qcom-charger: add support to watch storm of events

Storm watch provides a simple API for tracking the occurrence of event
storms.

An event storm is defined as a cluster of events where there are
X events with no more than Y milliseconds between them, where X and Y
are configurable per event.

Querying whether a storm has occurred marks a new event.

Change-Id: Idf4bb1421d0dbec295f92f84174cd4bbc6130250
Signed-off-by: Nicholas Troast <ntroast@codeaurora.org>

drivers/power/qcom-charger/Makefile

@@ -6,6 +6,6 @@ obj-$(CONFIG_SMB1351_USB_CHARGER) += smb1351-charger.o pmic-voter.o
 obj-$(CONFIG_MSM_BCL_CTL)	+= msm_bcl.o
 obj-$(CONFIG_MSM_BCL_PERIPHERAL_CTL) += bcl_peripheral.o
 obj-$(CONFIG_BATTERY_BCL) += battery_current_limit.o
-obj-$(CONFIG_QPNP_SMB2)		+= qpnp-smb2.o smb-lib.o pmic-voter.o
-obj-$(CONFIG_SMB138X_CHARGER)	+= smb138x-charger.o smb-lib.o pmic-voter.o
+obj-$(CONFIG_QPNP_SMB2)		+= qpnp-smb2.o smb-lib.o pmic-voter.o storm-watch.o
+obj-$(CONFIG_SMB138X_CHARGER)	+= smb138x-charger.o smb-lib.o pmic-voter.o storm-watch.o
 obj-$(CONFIG_QPNP_QNOVO)	+= qpnp-qnovo.o

drivers/power/qcom-charger/storm-watch.c

@@ -0,0 +1,57 @@
+/* Copyright (c) 2016 The Linux Foundation. All rights reserved.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 and
+ * only version 2 as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ */
+
+#include "storm-watch.h"
+
+/**
+ * is_storming(): Check if an event is storming
+ *
+ * @data: Data for tracking an event storm
+ *
+ * The return value will be true if a storm has been detected and
+ * false if a storm was not detected.
+ */
+bool is_storming(struct storm_watch *data)
+{
+	ktime_t curr_kt, delta_kt;
+	bool is_storming = false;
+
+	if (!data)
+		return false;
+
+	if (!data->enabled)
+		return false;
+
+	/* max storm count must be greater than 0 */
+	if (data->max_storm_count <= 0)
+		return false;
+
+	/* the period threshold must be greater than 0ms */
+	if (data->storm_period_ms <= 0)
+		return false;
+
+	curr_kt = ktime_get_boottime();
+	delta_kt = ktime_sub(curr_kt, data->last_kt);
+
+	if (ktime_to_ms(delta_kt) < data->storm_period_ms)
+		data->storm_count++;
+	else
+		data->storm_count = 0;
+
+	if (data->storm_count > data->max_storm_count) {
+		is_storming = true;
+		data->storm_count = 0;
+	}
+
+	data->last_kt = curr_kt;
+	return is_storming;
+}

drivers/power/qcom-charger/storm-watch.h

@@ -0,0 +1,36 @@
+/* Copyright (c) 2016 The Linux Foundation. All rights reserved.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 and
+ * only version 2 as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ */
+
+#ifndef __STORM_WATCH_H
+#define __STORM_WATCH_H
+#include <linux/ktime.h>
+
+/**
+ * Data used to track an event storm.
+ *
+ * @storm_period_ms: The maximum time interval between two events. If this limit
+ *                   is exceeded then the event chain will be broken and removed
+ *                   from consideration for a storm.
+ * @max_storm_count: The number of chained events required to trigger a storm.
+ * @storm_count:     The current number of chained events.
+ * @last_kt:         Kernel time of the last event seen.
+ */
+struct storm_watch {
+	bool	enabled;
+	int	storm_period_ms;
+	int	max_storm_count;
+	int	storm_count;
+	ktime_t	last_kt;
+};
+
+bool is_storming(struct storm_watch *data);
+#endif