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From:   Jae Hyun Yoo <quic_jaehyoo@quicinc.com>
To:     Wolfram Sang <wsa@kernel.org>,
        Steven Rostedt <rostedt@goodmis.org>,
        "Ingo Molnar" <mingo@redhat.com>
CC:     Jamie Iles <quic_jiles@quicinc.com>,
        Graeme Gregory <quic_ggregory@quicinc.com>,
        <linux-kernel@vger.kernel.org>, <linux-i2c@vger.kernel.org>,
        Jae Hyun Yoo <quic_jaehyoo@quicinc.com>
Subject: [PATCH v3] i2c: add tracepoints for I2C slave events
Date:   Fri, 18 Mar 2022 13:41:33 -0700
Message-ID: <20220318204133.657568-1-quic_jaehyoo@quicinc.com>
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I2C slave events tracepoints can be enabled by:

	echo 1 > /sys/kernel/tracing/events/i2c_slave/enable

and logs in /sys/kernel/tracing/trace will look like:

	... i2c_slave: i2c-0 a=010 ret=0 WR_REQ []
	... i2c_slave: i2c-0 a=010 ret=0 WR_RCV [02]
	... i2c_slave: i2c-0 a=010 ret=0 WR_RCV [0c]
	... i2c_slave: i2c-0 a=010 ret=0   STOP []
	... i2c_slave: i2c-0 a=010 ret=0 RD_REQ [04]
	... i2c_slave: i2c-0 a=010 ret=0 RD_PRO [b4]
	... i2c_slave: i2c-0 a=010 ret=0  STOP []

formatted as:

	i2c-<adapter_nr>
	a=<addr>
	ret=<ret>	<- callback return value
	<event>
	[<data>]

trace printings can be selected by adding a filter like:

	echo adapter_nr==1 >/sys/kernel/tracing/events/i2c_slave/filter

Signed-off-by: Jae Hyun Yoo <quic_jaehyoo@quicinc.com>
---
Changes in v3:
* Made trace print even when a callback return value is non-zero and print
  out the value too (Wolfram)
* Added TRACE_DEFINE_ENUM export for events to make it useful for perf and
  trace-cmd (Steven)

Changes in v2:
* Fixed trace_2c_slave call condition to optimize conditional compare logic
  (Steven)
* Fixed TP entry order to prevent wasting spaces in the ring buffer (Steven)
* Replaced __get_dynamic_array with __array for storing 1-length data value
  to make it faster and save space (Steven)

 drivers/i2c/i2c-core-slave.c     | 15 +++++++
 include/linux/i2c.h              |  8 +---
 include/trace/events/i2c_slave.h | 67 ++++++++++++++++++++++++++++++++
 3 files changed, 84 insertions(+), 6 deletions(-)
 create mode 100644 include/trace/events/i2c_slave.h

diff --git a/drivers/i2c/i2c-core-slave.c b/drivers/i2c/i2c-core-slave.c
index 1589179d5eb9..e3765e12f93b 100644
--- a/drivers/i2c/i2c-core-slave.c
+++ b/drivers/i2c/i2c-core-slave.c
@@ -14,6 +14,9 @@
 
 #include "i2c-core.h"
 
+#define CREATE_TRACE_POINTS
+#include <trace/events/i2c_slave.h>
+
 int i2c_slave_register(struct i2c_client *client, i2c_slave_cb_t slave_cb)
 {
 	int ret;
@@ -79,6 +82,18 @@ int i2c_slave_unregister(struct i2c_client *client)
 }
 EXPORT_SYMBOL_GPL(i2c_slave_unregister);
 
