V4L/DVB (9166): ivtv - Fix potential race condition in yuv handler

Modified yuv register update handling to remove a potential race condition
which could occur with the first video frame.

Also removed a forced yuv position update, since changing the source video
dimensions or interlace settings doesn't affect the frame already being
displayed.

Signed-off-by: Ian Armstrong <[e-mail]>
Signed-off-by: Hans Verkuil <[e-mail]>
Signed-off-by: Mauro Carvalho Chehab <[e-mail]>

drivers/media/video/ivtv/ivtv-driver.h

···
 	struct v4l2_rect main_rect;
 	u32 v4l2_src_w;
 	u32 v4l2_src_h;
+
+	u8 running; /* Have any frames been displayed */
 };
 
 #define IVTV_VBI_FRAMES 32

drivers/media/video/ivtv/ivtv-ioctl.c

···
 		itv->dma_data_req_size =
 			1080 * ((yi->v4l2_src_h + 31) & ~31);
 
-	/* Force update of yuv registers */
-	yi->yuv_forced_update = 1;
 	return 0;
 }
 

drivers/media/video/ivtv/ivtv-irq.c

···
 	 */
 	unsigned int frame = read_reg(0x28c0) & 1;
 	struct yuv_playback_info *yi = &itv->yuv_info;
-	int last_dma_frame = atomic_read(&itv->yuv_info.next_dma_frame);
+	int last_dma_frame = atomic_read(&yi->next_dma_frame);
 	struct yuv_frame_info *f = &yi->new_frame_info[last_dma_frame];
 
 	if (0) IVTV_DEBUG_IRQ("DEC VSYNC\n");
···
 				next_dma_frame = (next_dma_frame + 1) % IVTV_YUV_BUFFERS;
 				atomic_set(&yi->next_dma_frame, next_dma_frame);
 				yi->fields_lapsed = -1;
+				yi->running = 1;
 			}
 		}
 	}
···
 		}
 
 		/* Check if we need to update the yuv registers */
-		if ((yi->yuv_forced_update || f->update) && last_dma_frame != -1) {
+		if (yi->running && (yi->yuv_forced_update || f->update)) {
 			if (!f->update) {
-				last_dma_frame = (u8)(last_dma_frame - 1) % IVTV_YUV_BUFFERS;
+				last_dma_frame =
+					(u8)(atomic_read(&yi->next_dma_frame) -
+						 1) % IVTV_YUV_BUFFERS;
 				f = &yi->new_frame_info[last_dma_frame];
 			}
 

drivers/media/video/ivtv/ivtv-yuv.c

···
 	IVTV_DEBUG_YUV("ivtv_yuv_close\n");
 	ivtv_waitq(&itv->vsync_waitq);
 
+	yi->running = 0;
 	atomic_set(&yi->next_dma_frame, -1);
 	atomic_set(&yi->next_fill_frame, 0);