usb: gadget: uvc: Switch to monotonic clock for buffer timestamps

The wall time clock isn't useful for applications as it can jump around
due to time adjustement. Switch to the monotonic clock.

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Hans Verkuil <hans.verkuil@cisco.com>
Acked-by: Felipe Balbi <balbi@ti.com>
Signed-off-by: Felipe Balbi <balbi@ti.com>

drivers/usb/gadget/uvc_queue.c

@@ -20,6 +20,7 @@
 #include <linux/vmalloc.h>
 #include <linux/wait.h>
 
+#include <media/v4l2-common.h>
 #include <media/videobuf2-vmalloc.h>
 
 #include "uvc.h"
@@ -379,14 +380,8 @@ static struct uvc_buffer *uvc_queue_next_buffer(struct uvc_video_queue *queue,
 	else
 		nextbuf = NULL;
 
-	/*
-	 * FIXME: with videobuf2, the sequence number or timestamp fields
-	 * are valid only for video capture devices and the UVC gadget usually
-	 * is a video output device. Keeping these until the specs are clear on
-	 * this aspect.
-	 */
 	buf->buf.v4l2_buf.sequence = queue->sequence++;
-	do_gettimeofday(&buf->buf.v4l2_buf.timestamp);
+	v4l2_get_timestamp(&buf->buf.v4l2_buf.timestamp);
 
 	vb2_set_plane_payload(&buf->buf, 0, buf->bytesused);
 	vb2_buffer_done(&buf->buf, VB2_BUF_STATE_DONE);