[media] vivid: add support for reduced fps in video out

If reduced fps flag is set then check if other necessary conditions
are true for the given bt timing. If yes, then reduce the frame rate.
For vivid transmitter, timeperframe_vid_out controls the frame rate.
Adjusting the timeperframe_vid_out by scaling down pixel clock by
factor of 1000 / 1001.

Signed-off-by: Prashant Laddha <prladdha@cisco.com>
Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>

drivers/media/platform/vivid/vivid-vid-out.c

@@ -224,6 +224,7 @@ void vivid_update_format_out(struct vivid_dev *dev)
 {
 	struct v4l2_bt_timings *bt = &dev->dv_timings_out.bt;
 	unsigned size, p;
+	u64 pixelclock;
 
 	switch (dev->output_type[dev->output]) {
 	case SVID:
@@ -245,8 +246,14 @@ void vivid_update_format_out(struct vivid_dev *dev)
 		dev->sink_rect.width = bt->width;
 		dev->sink_rect.height = bt->height;
 		size = V4L2_DV_BT_FRAME_WIDTH(bt) * V4L2_DV_BT_FRAME_HEIGHT(bt);
+
+		if (can_reduce_fps(bt) && (bt->flags & V4L2_DV_FL_REDUCED_FPS))
+			pixelclock = div_u64(bt->pixelclock * 1000, 1001);
+		else
+			pixelclock = bt->pixelclock;
+
 		dev->timeperframe_vid_out = (struct v4l2_fract) {
-			size / 100, (u32)bt->pixelclock / 100
+			size / 100, (u32)pixelclock / 100
 		};
 		if (bt->interlaced)
 			dev->field_out = V4L2_FIELD_ALTERNATE;