[PATCH] powerpc/perf: Add support for caps under sysfs in powerpc

[Athira Rajeev <atrajeev@linux.vnet.ibm.com>]

Add caps support under "/sys/bus/event_source/devices/<pmu>/"
for powerpc. This directory can be used to expose some of the
specific features that powerpc PMU supports to the user.
Example: pmu_name. The name of PMU registered will depend on
platform, say power9 or power10 or it could be Generic Compat
PMU.

Currently the only way to know which is the registered
PMU is from the dmesg logs. But clearing the dmesg will make it
difficult to know exact PMU backend used. And even extracting
from dmesg will be complicated, as we need  to parse the dmesg
logs and add filters for pmu name. Whereas by exposing it via
caps will make it easy as we just need to directly read it from
the sysfs.

Add a caps directory to /sys/bus/event_source/devices/cpu/
for power8, power9, power10 and generic compat PMU.

The information exposed currently:
 - pmu_name : Underlying PMU name from the driver

Example result with power9 pmu:

 # ls /sys/bus/event_source/devices/cpu/caps
pmu_name

 # cat /sys/bus/event_source/devices/cpu/caps/pmu_name
power9

Signed-off-by: Athira Rajeev <atrajeev@linux.vnet.ibm.com>
Reviewed-by: Madhavan Srinivasan <maddy@linux.ibm.com>
---
 arch/powerpc/perf/generic-compat-pmu.c | 20 ++++++++++++++++++++
 arch/powerpc/perf/power10-pmu.c        | 20 ++++++++++++++++++++
 arch/powerpc/perf/power8-pmu.c         | 20 ++++++++++++++++++++
 arch/powerpc/perf/power9-pmu.c         | 20 ++++++++++++++++++++
 4 files changed, 80 insertions(+)

diff --git a/arch/powerpc/perf/generic-compat-pmu.c b/arch/powerpc/perf/generic-compat-pmu.c
index f3db88aee4dd..7b5fe2d89007 100644
--- a/arch/powerpc/perf/generic-compat-pmu.c
+++ b/arch/powerpc/perf/generic-compat-pmu.c
@@ -151,9 +151,29 @@ static const struct attribute_group generic_compat_pmu_format_group = {
 	.attrs = generic_compat_pmu_format_attr,
 };
 
+static ssize_t pmu_name_show(struct device *cdev,
+		struct device_attribute *attr,
+		char *buf)
+{
+	return snprintf(buf, PAGE_SIZE, "generic_compat_pmu");
+}
+
+static DEVICE_ATTR_RO(pmu_name);
+
+static struct attribute *generic_compat_pmu_caps_attrs[] = {
+	&dev_attr_pmu_name.attr,
+	NULL
+};
+
+static struct attribute_group generic_compat_pmu_caps_group = {
+	.name  = "caps",
+	.attrs = generic_compat_pmu_caps_attrs,
+};
+
 static const struct attribute_group *generic_compat_pmu_attr_groups[] = {
 	&generic_compat_pmu_format_group,
 	&generic_compat_pmu_events_group,
+	&generic_compat_pmu_caps_group,
 	NULL,
 };
 
diff --git a/arch/powerpc/perf/power10-pmu.c b/arch/powerpc/perf/power10-pmu.c
index d3398100a60f..a622ff783719 100644
--- a/arch/powerpc/perf/power10-pmu.c
+++ b/arch/powerpc/perf/power10-pmu.c
@@ -258,6 +258,25 @@ static const struct attribute_group power10_pmu_format_group = {
 	.attrs = power10_pmu_format_attr,
 };
 
+static ssize_t pmu_name_show(struct device *cdev,
+		struct device_attribute *attr,
+		char *buf)
+{
+	return snprintf(buf, PAGE_SIZE, "power10");
+}
+
+static DEVICE_ATTR_RO(pmu_name);
+
+static struct attribute *power10_pmu_caps_attrs[] = {
+	&dev_attr_pmu_name.attr,
+	NULL
+};
+
+static struct attribute_group power10_pmu_caps_group = {
+	.name  = "caps",
+	.attrs = power10_pmu_caps_attrs,
+};
+
 static const struct attribute_group *power10_pmu_attr_groups_dd1[] = {
 	&power10_pmu_format_group,
 	&power10_pmu_events_group_dd1,
@@ -267,6 +286,7 @@ static const struct attribute_group *power10_pmu_attr_groups_dd1[] = {
 static const struct attribute_group *power10_pmu_attr_groups[] = {
 	&power10_pmu_format_group,
 	&power10_pmu_events_group,
+	&power10_pmu_caps_group,
 	NULL,
 };
 
diff --git a/arch/powerpc/perf/power8-pmu.c b/arch/powerpc/perf/power8-pmu.c
index e37b1e714d2b..fbcd2bfa05ba 100644
--- a/arch/powerpc/perf/power8-pmu.c
+++ b/arch/powerpc/perf/power8-pmu.c
@@ -187,9 +187,29 @@ static const struct attribute_group power8_pmu_events_group = {
 	.attrs = power8_events_attr,
 };
 
+static ssize_t pmu_name_show(struct device *cdev,
+		struct device_attribute *attr,
+		char *buf)
+{
+	return snprintf(buf, PAGE_SIZE, "power8");
+}
+
+static DEVICE_ATTR_RO(pmu_name);
+
+static struct attribute *power8_pmu_caps_attrs[] = {
+	&dev_attr_pmu_name.attr,
+	NULL
+};
+
+static struct attribute_group power8_pmu_caps_group = {
+	.name  = "caps",
+	.attrs = power8_pmu_caps_attrs,
+};
+
 static const struct attribute_group *power8_pmu_attr_groups[] = {
 	&isa207_pmu_format_group,
 	&power8_pmu_events_group,
+	&power8_pmu_caps_group,
 	NULL,
 };
 
diff --git a/arch/powerpc/perf/power9-pmu.c b/arch/powerpc/perf/power9-pmu.c
index c9eb5232e68b..11f290b6287f 100644
--- a/arch/powerpc/perf/power9-pmu.c
+++ b/arch/powerpc/perf/power9-pmu.c
@@ -258,9 +258,29 @@ static const struct attribute_group power9_pmu_format_group = {
 	.attrs = power9_pmu_format_attr,
 };
 
+static ssize_t pmu_name_show(struct device *cdev,
+		struct device_attribute *attr,
+		char *buf)
+{
+	return snprintf(buf, PAGE_SIZE, "power9");
+}
+
+static DEVICE_ATTR_RO(pmu_name);
+
+static struct attribute *power9_pmu_caps_attrs[] = {
+	&dev_attr_pmu_name.attr,
+	NULL
+};
+
+static struct attribute_group power9_pmu_caps_group = {
+	.name  = "caps",
+	.attrs = power9_pmu_caps_attrs,
+};
+
 static const struct attribute_group *power9_pmu_attr_groups[] = {
 	&power9_pmu_format_group,
 	&power9_pmu_events_group,
+	&power9_pmu_caps_group,
 	NULL,
 };
 
-- 
2.31.1