spmi: add command tracepoints for SPMI

Add tracepoints to retrieve information about read, write
and non-data commands. For performance measurement support
tracepoints are added at the beginning and at the end of
transfers. Following is a list showing the new tracepoint
events. The "cmd" parameter here represents the opcode, SID,
and full 16-bit address.

spmi_write_begin: cmd and data buffer.
spmi_write_end  : cmd and return value.
spmi_read_begin : cmd.
spmi_read_end   : cmd, return value and data buffer.
spmi_cmd        : cmd.

The reason that cmd appears at both the beginning and at
the end event is that SPMI drivers can request commands
concurrently. cmd helps in matching the corresponding
events.

SPMI tracepoints can be enabled like:

echo 1 >/sys/kernel/debug/tracing/events/spmi/enable

and will dump messages that can be viewed in
/sys/kernel/debug/tracing/trace that look like:

... spmi_read_begin: opc=56 sid=00 addr=0x0000
... spmi_read_end: opc=56 sid=00 addr=0x0000 ret=0 len=02 buf=0x[01-40]
... spmi_write_begin: opc=48 sid=00 addr=0x0000 len=3 buf=0x[ff-ff-ff]

Suggested-by: Sagar Dharia <sdharia@codeaurora.org>
Acked-by: Steven Rostedt <rostedt@goodmis.org>
Reviewed-by: Stephen Boyd <sboyd@codeaurora.org>
Signed-off-by: Gilad Avidov <gavidov@codeaurora.org>
Signed-off-by: Ankit Gupta <ankgupta@codeaurora.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/spmi/spmi.c

@@ -22,6 +22,8 @@
 #include <linux/pm_runtime.h>
 
 #include <dt-bindings/spmi/spmi.h>
+#define CREATE_TRACE_POINTS
+#include <trace/events/spmi.h>
 
 static DEFINE_IDA(ctrl_ida);
 
@@ -96,28 +98,42 @@ EXPORT_SYMBOL_GPL(spmi_device_remove);
 static inline int
 spmi_cmd(struct spmi_controller *ctrl, u8 opcode, u8 sid)
 {
+	int ret;
+
 	if (!ctrl || !ctrl->cmd || ctrl->dev.type != &spmi_ctrl_type)
 		return -EINVAL;
 
-	return ctrl->cmd(ctrl, opcode, sid);
+	ret = ctrl->cmd(ctrl, opcode, sid);
+	trace_spmi_cmd(opcode, sid, ret);
+	return ret;
 }
 
 static inline int spmi_read_cmd(struct spmi_controller *ctrl, u8 opcode,
 				u8 sid, u16 addr, u8 *buf, size_t len)
 {
+	int ret;
+
 	if (!ctrl || !ctrl->read_cmd || ctrl->dev.type != &spmi_ctrl_type)
 		return -EINVAL;
 
-	return ctrl->read_cmd(ctrl, opcode, sid, addr, buf, len);
+	trace_spmi_read_begin(opcode, sid, addr);
+	ret = ctrl->read_cmd(ctrl, opcode, sid, addr, buf, len);
+	trace_spmi_read_end(opcode, sid, addr, ret, len, buf);
+	return ret;
 }
 
 static inline int spmi_write_cmd(struct spmi_controller *ctrl, u8 opcode,
 				 u8 sid, u16 addr, const u8 *buf, size_t len)
 {
+	int ret;
+
 	if (!ctrl || !ctrl->write_cmd || ctrl->dev.type != &spmi_ctrl_type)
 		return -EINVAL;
 
-	return ctrl->write_cmd(ctrl, opcode, sid, addr, buf, len);
+	trace_spmi_write_begin(opcode, sid, addr, len, buf);
+	ret = ctrl->write_cmd(ctrl, opcode, sid, addr, buf, len);
+	trace_spmi_write_end(opcode, sid, addr, ret);
+	return ret;
 }
 
 /**