[PATCH 2/2] powerpc/hv-24x7: Add sysfs files inside hv-24x7 device to show cpumask

[Kajol Jain]

Patch here adds a cpumask attr to hv_24x7 pmu along with ABI documentation.

command:# cat /sys/devices/hv_24x7/cpumask
0

Signed-off-by: Kajol Jain <kj...@linux.ibm.com>
---
 .../sysfs-bus-event_source-devices-hv_24x7    |  6 ++++
 arch/powerpc/perf/hv-24x7.c                   | 31 ++++++++++++++++++-
 2 files changed, 36 insertions(+), 1 deletion(-)

diff --git a/Documentation/ABI/testing/sysfs-bus-event_source-devices-hv_24x7 
b/Documentation/ABI/testing/sysfs-bus-event_source-devices-hv_24x7
index e8698afcd952..281e7b367733 100644
--- a/Documentation/ABI/testing/sysfs-bus-event_source-devices-hv_24x7
+++ b/Documentation/ABI/testing/sysfs-bus-event_source-devices-hv_24x7
@@ -43,6 +43,12 @@ Description: read only
                This sysfs interface exposes the number of cores per chip
                present in the system.
 
+What:          /sys/devices/hv_24x7/cpumask
+Date:          June 2020
+Contact:       Linux on PowerPC Developer List <linuxppc-dev@lists.ozlabs.org>
+Description:   read only
+               This sysfs file exposes cpumask.
+
 What:          /sys/bus/event_source/devices/hv_24x7/event_descs/<event-name>
 Date:          February 2014
 Contact:       Linux on PowerPC Developer List <linuxppc-dev@lists.ozlabs.org>
diff --git a/arch/powerpc/perf/hv-24x7.c b/arch/powerpc/perf/hv-24x7.c
index fdc4ae155d60..03d870a9fc36 100644
--- a/arch/powerpc/perf/hv-24x7.c
+++ b/arch/powerpc/perf/hv-24x7.c
@@ -448,6 +448,12 @@ static ssize_t device_show_string(struct device *dev,
        return sprintf(buf, "%s\n", (char *)d->var);
 }
 
+static ssize_t cpumask_get_attr(struct device *dev,
+                               struct device_attribute *attr, char *buf)
+{
+       return cpumap_print_to_pagebuf(true, buf, &hv_24x7_cpumask);
+}
+
 static ssize_t sockets_show(struct device *dev,
                            struct device_attribute *attr, char *buf)
 {
@@ -1116,6 +1122,17 @@ static DEVICE_ATTR_RO(sockets);
 static DEVICE_ATTR_RO(chipspersocket);
 static DEVICE_ATTR_RO(coresperchip);
 
+static DEVICE_ATTR(cpumask, S_IRUGO, cpumask_get_attr, NULL);
+
+static struct attribute *cpumask_attrs[] = {
+       &dev_attr_cpumask.attr,
+       NULL,
+};
+
+static struct attribute_group cpumask_attr_group = {
+       .attrs = cpumask_attrs,
+};
+
 static struct bin_attribute *if_bin_attrs[] = {
        &bin_attr_catalog,
        NULL,
@@ -1143,6 +1160,11 @@ static const struct attribute_group *attr_groups[] = {
        &event_desc_group,
        &event_long_desc_group,
        &if_group,
+       /*
+        * This NULL is a placeholder for the cpumask attr which will update
+        * onlyif cpuhotplug registration is successful
+        */
+       NULL,
        NULL,
 };
 
@@ -1727,8 +1749,15 @@ static int hv_24x7_init(void)
 
        /* init cpuhotplug */
        r = hv_24x7_cpu_hotplug_init();
-       if (r)
+       if (r) {
                pr_err("hv_24x7: CPU hotplug init failed\n");
+       } else {
+               /*
+                * Cpu hotplug init is successful, add the
+                * cpumask file as part of pmu attr group
+                */
+               attr_groups[5] = &cpumask_attr_group;
+       }
 
        r = perf_pmu_register(&h_24x7_pmu, h_24x7_pmu.name, -1);
        if (r)
-- 
2.18.2