usb: gadget: uvc: add trace of enqueued and completed requests

This patch is adding trace events for each request that is being
enqueued into the hw and will be completed. This way it is possible
to track the fill status of the gadget hardware and find potential
issues.

Signed-off-by: Michael Grzeschik <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Greg Kroah-Hartman <[e-mail]>

drivers/usb/gadget/function/Makefile

···
 usb_f_uac2-y			:= f_uac2.o
 obj-$(CONFIG_USB_F_UAC2)	+= usb_f_uac2.o
 usb_f_uvc-y			:= f_uvc.o uvc_queue.o uvc_v4l2.o uvc_video.o uvc_configfs.o
+ifneq ($(CONFIG_TRACING),)
+    CFLAGS_uvc_trace.o		:= -I$(src)
+    usb_f_uvc-y			+= uvc_trace.o
+endif
 obj-$(CONFIG_USB_F_UVC)		+= usb_f_uvc.o
 usb_f_midi-y			:= f_midi.o
 obj-$(CONFIG_USB_F_MIDI)	+= usb_f_midi.o

drivers/usb/gadget/function/uvc_trace.c

···
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * trace.c - USB UVC Gadget Trace Support
+ *
+ * Copyright (C) 2024 Pengutronix e.K.
+ *
+ * Author: Michael Grzeschik <[e-mail]>
+ */
+
+#define CREATE_TRACE_POINTS
+#include "uvc_trace.h"

drivers/usb/gadget/function/uvc_trace.h

···
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * trace.h - USB UVC Gadget Trace Support
+ *
+ * Copyright (C) 2024 Pengutronix e.K.
+ *
+ * Author: Michael Grzeschik <[e-mail]>
+ */
+
+#undef TRACE_SYSTEM
+#define TRACE_SYSTEM uvcg
+
+#if !defined(__UVCG_TRACE_H) || defined(TRACE_HEADER_MULTI_READ)
+#define __UVCG_TRACE_H
+
+#include <linux/types.h>
+#include <linux/tracepoint.h>
+#include <linux/usb/gadget.h>
+#include <asm/byteorder.h>
+
+DECLARE_EVENT_CLASS(uvcg_video_req,
+	TP_PROTO(struct usb_request *req, u32 queued),
+	TP_ARGS(req, queued),
+	TP_STRUCT__entry(
+		__field(struct usb_request *, req)
+		__field(u32, length)
+		__field(u32, queued)
+	),
+	TP_fast_assign(
+		__entry->req = req;
+		__entry->length = req->length;
+		__entry->queued = queued;
+	),
+	TP_printk("req %p length %u queued %u",
+		__entry->req,
+		__entry->length,
+		__entry->queued)
+);
+
+DEFINE_EVENT(uvcg_video_req, uvcg_video_complete,
+	TP_PROTO(struct usb_request *req, u32 queued),
+	TP_ARGS(req, queued)
+);
+
+DEFINE_EVENT(uvcg_video_req, uvcg_video_queue,
+	TP_PROTO(struct usb_request *req, u32 queued),
+	TP_ARGS(req, queued)
+);
+
+#endif /* __UVCG_TRACE_H */
+
+/* this part has to be here */
+
+#undef TRACE_INCLUDE_PATH
+#define TRACE_INCLUDE_PATH .
+
+#undef TRACE_INCLUDE_FILE
+#define TRACE_INCLUDE_FILE uvc_trace
+
+#include <trace/define_trace.h>

drivers/usb/gadget/function/uvc_video.c

···
 #include "uvc.h"
 #include "uvc_queue.h"
 #include "uvc_video.h"
+#include "uvc_trace.h"
 
 /* --------------------------------------------------------------------------
  * Video codecs
···
 
 	atomic_inc(&video->queued);
 
+	trace_uvcg_video_queue(req, atomic_read(&video->queued));
+
 	return ret;
 }
 
···
 	 * happen. Since there are is a new free request wake up the pump.
 	 */
 	queue_work(video->async_wq, &video->pump);
+
+	trace_uvcg_video_complete(req, atomic_read(&video->queued));
 
 	spin_unlock_irqrestore(&video->req_lock, flags);