+int i2c_slave_event(struct i2c_client *client,
+		    enum i2c_slave_event event, u8 *val)
+{
+	int ret = client->slave_cb(client, event, val);
+
+	if (trace_i2c_slave_enabled())
+		trace_i2c_slave(client, event, val, ret);
+
+	return ret;
+}
+EXPORT_SYMBOL_GPL(i2c_slave_event);
+
 /**
  * i2c_detect_slave_mode - detect operation mode
  * @dev: The device owning the bus
diff --git a/include/linux/i2c.h b/include/linux/i2c.h
index 7d4f52ceb7b5..fbda5ada2afc 100644
--- a/include/linux/i2c.h
+++ b/include/linux/i2c.h
@@ -392,12 +392,8 @@ enum i2c_slave_event {
 int i2c_slave_register(struct i2c_client *client, i2c_slave_cb_t slave_cb);
 int i2c_slave_unregister(struct i2c_client *client);
 bool i2c_detect_slave_mode(struct device *dev);
-
-static inline int i2c_slave_event(struct i2c_client *client,
-				  enum i2c_slave_event event, u8 *val)
-{
-	return client->slave_cb(client, event, val);
-}
+int i2c_slave_event(struct i2c_client *client,
+		    enum i2c_slave_event event, u8 *val);
 #else
 static inline bool i2c_detect_slave_mode(struct device *dev) { return false; }
 #endif
diff --git a/include/trace/events/i2c_slave.h b/include/trace/events/i2c_slave.h
new file mode 100644
index 000000000000..811166abbe3a
--- /dev/null
+++ b/include/trace/events/i2c_slave.h
@@ -0,0 +1,67 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+/*
+ * I2C slave tracepoints
+ *
+ * Copyright (c) 2022 Qualcomm Innovation Center, Inc. All rights reserved.
+ */
+#undef TRACE_SYSTEM
+#define TRACE_SYSTEM i2c_slave
+
+#if !defined(_TRACE_I2C_SLAVE_H) || defined(TRACE_HEADER_MULTI_READ)
+#define _TRACE_I2C_SLAVE_H
+
+#include <linux/i2c.h>
+#include <linux/tracepoint.h>
+
+TRACE_DEFINE_ENUM(I2C_SLAVE_READ_REQUESTED);
+TRACE_DEFINE_ENUM(I2C_SLAVE_WRITE_REQUESTED);
+TRACE_DEFINE_ENUM(I2C_SLAVE_READ_PROCESSED);
+TRACE_DEFINE_ENUM(I2C_SLAVE_WRITE_RECEIVED);
+TRACE_DEFINE_ENUM(I2C_SLAVE_STOP);
+
+#define show_event_type(type)						\
+	__print_symbolic(type,						\
+		{ I2C_SLAVE_READ_REQUESTED,	"RD_REQ" },		\
+		{ I2C_SLAVE_WRITE_REQUESTED,	"WR_REQ" },		\
+		{ I2C_SLAVE_READ_PROCESSED,	"RD_PRO" },		\
+		{ I2C_SLAVE_WRITE_RECEIVED,	"WR_RCV" },		\
+		{ I2C_SLAVE_STOP,		"  STOP" })
+
+TRACE_EVENT(i2c_slave,
+	TP_PROTO(const struct i2c_client *client, enum i2c_slave_event event,
+		 __u8 *val, int cb_ret),
+	TP_ARGS(client, event, val, cb_ret),
+	TP_STRUCT__entry(
+		__field(int,				adapter_nr	)
+		__field(int,				ret		)
+		__field(__u16,				addr		)
+		__field(__u16,				len		)
+		__field(enum i2c_slave_event,		event		)
+		__array(__u8,				buf,	1)	),
+
+	TP_fast_assign(
+		__entry->adapter_nr = client->adapter->nr;
+		__entry->addr = client->addr;
+		__entry->event = event;
+		__entry->ret = cb_ret;
+		switch (event) {
+		case I2C_SLAVE_READ_REQUESTED:
+		case I2C_SLAVE_READ_PROCESSED:
+		case I2C_SLAVE_WRITE_RECEIVED:
+			__entry->len = 1;
+			memcpy(__entry->buf, val, __entry->len);
+			break;
+		default:
+			__entry->len = 0;
+			break;
+		}
+		),
+	TP_printk("i2c-%d a=%03x ret=%d %s [%*phD]",
+		__entry->adapter_nr, __entry->addr, __entry->ret,
+		show_event_type(__entry->event), __entry->len, __entry->buf
+		));
+
+#endif /* _TRACE_I2C_SLAVE_H */
+
+/* This part must be outside protection */
+#include <trace/define_trace.h>
-- 
2.25.1