driver/perf: Add identifier sysfs file for Yitian 710 DDR

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

The perf tool can match the Yitian 710 DDR metric through the identifier.
Signed-off-by: Jing Zhang <renyu.zj@linux.alibaba.com>
Acked-by: Ian Rogers <irogers@google.com>
Reviewed-by: Shuai Xue <xueshuai@linux.alibaba.com>
Link: https://lore.kernel.org/r/1687245156-61215-2-git-send-email-renyu.zj@linux.alibaba.comSigned-off-by: Will Deacon <will@kernel.org>

drivers/perf/alibaba_uncore_drw_pmu.c

@@ -236,10 +236,37 @@ static const struct attribute_group ali_drw_pmu_cpumask_attr_group = {
 	.attrs = ali_drw_pmu_cpumask_attrs,
 };
 
+static ssize_t ali_drw_pmu_identifier_show(struct device *dev,
+					struct device_attribute *attr,
+					char *page)
+{
+	return sysfs_emit(page, "%s\n", "ali_drw_pmu");
+}
+
+static umode_t ali_drw_pmu_identifier_attr_visible(struct kobject *kobj,
+						struct attribute *attr, int n)
+{
+	return attr->mode;
+}
+
+static struct device_attribute ali_drw_pmu_identifier_attr =
+	__ATTR(identifier, 0444, ali_drw_pmu_identifier_show, NULL);
+
+static struct attribute *ali_drw_pmu_identifier_attrs[] = {
+	&ali_drw_pmu_identifier_attr.attr,
+	NULL
+};
+
+static const struct attribute_group ali_drw_pmu_identifier_attr_group = {
+	.attrs = ali_drw_pmu_identifier_attrs,
+	.is_visible = ali_drw_pmu_identifier_attr_visible
+};
+
 static const struct attribute_group *ali_drw_pmu_attr_groups[] = {
 	&ali_drw_pmu_events_attr_group,
 	&ali_drw_pmu_cpumask_attr_group,
 	&ali_drw_pmu_format_group,
+	&ali_drw_pmu_identifier_attr_group,
 	NULL,
 };