[PATCH V2 2/3] perf/imx_ddr: Add system PMU identifier for userspace

[Joakim Zhang <qiangqing.zhang@xxxxxxx>]

The DDR Perf for i.MX8 is a system PMU whose axi id would different from
SoC to SoC. Need expose system PMU identifier for userspace which refer
to /sys/bus/event_source/devices/<PMU DEVICE>/identifier.

Signed-off-by: Joakim Zhang <qiangqing.zhang@xxxxxxx>
---
 drivers/perf/fsl_imx8_ddr_perf.c | 29 +++++++++++++++++++++++++++++
 1 file changed, 29 insertions(+)

diff --git a/drivers/perf/fsl_imx8_ddr_perf.c b/drivers/perf/fsl_imx8_ddr_perf.c
index 90884d14f95f..ba523a94f4d7 100644
--- a/drivers/perf/fsl_imx8_ddr_perf.c
+++ b/drivers/perf/fsl_imx8_ddr_perf.c
@@ -76,6 +76,7 @@ struct ddr_pmu {
 	unsigned int cpu;
 	struct	hlist_node node;
 	struct	device *dev;
+	const char *identifier;
 	struct perf_event *events[NUM_COUNTERS];
 	int active_events;
 	enum cpuhp_state cpuhp_state;
@@ -84,6 +85,27 @@ struct ddr_pmu {
 	int id;
 };
 
+static ssize_t ddr_perf_identifier_show(struct device *dev,
+					struct device_attribute *attr,
+					char *page)
+{
+	struct ddr_pmu *pmu = dev_get_drvdata(dev);
+
+	return sprintf(page, "%s\n", pmu->identifier);
+}
+
+static struct device_attribute ddr_perf_identifier_attr =
+	__ATTR(identifier, 0444, ddr_perf_identifier_show, NULL);
+
+static struct attribute *ddr_perf_identifier_attrs[] = {
+	&ddr_perf_identifier_attr.attr,
+	NULL,
+};
+
+static struct attribute_group ddr_perf_identifier_attr_group = {
+	.attrs = ddr_perf_identifier_attrs,
+};
+
 enum ddr_perf_filter_capabilities {
 	PERF_CAP_AXI_ID_FILTER = 0,
 	PERF_CAP_AXI_ID_FILTER_ENHANCED,
@@ -237,6 +259,7 @@ static const struct attribute_group *attr_groups[] = {
 	&ddr_perf_format_attr_group,
 	&ddr_perf_cpumask_attr_group,
 	&ddr_perf_filter_cap_attr_group,
+	&ddr_perf_identifier_attr_group,
 	NULL,
 };
 
@@ -601,6 +624,7 @@ static int ddr_perf_probe(struct platform_device *pdev)
 	struct ddr_pmu *pmu;
 	struct device_node *np;
 	void __iomem *base;
+	const char *identifier = NULL;
 	char *name;
 	int num;
 	int ret;
@@ -620,6 +644,11 @@ static int ddr_perf_probe(struct platform_device *pdev)
 
 	platform_set_drvdata(pdev, pmu);
 
+	ret = of_property_read_string(np, "identifier", &identifier);
+	if (ret < 0)
+		dev_warn(&pdev->dev, "Failed to get identifier\n");
+	pmu->identifier = identifier;
+
 	name = devm_kasprintf(&pdev->dev, GFP_KERNEL, DDR_PERF_DEV_NAME "%d",
 			      num);
 	if (!name)
-- 
2.17.1