struct attribute_group arm_cmn_identifier_attr_group = {
+	.attrs = arm_cmn_identifier_attrs,
+	.is_visible = arm_cmn_identifier_attr_visible
+};
+
 static const struct attribute_group *arm_cmn_attr_groups[] = {
 	&arm_cmn_event_attrs_group,
 	&arm_cmn_format_attrs_group,
 	&arm_cmn_cpumask_attr_group,
+	&arm_cmn_identifier_attr_group,
 	NULL
 };
 
@@ -2241,6 +2273,22 @@ static int arm_cmn600_of_probe(struct device_node *np)
 	return of_property_read_u32(np, "arm,root-node", &rootnode) ?: rootnode;
 }
 
+const char *arm_cmn_identifier(unsigned long model)
+{
+	switch (model) {
+	case CMN600:
+		return "cmn600";
+	case CMN650:
+		return "cmn650";
+	case CMN700:
+		return "cmn700";
+	case CI700:
+		return "ci700";
+	default:
+		return NULL;
+	}
+}
+
 static int arm_cmn_probe(struct platform_device *pdev)
 {
 	struct arm_cmn *cmn;
@@ -2254,6 +2302,7 @@ static int arm_cmn_probe(struct platform_device *pdev)
 
 	cmn->dev = &pdev->dev;
 	cmn->model = (unsigned long)device_get_match_data(cmn->dev);
+	cmn->identifier = arm_cmn_identifier(cmn->model);
 	platform_set_drvdata(pdev, cmn);
 
 	if (cmn->model == CMN600 && has_acpi_companion(cmn->dev)) {
-- 
1.8.3.1