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

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Date:   Thu,  2 Mar 2017 05:50:00 -0500
From:   Anurup M <anurupvasu@...il.com>
To:     mark.rutland@....com, will.deacon@....com
Cc:     linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        anurup.m@...wei.com, zhangshaokun@...ilicon.com,
        tanxiaojun@...wei.com, xuwei5@...ilicon.com,
        sanil.kumar@...ilicon.com, john.garry@...wei.com,
        gabriele.paoloni@...wei.com, shiju.jose@...wei.com,
        huangdaode@...ilicon.com, linuxarm@...wei.com,
        dikshit.n@...wei.com, shyju.pv@...wei.com, anurupvasu@...il.com
Subject: [PATCH v5 10/11] drivers: perf: hisi: use poll method when no IRQ for MN counter overflow

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@...wei.com>
Signed-off-by: Shaokun Zhang <zhangshaokun@...ilicon.com>
Signed-off-by: Dikshit N <dikshit.n@...wei.com>
---
 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