[PATCH v5 10/11] drivers: perf: hisi: use poll method when no IRQ for MN counter overflow

From: Anurup M
Date: Thu Mar 02 2017 - 07:43:06 EST


When no IRQ is supported in hardware, use hrtimer to poll and
update event counter and avoid overflow condition for MN PMU.
An interval of 8 seconds is used for the hrtimer.

Signed-off-by: Anurup M <anurup.m@xxxxxxxxxx>
Signed-off-by: Shaokun Zhang <zhangshaokun@xxxxxxxxxxxxx>
Signed-off-by: Dikshit N <dikshit.n@xxxxxxxxxx>
---
drivers/perf/hisilicon/hisi_uncore_mn.c | 39 +++++++++++++++++++++++++++++++++
1 file changed, 39 insertions(+)

diff --git a/drivers/perf/hisilicon/hisi_uncore_mn.c b/drivers/perf/hisilicon/hisi_uncore_mn.c
index 9a09798..375996a 100644
--- a/drivers/perf/hisilicon/hisi_uncore_mn.c
+++ b/drivers/perf/hisilicon/hisi_uncore_mn.c
@@ -20,6 +20,8 @@
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
#include <linux/bitmap.h>
+#include <linux/hrtimer.h>
+#include <linux/ktime.h>
#include <linux/module.h>
#include <linux/of.h>
#include <linux/of_device.h>
@@ -56,6 +58,15 @@ enum armv8_hisi_mn_counters {

#define GET_MODULE_ID(hwmod_data) hwmod_data->mn_hwcfg.module_id

+/*
+ * Default timer frequency to poll and avoid counter overflow.
+ * CPU speed = 2.4Ghz and number of CPU cores in a SCCL is 16.
+ * For a single MN event on a CPU core consumes 200 cycles.
+ * So overflow time = (2^31 * 200) / (16 * 2.4G) which is about 21 seconds
+ * So on a safe side we use a timer interval of 8sec
+ */
+#define MN1_HRTIMER_INTERVAL (8LL * MSEC_PER_SEC)
+
struct hisi_mn_hwcfg {
u32 module_id;
};
@@ -272,6 +283,15 @@ static const struct of_device_id mn_of_match[] = {
};
MODULE_DEVICE_TABLE(of, mn_of_match);

+/* Use hrtimer when no IRQ, to poll for avoiding counter overflow */
+static void hisi_mn_hrtimer_init(struct hisi_pmu *mn_pmu)
+{
+ INIT_LIST_HEAD(&mn_pmu->active_list);
+ mn_pmu->ops->start_hrtimer = hisi_hrtimer_start;
+ mn_pmu->ops->stop_hrtimer = hisi_hrtimer_stop;
+ hisi_hrtimer_init(mn_pmu, MN1_HRTIMER_INTERVAL);
+}
+
static int hisi_mn_init_data(struct hisi_pmu *mn_pmu,
struct hisi_djtag_client *client)
{
@@ -314,6 +334,12 @@ static int hisi_mn_init_data(struct hisi_pmu *mn_pmu,
} else
return -EINVAL;

+ /*
+ * Use poll method to avoid counter overflow as
+ * overflow IRQ is not supported in hardware.
+ */
+ hisi_mn_hrtimer_init(mn_pmu);
+
return 0;
}

@@ -361,11 +387,24 @@ static const struct attribute_group hisi_mn_cpumask_attr_group = {
.attrs = hisi_mn_cpumask_attrs,
};

+static DEVICE_ATTR(hrtimer_interval, 0444, hisi_hrtimer_interval_sysfs_show,
+ NULL);
+
+static struct attribute *hisi_mn_hrtimer_interval_attrs[] = {
+ &dev_attr_hrtimer_interval.attr,
+ NULL,
+};
+
+static const struct attribute_group hisi_mn_hrtimer_interval_attr_group = {
+ .attrs = hisi_mn_hrtimer_interval_attrs,
+};
+
static const struct attribute_group *hisi_mn_pmu_attr_groups[] = {
&hisi_mn_attr_group,
&hisi_mn_format_group,
&hisi_mn_events_group,
&hisi_mn_cpumask_attr_group,
+ &hisi_mn_hrtimer_interval_attr_group,
NULL,
};

--
2.1.4